INTEGRATED PEST MANAGEMENT MANUAL FOR MINNESOTA STRAWBERRY FIELDS. A Scouting and Management Guide for Key Strawberry Pests

Transcription

1 INTEGRATED PEST MANAGEMENT MANUAL FOR MINNESOTA STRAWBERRY FIELDS A Scouting and Management Guide for Key Strawberry Pests Minnesota Department of Agriculture September, 2007

2 Integrated Pest Management Manual for Min ne so ta Strawberry Fields, 2nd Edition 2007 Revised and rewritten by Thaddeus McCamant, Northland Community & Technical College, Detroit Lakes, MN. Acknowledgements The 2007 Manual was developed and published by the Minnesota Department of Agriculture. Funding for the revised 2007 Manual is provided through partnership agreements with the Minnesota Fruit and Vegetable Growers Association (MFVGA) and the United States Department of Agriculture Risk Management Agency (RMA). These institutions are equal opportunity providers. The following persons helped review and/or contributed to the 2nd Edition: Emily Hoover, University of Minnesota, Horticulture Department, St. Paul, MN Bill Jacobson, Pine Tree Apple Orchard, White Bear Lake, MN John Luhman, Minnesota Department of Agriculture, St. Paul, MN Steven Poppe, University of Minnesota, West Central Research and Outreach Center, Morris, MN Edited by: Jeanne Ciborowski, Minnesota Department of Agriculture [The following individuals were contributing authors to the 1 st Edition: Henry Fadamiro, formerly Minnesota Department of Agriculture; Thaddeus McCamant, Northland Community and Technical College, Detroit Lakes, MN; Suzanne Wold- Burkness, formerly University of Minnesota, St. Paul, MN; Terrance Nennich, University of Minnesota Extension, Crookston, MN; Jill MacKenzie, formerly University of Minnesota Extension.] For additional copies of this manual, contact: Minnesota Department of Agriculture Agricultural Development and Financial Assistance Division 625 Robert Street North St. Paul, MN Phone: In accordance with the Americans with Disablities Act, an alternative form of communication is available upon request. TTY:

3 Table of Contents 1. Introduction Pest Management Concepts and Definitions... 6 Pest Classification Beneficials and Biological Control Integrated Pest Management Cultural Practices Resistant Varieties Economic/Action Thresholds Pesticide Resistance Degree Days and Insect Pest Forecasting Forecasting Disease Infection Periods Forecasting Weed Emergence 3. Using Pesticides Safely Pest Scouting Pest Scouting Equipment Scouting Techniques 5. Strawberry Developmental Stages and Associated Pests Planting Year Planting to First Runners First Daughter Plants to Full Canopy Full Canopy to Dormancy Bearing Fields Early Spring Pre-bloom Full Bloom Green Fruit Ripe Fruit Post-harvest 6. Biology and Management of Select Insect Pests and Diseases of Strawberry INSECTS Tarnished Plant Bug Strawberry Bud Weevil Flower Thrips Twospotted Spider Mite Cyclamen Mite Slugs White Grubs DISEASES Gray Mold Anthracnose Leather Rot Root Diseases

4 7. Weed Management in Minnesota Strawberry Fields Problem Weeds in Minnesota Strawberry Fields Site Preparation/Rotation Out of Strawberries Weed Control During the Establishment Year Weed Control in Bearing Fields 8. IPM in Day Neutral Strawberries Tarnished Plant Bug Other Insect Pests Diseases Organic Options 9. Organic Systems for June Bearing Strawberries The Finke System - Single Year Cropping Organic Production Using Long Rotations 10. Red Raspberries Appendix 1: Pesticide Options for Strawberries - Overview Appendix 2: Herbicide Options for Strawberries - Planting Year (Establishment) Appendix 3: Herbicide Options for Stawberries - Production Years (Bearing) Appendix 4: Insecticides for Strawberries Appendix 5: Fungicides for Strawberries Appendix 6: References and Suggested Readings Appendix 7: Sources of Pest Management Supplies DISCLAIMER Reference to products in this publication is not intended to be an endorsement to the exclusion of others which may have similar uses. Any person using products listed in this publication assumes full responsibility for their use in accordance with current manufacturer directions. 4

5 1. Introduction STRAWBERRIES can be grown in all parts of Minnesota, from Lake of the Woods in the north to the bluffs of the Mississippi in the south. Demand for locally grown strawberries is high and increasing. Dozens of small farms throughout the state supplement their incomes while meeting the demand for healthy, locally grown berries. A well managed strawberry farm in a good location can gross more than $10,000 an acre. As a high value crop, strawberries also require high inputs. Production costs average $5,000 an acre, with the highest cost being weed control. Growers must also spend hundreds of dollars per acre on insect and disease control, or risk losing their crop. In conventional strawberry production, growers sprayed fungicides weekly from bloom through harvest. With Integrated Pest Management (IPM), growers use cultural practices to lower the pest pressure in their fields and spray when the insects or diseases are present at high enough levels to lower yield. In an IPM program, a grower must spend time monitoring his/her field, but the higher costs in labor and time are offset by lower pesticide costs, fewer environmental concerns and better control of some pests. Strawberry growers interested in adopting IPM can use the information in this manual to improve their skills on their own farms. Minnesota has a unique climate, with warm, humid summers, long, cold winters, and short springs. The developmental phenology of many pests is different than in places with milder winters or longer springs. The current manual is intended for use as a tool to aid Minnesota strawberry growers and growers from other Upper Midwest states in sampling, monitoring, and managing key insect, mite, disease, and weed pests. This publication incorporates research data collected in Minnesota during the past few years as well as tested IPM concepts and information from other sources. In dealing with pesticide information throughout this manual, our goal is not to endorse a particular product or trade name, but to merely indicate possible options to the grower or user. It is our hope that growers, academics, scientists, extension agents, industry representatives, private consultants, and other members of the fruit production community will find this manual useful and informative. Kendall Lorenz helping with the strawberry harvest. 5

6 2. Pest Management Concepts and Definitions Pest Classification Insects: Strawberry pests can be classified according to the part of the plant they infest or by their economic importance. Fruit and flower feeders include tarnished plant bugs, slugs, sap beetles, thrips, and strawberry bud weevils. Fruit feeders directly lower yields by reducing the number of fruit, reducing fruit size or making the fruit unmarketable. Leaf feeders such as leafrollers, leafhoppers, aphids, and mites reduce the plant s leaf area and reduce yields by lowering a plant s photosynthetic capacity. Root-feeding insects such as strawberry rootworm, root weevils, and white grubs attack and damage strawberry roots and either stunt or kill plants. Insect pests can also be classified in terms of the seriousness of their infestation. Key pests cause major damage on a regular basis unless controlled. Occasional pests become intolerable only irregularly due to climate or a change in environment. Secondary pests can be tolerated in small numbers and do not need to be controlled every year. Secondary pests can become important after broad spectrum insecticides kill beneficial insects. Diseases: Strawberry diseases can also be classified according to the part of the plant infected. Fruit diseases include gray mold, anthracnose, and leather rot. Leaf spot, leaf scorch, and leaf blight lower yields by reducing leaf area. Diseases such as red stele, black root rot, and verticillium wilt damage root systems, causing stunted or dead plants. Beneficials and Biological Control Most insects, mites, fungi and bacteria living in a strawberry field are either benign or beneficial. Benign organisms neither directly help nor harm berry plants, like the fungi that break down the straw each summer. Beneficial insects include insects that feed on insect pests or bees that aid pollination and assure fruit set. Beneficial fungi and bacteria help strawberry plants absorb nutrients from the soil and protect plants from diseases. Two important groups of beneficials are the predators, and parasitoids. Predators attack or kill a pest (e.g. lady beetles, syrphid flies, lacewings, ants, spiders, and predator mites). Parasitoids are small wasps that lay their eggs in insect eggs, larvae, pupae or in aphids. The larvae hatch in the host, feed and grow inside the host and eventually kill it. Many insects do not fit neatly into the categories of beneficial, benign or pest. Some insects can be beneficial at one time of year and turn into a pest at another time of year, such as yellow jackets which eat caterpillars in midsummer, but feed on fruit in late summer. Others, such as the Polydrosus beetle, are benign at low levels, but can harm a strawberry field if the plants are weak and the beetle population is high. Scientists have yet to assign a role to most of the insects and mites living in a strawberry field. Strawberry growers should try to increase the population of natural enemies to common pests through introduction, augmentation, or conservation techniques. Introduction is releasing predators or parasites that are not living in the field. Augmentation is releasing natural enemies to boost existing populations. Conservation is manipulating habitat and resources to conserve or enhance natural enemy numbers. Beneficials will thrive if growers spray insecticides only when needed, time their sprays accurately, or select pesticides that are least toxic to beneficials. Many broad spectrum insecticides kill minor pests, secondary pests and beneficials. Under an integrated pest management program, broad spectrum insecticides are used sparingly and secondary pests are carefully monitored and managed to preserve beneficials. 6

7 Integrated Pest Management Integrated pest management (IPM) coordinates the use of pest biology, environmental information and available technology to prevent unacceptable levels of pest damage by the most economical means, while posing the least possible risk to people and the environment. IPM strategies include planting pest-resistant varieties, pest scouting, pest forecasting, cultural control, physical control, biological control, and judicious pesticide use. Synthetic pesticides can be used in an IPM program when no other options are available and the pesticides do not eradicate benign or beneficial organisms. By using multiple control strategies, pests are less likely to develop resistance to one particular strategy. The goal of IPM is to produce high quality, safe fruit in a cost-effective manner without significant adverse effects on the environment. IPM began when growers and scientists realized that most insect problems did not disappear under conventional pest control. Growers who practice IPM don t try to eliminate all pests, but rather try to suppress pest populations to levels that do not cause economic damage rather than eradicate all insects. IPM requires a knowledge of pests and the coordination of all fruit production components. Growers who want to develop an IPM program should develop the following skills and knowledge: Learn to identify insect and disease pests and their associated damage on your farm. Know the biology and ecology of key pests in your planting. Know how climate and location influence pest infestation in your field. Learn to differentiate between beneficial organisms and pests. Assess the potential of beneficials to control pests. Find accurate information on appropriate pest control options, their use, efficacy, and potential adverse effects. Most of the skills listed above can be acquired through training, short-courses, or from appropriate and relevant publications such as field guides and IPM manuals. Cultural Practices Cultural practices form the foundation of a good IPM program that reduce pest populations and minimize diseases. By choosing the right site to grow strawberries, you can lower disease and insect pest pressure. Strawberries should be planted in well-drained soil that does not have standing water following a heavy summer rainstorm. Planting on higher ground minimizes frost damage, while increasing air circulation around the strawberry plants. Good air circulation allows the berries to dry out faster, reducing gray mold and anthracnose outbreaks. Strawberries should be rotated to different fields at regular intervals. Land that has been in strawberries for four years should be planted to another crop or a series of cover crops for one to two years to reduce root diseases. Solanaceous crops like tomatoes, potatoes and peppers carry verticillium wilt and should be avoided as rotation crops. By rotating crops, growers can reduce the number of weeds and weed seeds in a field. Perennial weeds like quackgrass, white clover and Canada thistle expand through existing fields. Fields with quackgrass, white clover or Canada thistle should be plowed and replaced with a cover crop. Slow moving pests like strawberry bud weevil and cyclamen mites build up gradually each year, and many strawberry growers have eliminated sprays for both pests by plowing their strawberry fields under after one or two harvest seasons (Chapter 8). Straw mulch can reduce fruit diseases better than fungicides. Straw mulch reduces winter injury, and plants that have less winter injury have fewer diseases. Straw mulch is equally important in the spring and summer, when it reduces fruit diseases by keeping fungi from moving from the soil or dead leaves to the strawberry fruit. When possible, chop the straw when applying straw in the fall. Many people use straw choppers developed specifically for strawberries, but straw choppers developed for animal bedding or road construction work well too. Finely chopped straw falls between the plants and protects the developing fruit better than unchopped straw. When removing straw in spring, ½ to 1 of straw should be left over the row to keep fruit off the soil. 7

8 Most strawberry growers renovate their fields after harvest, which helps control many diseases and insect pests. During renovation, growers mow the leaves off the strawberry plants and till between the rows, narrowing the rows to a specified width. Mowing interrupts the disease cycle of leaf diseases, resulting in healthier leaves during late summer. Mowing should be done before August 1, so that plants can develop a new canopy by the middle of August. Growers who remove mowed leaves during renovation have found fewer leaf diseases. Mowing reduces the number of plants in the rows and improves air circulation. Rows should be narrowed to 12 to 20 at the end of the growing season. Narrow rows dry faster and expose the fruit to more sun, thereby reducing the chance for fungi to infect fruit. Resistant Varieties Plant breeders have enhanced disease resistance to leaf spot, red stele (rare in Minnesota) and verticillium wilt. Many popular varieties in Minnesota are resistant to diseases and insect pests. Honeoye shows some resistance to tarnished plant bug. Glooscap, Cavendish, Annapolis and Honeoye rarely get leaf spot or leaf scorch above economic thresholds. New strawberry varieties are being introduced faster than scientists can evaluate their resistance to secondary diseases and pests, and new pests and diseases are constantly moving into Minnesota. Strawberry growers are finding that some varieties are more resistant to the new diseases than others. Before planting, always talk to other strawberry growers in your area to determine which varieties are most resistant to diseases. Economic/Action Thresholds In conventional pest control, growers tried to eradicate pests. In IPM, growers try to manage pests and keep their populations below a level that will cause economic damage. The term economic threshold refers to the point when the economic losses caused by a pest exceed the cost of the pesticide application. In most cases, the insect pests must be controlled long before any damage is seen, and growers must follow thresholds that have been experimentally determined by scientists. By spraying at economic thresholds, growers can save money, reduce pesticide use and achieve better pest control. The published thresholds serve as mere guidelines or recommendations for making treatment decisions. Growers are encouraged to use these guidelines in combination with past experience and the history of their strawberry plantings to make treatment decisions. Pesticide Resistance Growers, who use the same pesticide over and over for a decade or longer, notice that the pesticide begins to lose its effectiveness. Pests that survive the sprays reproduce and pass genes with resistance to the pesticide on to the next generation. After a while resistant pests multiply. Growers must either increase the rates of the pesticide or change pesticides. Scientists have documented pesticide resistance in all types of pests, including weeds, insects, fungi, bacteria and mites. Many new fungicides and insecticides are highly effective and cause little environment damage, but fungi and insects will develop resistance to the new products if steps are not taken to slow resistance. Pesticide resistance develops slower when growers rely on alternative methods of control such as cultural practices and resistant varieties. Pests that move between strawberry fields and other host plants, such as tarnished plant bug, are less likely to develop pesticide resistance than pests that primarily live in strawberry plants, like cyclamen mites. 8 Growers should alternate one pesticide with another pesticide with a different mode of action to slow the development of pesticide resistance. The alternate pesticides should have different modes of action. For example, two sprays for controlling anthracnose in strawberries, Cabrio and Quadris, have identical modes of action, and the anthracnose fungi will develop resistance to both fungicides if the two fungicides are alternated. Many pesticides with the same active ingredient and mode of action are marketed by different manufacturers under different trade names, so growers should know the name of the active ingredients of pesticides they are spraying. Table 1 groups fungicides with different modes of action.

9 A group of scientists have classified fungicides into 43 specific groups or codes based on their mode of action. Only a few of those groups have fungicides labeled for strawberry producers (Table 1). In addition, there are several fungicides that have multiple modes of action (multi-site fungicides). Fungicides with the same numbered code cannot be alternated, or the fungi can develop resistance to both fungicides. Fungal diseases cannot develop resistance to multi-site fungicides like Captan. Mixing a single site fungicide like Topsin M with Captan will reduce the chance of resistance developing to Topsin M. Table 1. Strawberry Fungicides Grouped by Code for Resistance Development. Never spray fungicides from the same code two times in a row. Information from the Fungicide Resistance and Action Committee (FRAC, Code Group Name Common Name Brand Names 1 Benzimidazols Thiophanate Methyl Topsin M 7 Carboxamides Boscalid Pristine 9 Anilino-Pyrimidines Cyprodinil Switch 11 Strobilurins Azoxystrobin, Pyraclostrobin 12 Phenyl Pyrroles Fudioxonil Switch 17 Hydroxyanalides fenhexamide Elevate Quadris (Abound), Cabrio, Pristine Degree Days and Insect Pest Forecasting In conventional fruit production, most growers used a calendar or a phenological schedule to time pest control in their plantings. With the calendar method, growers sprayed on a weekly schedule without monitoring fruit or pest development. With the phenological schedule, growers sprayed according to the developmental stage of the plant, such as 10% bloom or green fruit. The calendar method is grossly inaccurate, since insect and strawberry development occurs at different calendar dates each year. The phenological method is more accurate, but insects, weeds and fungi have different optimum temperatures for growth than strawberry plants and peak at different stages of crop development each year. Insect life cycles are primarily regulated by temperature. The date that insects emerge each spring depends on factors such as soil temperature, daily highs and overnight lows. The most accurate way to track insect pest maturity and predict when specific pests are most likely to cause economic losses is by calculating degree days. Degree days are a measurement of the cumulative heat for the growing season. Growers can calculate degree days by obtaining the high and low temperature from local climate websites (www. climate.umn.edu), by high/low thermometers at their own farms or by using computerized weather stations. In order to calculate degree-day (DD) accumulations, take the day s maximum temperature (Tmax) and add the day s minimum temperature (Tmin), then divide the result by two and subtract the base temperature. The base temperature is the lowest temperature the insect remains active and varies according to pest. An insect active at cool temperatures will have a lower base temperature than one that needs heat to grow and reproduce. Tarnished plant bugs emerge as soon as the ground thaws and have a base temperature of 50ºF. Clipper weevils emerge later and have a base temperature of 55ºF. To calculate degree days, use the formula: DD = (Tmax + Tmin)/2 - base temperature. The first part of the formula, (Tmax + Tmin)/2, gives an estimate of the average temperature for the day. The second part of the formula subtracts the base temperature specific to the pest. 9

10 Example: The lowest and highest temperatures recorded at a farm were 50ºF and 80ºF. The DD accumulation for that day, with a base 50ºF is: DD = ( ) 2 ) - 50 = = 15 DD This calculation should be done every day, and the degree day totals of each day added together. Figure 1. Weather data logger. A portable weather data logger, such as the one manufactured by Spectrum Technologies Inc. (Fig. 1) automatically calculates accumulated degree-days. This logger has the ability to collect site-specific weather data, including temperature and leaf wetness. The equipment has a long-life battery and can be placed in the field on a stand. Data accumulated by the logger can be downloaded once or twice per week directly to a computer hard drive. A computer software program automatically calculates degree days and can forecast diseases. Forecasting Disease Infection Periods Fungi and bacteria only infect plants when certain temperature and moisture conditions are present. Weather stations such as the instruments shown in Figure 1, tell growers when weather conditions are right for major diseases to develop. Each disease has a specific optimum temperature for infection. For example, botrytis fungi can only infect strawberry flowers if the leaves are wet for 12 hours and the temperature is 70ºF. If weather conditions are not met, the disease will not develop, even if the fungi are present. If the temperature is 50ºF, botrytis fungi do not infect strawberry flowers, even if the leaves are wet for two days. Leaf wetness can be measured with special instruments that are about the size of a thick playing card and attached to dataloggers that record data every ten or fifteen minutes. Leaf wetness monitors record wetness from dew and rain. Dataloggers also record temperature at the same time as leaf wetness. More expensive dataloggers record humidity and rainfall in addition to leaf wetness and temperature. When the data is downloaded into a computer, special programs on the computer tell the grower if an infection period has occurred. Currently, the only disease model available for strawberry growers is for gray mold or botrytis. Even without the disease models, weather stations can guide growers who want to time fungicide sprays. Weather conditions for each major disease are found in the section on specific diseases and pests. 10

11 Forecasting Weed Emergence The date that weeds emerge in the spring is regulated by a combination of soil moisture and temperature. Each species of weed has a different optimum temperature for germination. For example, wild buckwheat can sprout when soil temperatures are 45ºF, and the first wild buckwheat seedlings can be seen shortly after straw is removed from the field. Redroot pigweed seedlings look similar to wild buckwheat, but can only germinate in warm soils. In Minnesota, growers don t see pigweed in their fields until June, when the wild buckwheat is already 2 long. Computer models have been developed for weed emergence which use soil moisture and temperature to predict weed emergence ( Growers should know the worst weeds in their fields, so that they can time their weed control around those weeds. If a new field has wild buckwheat seedlings, a grower can let the buckwheat germinate in early spring, then till the soil before planting in early May. If a field is full of pigweed seeds, the weeds will not germinate until long after an early May planting. Some weeds are also affected by daylength in addition to moisture and temperature. The best time to kill Canada thistles by tillage or herbicides is when they start to form flower buds. Bloom in Canada thistles is triggered by photoperiod, or daylength, so they bloom at almost the same time every year, which is about June 20, in Morris, Minnesota. Pigweed is also affected by daylength. Pigweed that grow in early June grow 3 tall before starting to set seeds, but pigweed that germinate in late August rarely grow more than 6 tall. Late season pigweed rarely causes crop losses in berry fields, but they can still add to the seedbank. 11

12 3. Using Pesticides Safely PESTICIDES are categorized as either restricted use or non-restricted use. A pesticide is classified as restricted use if it meets certain toxicity or environmental impact criteria. Growers who use restricted use pesticides must obtain a pesticide applicator s license or private pesticide applicator certification by passing a test and submitting a completed application form and fee. Most berry growers do not have a license/certification because most pesticides used in strawberry production are not restricted use pesticides. All growers who spray pesticides must observe: 1) The re-entry interval (REI) - the minimum number of days (or hours) before an orchard or property can be re-entered after a pesticide application. 2) The Pre-harvest Interval the minimum number of days required between final spray and harvest. Nearly all strawberry growers must comply with worker protection standards (WPS) to protect agricultural workers. The WPS is in effect when workers enter a field within thirty days after spraying, so most berry growers must comply with some part of the WPS. There are, however, different rules depending on the type of employee hired. Agriculture Owners: If the only people working on your farm are yourself and your immediate family, you must comply with the following rules: 1) Use proper personal protective equipment (PPE) such as gloves, eyewear, clothes, or aprons when mixing or applying pesticides; (the required PPE for each pesticide is found on the pesticide label). 2) Apply pesticides in a manner so as not to contact workers or other persons either directly or through drift. 3) Keep family members out of areas being treated with pesticides. 4) Keep records of all Restricted Use Pesticide applications. (This is not a requirement of the WPS, but it is still the law). It is also recommended that you keep records of any pesticide applications you make. Employers: Employers who hire workers outside the family and within thirty days of a pesticide application with a REI, must comply with all WPS requirements. Employees can be classified as either workers or handlers. Workers work with plants and do tasks such as watering, weeding, and harvesting. Handlers work with pesticides and do tasks such as: a) Mix, load, transfer, or apply pesticides. b) Handle opened pesticide containers. c) Act as flaggers. d) Clean, handle, adjust or repair the parts of equipment that may contain pesticide residues. e) Assist with pesticide applications. Handlers require more extensive training than workers. 12

13 All employers must do the following in order to comply with the WPS, regardless of whether they hire handlers or workers: 1) Display the following information at a central location. a. Maintain a 30-day pesticide application record. The record should include the location of the field sprayed, product name, EPA registration number, date and time the pesticide was applied and the restricted-entry interval of the pesticide. b. Emergency medical information, which includes the name, telephone number and address of the nearest emergency medical facility. c. An EPA approved pesticide safety poster. 2) Provide WPS pesticide safety training for new employees. a. Workers must be trained within five days of employment. b. Handlers must be trained immediately. (Minnesota Licensed pesticide applicators are exempt from the training requirement.) c. Workers and handlers must be provided safety training once every five years. 3) Have a decontamination site that contains: a. Water for routine washing and emergency eyeflush. i. Recommended - one gallon per worker. ii. Recommended - three gallons per handler. b. Soap and single use towels. c. Decontaminations sites should be located within ¼ mile of where employees are working. 4) Provide emergency assistance to any worker or handler who has been injured or poisoned by a pesticide as a result of that employment. Specific for pesticide handlers: a. Have pesticide labels and Material Safety Data Sheet (MSDS) available for handlers to review. b. Provide decontamination supplies at the pesticide mixing and loading area. c. Include an emergency change of clothing (example: coveralls) at all handler decontamination sites. d. Provide at least one pint of emergency eye flush when the pesticide label requires that protective eyewear be worn. e. Provide all required PPE for pesticide handler when mixing, loading, applying pesticides or conducting other handler tasks. f. Provide an area separate from pesticide storage or mixing area for handlers to change and store clothing. Warning Signs All workers need to be notified when a field is to be sprayed, either verbally or by posting the area with EPA approved warning signs. If you spray in the evening with a pesticide that has a 12 hour or less REI, employees do not need to be notified if the REI will have expired by the time the employees return. Spills All pesticide spills must be reported to the Minnesota Department of Agriculture by calling the Minnesota Duty Officer (MDO) at The MDA provides a 24 hour/7 day a week point of contact service for reporting spills. The MDO will forward your call to staff who will provide you with cleanup and disposal guidance. Personal Protective Equipment When mixing pesticides the applicator should use the appropriate clothing and equipment, which is usually listed on the front page of the pesticide label. 13

14 4. Pest Scouting PEST SCOUTING enables a grower to determine if pest numbers are large enough to require treatment and to time sprays that coincide with the most susceptible stage of the pest. Scouting usually involves checking for eggs, larvae or adults of a given pest in berry leaves, fruits, or flowers. Most pests can be seen with the naked eye, but for small specimens such as mites and insect eggs, a hand lens may be needed. Aphids, plant bugs, thrips, and populations of natural enemies are commonly sampled with beating-trays. Knowing how to correctly identify pests at all life stages is critical, and growers should be able to distinguish pests from closely related or look-alike species. For this purpose, growers are encouraged to use this manual hand-in-hand with the Field Guide for Identifi cation of Pest Insects, Diseases, and Benefi cial Organisms in Minnesota Strawberry Fields. Growers need to record weekly or daily pest scouting data for proper and timely decision-making. Accurate records include a map of all the fields, a list of insect pests found in those fields, the numbers of insects recorded on each sampling date and control measures taken on those fields. In Minnesota, scouting should begin in early spring and continue until strawberry renovation. Pest Scouting Equipment The following equipment and tools are necessary for pest scouting: Notebook (or clipboard with data sheet) for record-keeping. Hand lens (10X or stronger), for small insects, eggs, and mites. Sweep net to scout ground cover or capture flying insects. Beating-tray (preferably white in color) to scout pests and beneficials on the fruit and foliage. A copy of the Field Guide for Identifi cation of Pest Insects, Diseases, and Benefi cial Organisms in Minnesota Strawberry Fields. Alcohol vials, plastic bags, and capsules for insect collection. Scouting Techniques Different scouting techniques are available and can be used depending on the pest or pest stage being scouted. The following are suggested as general guidelines for scouting: Divide a large planting into blocks of 1-2 acres of similar age, variety, and soil type. Major pests like tarnished plant bug should be scouted at least twice a week. Leaf pests can be monitored once a week. To scout plants within a block, make a random selection based on a pre-determined selection pattern (e.g. diagonal, V-shaped pattern, etc). Figure 2. Hand lens Figure 3. Sweep net Figure 4. Beating-tray 14

15 5. Strawberry Developmental Stages and Associated Pests - Planting Year Plant Stage Pests Damage Planting to First Runners White Grubs Soil Insect Eats roots and kills plants Potato Leafhopper Leaf Insect Causes yellow leaves Root Weevils Soil Insect - Stunt plants Black Root Rot Root Disease Stunts plants Deer Defoliate plants Verticillium Wilt Soil Disease Kills plants First Daughter Plants to Full Canopy White Grubs Black Root Rot Powdery Mildew Leaf Spot Deer Soil Insect Kills plants Root Disease Stunts plants Leaf Disease Sunts plants Leaf Disease Stunts plants Defoliate and stunt plants Full Canopy to Dormancy Powdery Mildew Leaf Disease Twospotted Spider Mites Leaf Feeder Stunts plants Deer Stunts or kills plants Strawberry Developmental Stages and Associated Pests Bearing Fields Plant Stage Early Spring Pre-bloom Full Bloom Green Fruit Ripe Fruit Post-harvest Pests of Concern Deer Cyclamen Mite Strawberry Bud Weevil Tarnished Plant Bug Leafrollers Botrytis Thrips Strawberry Root Aphid Tarnished Plant Bugs Botrytis Leaf Spot Thrips Meadow Spittlebug Botrytis Leather Rot Slugs Meadow Spittlebug Sap Beetles Anthracnose Leather Rot Potato Leafhopper Powdery Mildew Leaf Spot Leaf Scorch Anthracnose Black Root Rot Cyclamen Mites Deer 15

16 6. Biology and Management of Select Insect Pests and Diseases of Strawberry JUNE-BEARING strawberries are a good crop for Minnesota, with its warm summers, large cities and vacation areas. However, not only do people like strawberries, but many pests like to eat them as well. Some insects eat the seeds while others prefer fruit. In order to protect their crop from the many pests, strawberry growers should learn how to identify and control the major pests. By using an integrated approach, berry growers can save money while achieving better pest control and producing more berries. In this section, the biology, ecology, monitoring and management strategies for key pests of strawberry in Minnesota are discussed so that growers can learn to identify the pests on their farms and develop management plans for each pest. A detailed description and identification of each pest as well as other strawberry pests is provided in the Field Guide for Identifi cation of Pest Insects, Diseases, and Beneficial Organisms in Minnesota Strawberry Fields. For each pest, we describe available pest management strategies, and the Minnesota Department of Agriculture does not endorse particular products. We have attempted to leave out specific pesticide information or recommendations in this chapter. Information on pesticide options is given in the Appendices. INSECTS Tarnished Plant Bug (Lygus lineolaris) Tarnished plant bug (TPB) has one of the broadest host ranges of any major insect pest, feeding on alfalfa and grasses in addition to strawberry blossoms. Biology TPB live in the tall grasses and plants in alfalfa fields and pastures, and they avoid forests and fields with shortly mown grass. TPB overwinter as adults in vegetation and plant debris and emerge in the spring when temperatures reach and remain around 50 F (early April). Emerging adults feed upon actively growing plant tissue such as leaves, stems, and flower buds. When strawberries bloom, TPB adults can fly over 50 yards looking for flowers. Females mate and insert their eggs in blossoms in April and early May. Nymphs emerge 7-10 days later (early-mid May) and feed upon the developing tissue. There are several generations each year, so adults and nymphs can be found from April or May until a heavy frost in the fall. Damage Tarnished plant bugs eat parts of the blossom by piercing and sucking out plant juices with their beak-like mouthparts. TPB kill developing seeds, which prevents the fruit tissue from expanding, leading to small seedy strawberries with a woody texture called button berry, or cat-faced berry. Moderate damage is unnoticeable, but severely damaged fruits are unmarketable (Fig. 5). Lower yields are due to a combination of smaller and unmarketable fruit. Nymphs appear to cause most of the damage during bloom. Growers who time their control to small nymphs in the first or second instar have achieved good control. If a field has a high population of fourth and fifth instar nymphs, some of the crop has already been lost. 16

17 Figure 5. Different levels of TPB damage in strawberry. The fi eld was sprayed after TPB damaged the king bloom (center). The secondary fruit (top left) had minor, but marketable damage. The tertiary fruit (white) have almost no damage. Without spray, the damage would have been least in the fi rst fruit and worst in the last fruit. Monitoring TPB monitoring should start in early April to detect migrating adults and continue until harvest. Both adults and nymphs can be monitored, but thresholds for nymphs are better understood than adults. TPB should be monitored every two days before and during bloom if a grower is considering reducing pesticide applications. Adults: Adult TPB can be monitored by walking the fields and looking for bugs that are feeding on strawberry flowers or flying above the strawberry canopy. There is currently no suggested threshold for adults. If adults are seen at bloom, the threshold for nymphs can be lowered to less than 1 nymph per four clusters. Nymphs: Begin sampling for nymphs at 5% bloom. Nymphs should be monitored at least every two days if a grower wants to reduce sprays. Walking through a field in a V-shaped sampling pattern, tap blossom clusters against a white pan and look for small, green nymphs that move rapidly across the pan. Sample at least 20 blossom clusters per field. The suggested action threshold is 1 out of 4 blossom clusters infested with one or more TPB nymphs. If nymphs are very small, a lower threshold can be used. Control Roughly 20% of all Minnesota strawberry farms have TPB under threshold numbers each spring and do not need insecticides. Growers interested in reducing or skipping sprays should be educated in by a professional on how to identify all stages of the TPB. Biological and Cultural Control: Innundative releases of the parasitic wasps, Anaphes iole and Peristenus digoneutis have been effective in California and New England. Row covers can cause strawberries to bloom before the TPB adults emerge. Weed control in the berry field is important because weeds may attract TPB into the strawberry planting and allow adults to overwinter in the strawberry field. Grass driveways and parking lots should be mown on a weekly basis so that the lawn does not become TPB habitat. Avoid mowing nearby hayfields when berries are blooming. Mowing will drive the adult TPB from the hayfields into strawberry plantings. As a rule, TPB prefer blooming alfalfa to strawberries, and they will not fly from a blooming alfalfa field to a strawberry field unless the field is mown. Although no strawberry variety is known to be resistant to TPB, Honeoye is less susceptible to feeding injury than other varieties. Avoid planting day neutral varieties (Chapter 9). TPB levels sharply rise throughout the summer. Varieties that bloom in July or August are especially vulnerable to injury. Chemical Control: TPB can be killed with soft and organically approved insecticides. Insecticide rates and options are mentioned in Appendix 4. Sprays applied just before bloom kill overwintered adults and do not harm bees and other pollinators. 17

18 Strawberry Bud Weevil (Anthonomous signatus) Strawberry bud weevil or clipper weevil (SBW) reduces the number of blossoms in the field. Clipper weevils are rare in the southern three tiers of counties in Minnesota, but in the rest of Minnesota, they can cause large economic losses in fields in their second or third year of picking. Biology SBW overwinter as adult weevils in fence-rows, wooded areas, and berry fields. Once temperatures reach 60 F, females search for flower buds where they can lay their eggs. Adults have chewing mouthparts at the end of a long snout. Adults feed on petals, pollen and the developing flower receptacle. The females deposit eggs in the buds (Fig. 6). After depositing the egg, the female SBW girdles the bud and clips the stem, causing the bud to hang down or fall to the ground. Egg laying usually peaks in early bloom (approximately 300 DD base 50 F). A week later, the egg hatches into a white, legless grub. The larva develops inside the bud, reaching maturity in 3-4 weeks. Larvae exit the buds and pupate in the soil, emerging as adults in late June through July. After feeding on the pollen from various flowers for a short time, the new adults seek hibernating sites and remain until the next spring. Only one generation of clipper occurs per year in Minnesota. Clipper weevils rarely fly or walk more than 30 while looking for food or places to lay eggs. Damage When the female clips the bud, the fruit is lost. In severe infestations, 75% of the buds are killed. If the weevils emerge early, the majority of the clipped buds will be king bloom, which typically produce the largest fruit. Injury is most common along edges of fields near woodlots. Monitoring Clipper weevils are difficult to see because they are small and hide in the strawberry canopy. Most people monitor clipped buds or damaged flowers. Monitoring should begin just before bloom. Clipper weevils are unevenly distributed across fields, with some sections having severe damage and others having no weevils. Following a V-shaped sampling pattern, walk across the field. If the plants are not in bloom, look for clipped buds. If plants are blooming, look for holes in the petals (Fig. 7). If you find flowers with holes in the petals, check for clipped buds. If weevils are actively feeding on flower petals and laying eggs, the treatment threshold is 1 clipped bud per 2 of row. If clippers are finishing laying eggs, and have stopped feeding a higher threshold of 6 clipped buds per 3 of row can be used. Cultural and Biological Control: Clipper weevils in strawberry fields in their first year of picking are usually below economic thresholds, and therefore do not need to be sprayed. Immediately plowing under old beds following harvest and removal of leaves and mulch may help by reducing the overwintering habitat of the weevil. Regularly rotate fields out of production so that there are few fields in production for more than three picking seasons. 18 Chemical Control: Insecticides labeled for SBW tend to be harsh, with long pre-harvest intervals. Rates are higher than required for TPB. In fields with a history of clipper damage, growers can use a preventative spray prior to bloom, after buds have emerged from the crown and when temperatures have reached 65ºF. Insecticide options are mentioned in Appendix 4. Complete field treatment is recommended for older plantings with a history of high SBW pressure.

19 Flower Thrips (Frankliniella tritici) Flower thrips are extremely small insects that damage strawberry fields once every three or four years. Although thrip damage is rare, when it does occur, entire fields can be unmarketable. Biology Flower thrips winter in the southern region of the United States and are carried northward on frontal systems in early summer. Female thrips lay their eggs under the surface of leaves. Eggs hatch in about 2-4 days. There are two larval instars. Development from egg to adult can be completed within a week or two during hot weather. Because of this short generation cycle, the thrips can increase rapidly during hot spells. Damage Thrips have rasping, sucking mouthparts that cut the skin cells of strawberry fruit, causing the fruit to turn bronze colored or to cause a slight russetting. The skin cannot properly stretch as it ripens, and the seeds stick out of the skin. In some cases, large numbers of thrips have been counted in fields, with little or no damaged fruit. In other cases, fields have been ruined when small numbers of insects were counted. Severe thrip damage may be caused by a combination of insects and high temperatures in late bloom. Monitoring Thrips can be monitored at the same time as tarnished plant bug nymphs. When tapping blossom clusters for tarnished plant bug nymphs, always count thrips. Thrips are very small insects, about the size and shape of the strawberry stamens that fall off blossoms in late bloom. The most accurate method of monitoring is outlined below. Collect ten flower buds from a field (use a V-shaped sampling pattern to determine sampling locations). Place the flower buds in a clear plastic ziplock bag, close and put the bag in a hot place for a few minutes to kill the thrips. Due to their small size, it may be useful to use a hand lens to identify thrips. The popular threshold is more than 10 thrips per flower bud. Biological and Cultural Control: During the 2006 growing season, strawberry growers noticed large differences in damage severity between cultivars. Jewel and Glooscap were damaged, but had normal tasting fruit. Cavendish and Honeoye in the same fields had a bitter taste and were unmarketable. Naturally occurring minute pirate bugs (Orius spp.) feed on thrips. Orius are also available commercially and have proven successful in greenhouses. Chemical Control: In general, treatments applied to control TPB will offer some protection against thrips, although Endosulfan is only moderately effective against thrips. Sprays targeted against thrips may disrupt biological control of other pests such as the twospotted spider mite. Consider treating only if populations reach over 10 thrips per blossom cluster. If hot weather is predicted, use a lower threshold. 19

20 Twospotted Spider Mite (Tetranychus urticae) Twospotted spider mite (TSSM) feeds on the leaves of many fruit crops. TSSM is more common in states south of Minnesota, but during hot, dry summers the mites can build up in local fields. Biology Adult spider mites feed and deposit eggs on the underside of the leaf starting in early spring. In a heavy infestation, a tangle of fine, silken threads can be found on the leaves. TSSM mature two weeks after hatching, and new broods are produced continuously from early spring to late fall. Mite populations increase rapidly in hot, dry weather. Spider mites disperse into plantings on the silken threads in the wind. TSSM overwinter as mature fertile females in protected areas in the fields. Damage Mites have piercing, sucking mouthparts. They feed by sucking the chlorophyll from leaf cells, causing the characteristic whitish spotting, eventually turning the leaves a coppery-bronze color. TSSM damage usually occurs during hot, dry weather, and is first noticed in areas of the field that are dry. Heavily infested plants are stunted. Monitoring Plants with bronzed, dusty leaves should be inspected for TSSM. Using a hand lens, inspect the underside of leaflets for TSSM and the quicker predatory mites, which are either clear or orange in color. An acceptable threshold is 5 mites per leaflet. Biological and Cultural Control: Plants that are healthy and properly watered are more likely to fight off mite infestations than sick, poorly watered plants. In healthy fields, mites are kept under control by predatory mites, such as Amblyseius fallacis. Pyrethroids and several broad spectrum insecticides, such as Sevin can kill predators and cause spider mite populations to flare up. Predatory mites can be introduced to fields when damage is starting to show on the plants. Avoid using broad spectrum insecticides that kill predatory mites. 20

21 Cyclamen Mite (Steneotarsonemus pallidus) Cyclamen mites are significantly smaller than spider mites, but are more common, infecting roughly 20% of the strawberry fields in Minnesota. Cyclamen mites have few other hosts than strawberry plants. Biology Cyclamen mites live in the crown of the plants and feed on developing leaves by piercing and sucking nutrients from the leaves. As the leaf unfolds, the mites move onto smaller leaves in the center of the plant. Cyclamen mites overwinter in the strawberry crown and start to feed as soon as the plant begins to grow in early spring. Cyclamen mites multiply rapidly in hot weather. Damage Cyclamen mite damage can be seen as leaves unfold. Damaged leaves are small, crinkled, twisted and a yellow color. In early stages of an infestation, older leaves are healthy while the young leaves in the center are small and crinkled. In older infestations, the canopy is 25-50% smaller than surrounding uninfested plants. During spring, cyclamen mites feed on flowers, producing symptoms similar to thrips. Often the damage is not seen until the end of picking, when they spread during hot weather. Management Monitoring: Plants showing symptoms of cyclamen mite should be carefully inspected in order to assure the grower that the mites are causing the observed damage. Nutrient deficiencies and diseases can cause similar symptoms. Collect leaves from the center of the crown, less than 1 in diameter Place leaves under a dissecting microscope or inspect with a hand lens. Cyclamen mites are much smaller than TSSM and difficult to see even with a good microscope. Mature mites are pinkish-red, while immature mites are a translucent white. If plants show cyclamen mite symptoms and if mites are observed, take control measures. Cultural Control: Cyclamen mites usually come into fields through nursery planting stock. Always buy certified, disease-free plants. If a few plants show signs of cyclamen mites the first year, remove plants from fields Cyclamen mites almost never damage fields until after their first year of production. If fields are only picked one year, cyclamen mites remain below threshold. Certain varieties, such as Cavendish and Annapolis appear to be very susceptible. Jewel is most tolerant. Chemical control: Because cyclamen mites live in the center of the crown, they are protected from insecticides by the leaf canopy. Insecticides should only be sprayed when there are few or no leaves, either after renovation or in early spring, as the first buds are emerging from the crown. Spray volume should be at least 200 gallons per acre to make sure the insecticides penetrate the crown. Cyclamen mite infestations are usually limited to small sections of each field and many growers only need to spot spray infested areas. 21

22 Slugs Slugs are wormlike relatives of the snails. Minnesota slugs range from a ¼ to 1½. They have no shell, so their main protection is a layer of slime. When they move, they leave a familiar trail of slime. Slugs rarely move more than a few feet in their lifetime. Biology Because slugs are only protected by a layer of slime, they have two basic requirements in order to thrive: humidity and dead vegetation. The straw in an irrigated strawberry field is ideal slug habitat. Most slugs overwinter as egg masses. Although some adult slugs overwinter, the greatest damage appears to be caused by slugs that hatch each spring. Damage On humid nights, slugs leave their protective habitat in the straw and go looking for food above ground. Slugs make small holes on the surface of ripe strawberries. Sometimes the damage is so light that most customers don t notice. Other times the slugs will burrow a hole or take shelter beneath a cap to surprise customers. In severe infestations, slug damage can cause major economic losses. Management Monitoring: Slugs should be monitored during and after bloom. Look for slime trails on irrigation pipe or other structures in the fields. Slugs can also be monitored by placing wooden boards in the straw in the strawberry fields. Slugs congregate under the boards during the day. Periodically, pick up the boards to see if the slug population is increasing. Cultural Control Cultural control in strawberries is always difficult, because the straw provides such an ideal habitat for slugs. Tilling straw under at renovation and later in the fall will disrupt the slug s lifecycle and reduce the number of surviving slugs in the field. Chemical Control: Insecticides do not control slugs, because they are not insects, and they hide in the straw. The most common way to kill slugs is to bait them with a sugar-pesticide mix. Always apply slug bait before berries ripen. Slugs prefer ripe berries to slug bait. Sprinkle baits in areas that snails and slugs regularly frequent such as areas around sprinkler heads. Placing baits repeatedly in the same areas maximizes control because they tend to return to food source sites. Most baits are a mixture of metaldehyde and sugar, which are also poisonous to pets. Iron phosphate baits are less effective, but cleared for organic production and safe around children and pets. Baits break down after rains or irrigation. 22

23 White Grubs White grubs are the larvae of the June beetle, Phyllophaga anxia or P. implicata. Biology June beetles live for three years, and are grubs for all but two months of their life cycle. Adult beetles emerge in late May or early June and feed on tree leaves. After mating, the females lay their eggs in the soil. Grubs hatch in late July, and primarily feed on fine plant roots. In September, the grubs burrow deep in the soil and hibernate below the frost line. The following June, second year grubs reach the surface and eat roots until they hibernate in September. Third year grubs only feed for one or two months before burrowing below the frost line and pupating. During the third winter, the grubs metamorphose into beetles. Damage Grubs eat strawberry roots, causing the plants to suddenly die (Fig. 8). Damage is most common in the first months after planting. First year grubs eat the fine roots and leave the fibrous roots. Second and third year grubs eat roots to within 1 of the crown. Grubs can follow strawberry rows, killing every plant they find. Figure 8. Grub-killed plant. Management Monitoring: When a plant wilts and dies, always pull the plant. If the plant has no roots, there are grubs in the field. If the plant has a full set of roots, the culprit is most likely diseases. Look for grubs on dying plants, not dead plants. Count the number of grubs per plant and the number of infected plants per field. Cultural Control: Tilling fallow fields can kill some grubs, but most grubs immediately burrow back into the soil. Tilling can be more efficient if a flock of seagulls or other birds follow the tractor and eat grubs. Skunks will eat all the grubs in a field, but also damage plants. In infested strawberry fields, the easiest way to kill grubs is to dig plants, kill the grubs and place the plant back in the soil. Grubs are rare near dead plants, because the grubs have already moved to the next healthy plant. Chemical Control: If there are two or three grubs per plant, an insecticide spray may be necessary. Insecticides are moderately effective, because insecticides must move through the soil to reach the grubs. Grub insecticides are extremely toxic and kill earthworms. 23

24 DISEASES Gray Mold (Botrytis cinerea) The botrytis fungus that causes gray mold is found in low levels in all strawberry fields. When Minnesota strawberry growers began adopting the narrow matted row system in the 1990 s, gray mold declined. Gray mold can still ruin an entire crop during moist weather and limited air movement. Infection is most severe in the center of the rows. Biology Botrytis cinerea spends most of its life cycle living harmlessly in strawberry leaves. The pathogen overwinters in dead and living leaves. Disease Development Botrytis infects the flowers during bloom, but normally, the disease is not seen until the berries ripen, or even after the berries are harvested. Primary infections occur when spores move from dead or dying leaves by wind and rain to the flowers. Once on the flowers, spores only germinate if the flower is wet for over 14 hours and the temperature is at F. Spores germinate and grow into healthy pistils or stamens. In most cases, the infection remains latent until the fruit matures. As the fruit ripens, it grows through and rots the fruit. The gray or white fuzz on the surface of the fruit are spores that cause secondary infections on surrounding healthy fruit both before and after harvest. The disease can turn a carton of firm red berries into a smelly gray mass in less than 24 hours. Management The primary time to control gray mold is during bloom. If blossoms are not wet for more than 24 hours from rainfall, irrigation or dew, there will be little or no gray mold. Cultural Control: Do not apply more than 100 pounds actual nitrogen per year, of which 30 pounds or less should be applied before harvest. Excess nitrogen encourages excess leaf growth, which increases humidity around the flowers. When using overhead irrigation, time irrigation so that the foliage does not stay wet for more than 12 hours. Either irrigate in early afternoon so that the foliage dries out before sunset or in early morning when leaves are already wet with dew. Keep rows to 20 or less in the fall so that fruit can quickly dry out after rain or irrigation. Always use enough straw so that the strawberry fruit is sitting on straw and not on soil. Removing overripe fruit may help control secondary infections. Chemical Control: If the weather during bloom is damp and warm, spray fungicides at 10% and 70% bloom. Fungicides must be rotated between classes of fungicides or two classes must be mixed together to avoid resistance building up. Typically, a contact fungicide like captan or thiram is mixed with a systemic fungicide like fenhexamid, cyprodinal or thiophanate. Other fungicide options are discussed in the Appendices. 24

25 Anthracnose (Colletotrichum spp.) Anthracnose first became a problem in Minnesota strawberry fields in the early 1990 s. Anthracnose was primarily considered to be a subtropical disease. Anthracnose does need tropical conditions in order to infect strawberry fruit, but there are enough warm rainstorms in Minnesota during strawberry harvest that anthracnose has become one of the worst strawberry diseases in the state. Biology Anthracnose is usually introduced into strawberry fields through infected planting material. Some fields in Minnesota have no anthracnose, therefore there is no reason to worry about the disease. Unfortunately, we currently lack tests to determine if fields have the disease. Once anthracnose is in a field, the disease overwinters in leaf litter and dead plants. Colletotrichum acutatum lives harmlessly on the surface of leaves. Occasionally, the disease attacks petioles, but typically the disease does not show until the fungus infects the fruit. Disease Development Hard rainfall splashes Colletotrichum spores from the leaves onto the fruit. Fruit infections do not occur unless the temperature is near 70 F. Thunderstorms provide both the heat and hard rainfall to cause infection. (Fig. 9). The disease shows up on the fruit 2-3 days after infection periods. Figure 9. Infection periods for anthracnose. Thunderstorms on July 3 and July 13 had both the high rainfall and the high temperatures to allow Colletotrichum to infect fruit. Management Cultural Control: Plant only certified disease-free nursery stock. Always have a thick layer of straw mulch between and in the rows. Avoid excessive nitrogen fertilizer. Mesabi appears to have some resistance against anthracnose. Chemical Control: Anthracnose should be sprayed with fungicide before the fruit develop the shrunken brown spots. Spraying a field where 30% of the fruit have anthracnose is too late. Currently, two fungicides are labeled for anthracnose. Some gray mold fungicides do not control anthracnose. Fungicide options are discussed in the Appendix 5. Fungicides are most effective if sprayed right before or after a thunderstorm. 25

26 Leather Rot (Phytophthora cactorum) Leather rot is primarily a concern in heavier soils. Strawberry farms on sandy soils in central Minnesota may not have to spray for leather rot. Biology Leather rot is caused by a water mold that lives in most soils. The leather rot organism only infects strawberry fruit if water moves mold spores from the soil to the fruit. Water flowing over a field, standing water, and splashing tractor tires can initiate leather rot infections. Disease Development Leather rot only develops after large rainstorms or excessive irrigation. If infected, the fruit shows symptoms within 24 hours of the rainstorm. Green fruit and flowers shrivel up and die. Ripe fruit may turn brown or may only show a slight pink on one side of the fruit. Once fruit are infected, then the disease can pass from fruit to fruit. All infected ripe fruit, whether brown or light pink, have a distinctive, foul odor. The biggest danger with leather rot is that customers may not recognize the disease and accidentally pick slightly discolored, infected fruit. One infected fruit can make an entire batch of jelly develop a bitter taste. Management Cultural Control: Always plant in well-drained soil. Avoid sites that have standing water following summer rainstorms. If one section of a proposed field has a low spot, plant a perennial cover crop instead of strawberries. Always use straw mulch. Raindrops that strike the soil and splash dirt onto fruit can spread the Phytophthora fungi to the fruit. Leather rot outbreaks are usually limited to small sections of a field. If ripe fruit are infected in a small section of a field, do not allow pickers into the affected area. Chemical Control: Fungicides that control leather rot are expensive and are not totally effective. Synthetic fungicides such as Metalaxyl are systemic and can be sprayed at bloom. Potassium phosphite products have been shown to control leather rot. 26

27 Root Diseases Root diseases cause plants to become stunted. In many cases, the plants will show nutrient deficiencies that fertilization cannot cure. Biology The most common root disease in Minnesota is Black Root Rot (BRR). BRR is caused by a complex of different pathogens, including nematodes, the water mold Pythium, and the fungus Rhizoctonia. Rhizoctonia has been consistently isolated from Minnesota fields with BRR. Fields with BRR have stunted plants that bloom and bear fruit but with small size and low yields. Plants are most likely to die from BRR during late picking. Disease Development The pathogens that cause BRR live in the soil. The disease grows worse each time a field is replanted to strawberries. In fields with BRR, many of the new roots are killed either at the tips of the root, or new roots have small dead spots. BRR slows plant growth, but plants grow and set runners normally. Growers often do not notice the disease, because the only symptoms are small plants. Plants with BRR often die at the end of harvest. Management Cultural Control: The best way to control BRR is through a series of cover crops and short rotations. Certain cover crops, such as marigolds or mustards, kill some of the pathogens. A field with severe BRR should be kept out of strawberries for four years. The fungus Trichoderma appears to kill Rhizoctonia. Trichoderma has been developed into a commercially available fungicide, under several different names. Fields can be inoculated with Trichoderma either at planting or during fallow periods. Since BRR is caused by several pathogens, resistant cultivars vary from site to site. Try several different varieties to see which grow best in a particular site. Chemical Control: Few chemicals have been shown to reduce BRR. 27

28 7. Weed Management in Minnesota Strawberry Fields WEEDING is the highest production cost for Minnesota strawberry growers. In addition to lowering yields, weeds make picking difficult or unpleasant for hired harvesters and pick-your-own customers. Weeds can increase disease pressure by reducing air movement in the plant canopy, as well as provide habitat for tarnish plant bugs. The standard strawberry production system in Minnesota is the matted row, where plants are planted approximately 18 apart, and the rows fill in with runner plants. Once the runner plants become established, weeds can no longer be removed with tillage. There are few herbicides labeled for use in strawberries, and all herbicides have the potential to damage strawberry plants. No herbicide kills or prevents all weeds, and growers inevitably must spend time in the fields with a good hoe and a pair of gloves. Minnesota strawberry growers use a combination of crop rotation, herbicides, hand hoeing, hand weeding, tillage, and mulch to control weeds in their plantings. Weeds often limit the number of years a strawberry field can stay in production. Even with conscientious management, strawberry fields rarely stay sufficiently weed-free for longer than five years. Strawberry fields should be rotated out of strawberries while the weed infestation is relatively minor rather than waiting for yields to decline, which leads to a decline in your customer base because your customers can t find berries among the weeds. Important principles of weed control in strawberry fields are: Plant into a clean, weed-free site. Have adequate labor available to hand-weed both newly planted and bearing fields. Avoid introducing weed seeds into the planting with equipment, straw used for winter mulch, or on wind from nearby weedy areas. Kill and remove weeds that emerge in the field before they set seed. Use herbicides judiciously. Rotate your fields out of strawberries every three years. Every field cannot be producing strawberries all the time! Problem Weeds in Minnesota Strawberry Fields Every strawberry planting will have its own unique suite of weeds, related to previous land use, nearby weed populations, soil type, climate, and management strategies. Most strawberry farmers will recognize the following weeds as troublesome or potentially troublesome species: Perennial Weeds Canada thistle Quackgrass Dandelion Red sorrel (eastern Minnesota) White clover Oxeye daisy Yellow wood sorrel (oxalis) Tree seedlings (box elder, elm, ash) 28

29 Annual Weeds Grains, such as wheat and rye, from straw used for winter mulch Annual grasses: foxtail, pigeon grass, and crabgrass Lambsquarters Redroot pigweed Wild buckwheat or annual bindweed This section outlines weed management strategies for pre-plant site preparation, establishment year, and bearing years. Site Preparation/Rotation Out of Strawberries A site should be free of perennial weeds such as thistle, dandelion, and quackgrass before planting strawberries. Quackgrass, Canada thistle, and white clover cannot be removed from an established strawberry field even with strong herbicides. A prospective field should be tilled or sprayed with a non-residual herbicides such as Glyphosate at least one year before the expected planting date to kill perennial weeds. Cover crops such as annual rye, buckwheat, and sorghum-sudan crowd out perennial weeds and reduce the seed bank of annual weeds. Good weed management on crops like corn or alfalfa will leave the fields clean for strawberry production. Growers who are in a hurry and plant strawberries before they have eliminated weed problems nearly always regret their decision. Weed Control During the Establishment Year Weed control the first three months after planting is critical in order to develop a healthy field that will produce strawberries for three or more years. The most critical time to keep fields free of weeds is the months of June and July (Table 2). Young plants are poor competitors with weeds, and the same irrigation and fertilizer used to help strawberry plants also benefits the weeds. Table 2 summarizes an experiment conducted in New York, where scientists kept newly planted strawberry fields weed free for specific months. The highest yields occurred when fields were kept weed free from June through August. The field that was only weeded in September had almost no yield. Late June and early July are also a time when growers must prepare bearing fields for picking, so every strawberry grower must make time in their schedule to assure that their new fields have few weeds. Table 2. Influence of Weed Control on Yield and Runner Production (Derived from Pritts, 2001). Months Kept Weed Free Yield Runners June - September 3, June - August 3, June and July 2, June 1, No weeding September August - September 1,070 5 July - September 2,

30 Figure 10. First year weed control. In a spot with a low strawberry plant population, the volunteer grain is growing very well. The two most successful strategies growers have for keeping the weeds in new fields under control are preemergent herbicides and cultivation equipment. Existing preemergent herbicides labeled for strawberries can damage strawberry plants and do not kill all weeds. Cultivation equipment such as finger weeders and flex-tine harrows kill weed seedlings without pulling up fresh soil and seeds from deep in the ground. Finger weeders can only be used until the plants start sending out runners, which typically starts in early July. By early July, the first flush of weeds is removed, and weed pressure declines if control was sufficient earlier in the summer. Many strawberry growers apply a preemergence herbicide on first year plants when they start to send out runners. Corn gluten meal or distiller s grain can also be used as a preemergence herbicide while adding nitrogen to the soil, but corn gluten does not prevent weed germination in wet years. Field cultivators with wide shoes can also play an important role in weed control the first growing season. A field cultivator can kill weeds within 2 of the strawberry row until the plant starts sending out runners. When the strawberry plant starts producing runners, the field cultivator pulls runners into straight lines while killing weeds and putting soil over runners. As the strawberry row widens, the operator adjusts the field cultivator to leave a wider section of row undisturbed. Field cultivators kill most weeds in the aisle, so that people who hoe or hand pull weeds only have to concentrate on a narrow section of row. If a new field is kept weed-free for two months, and if the plants send out many runners, the row will have a solid canopy by the middle of August. Once a solid canopy of leaves and plants are established, few weed seedlings can compete with the strawberries. A well established row of strawberries will have few weed problems for most of its productive life. Alternative strategies are being tested by growers and researchers and include the use of mulches in the rows and alleys, cover crops in the alleys, wool mulch in the planting row, and planting into a dead cover crop. 30

31 Weed Control in Bearing Fields In spring, move straw mulch off rows into the alleys. Prompt removal of mulch leads to higher production and can also help inhibit the establishment of weeds germinating early in the season. Remove enough straw so that strawberry leaves turn green immediately, but not so much that the soil is bare. A thick layer of straw in the alleys can keep weed pressure down until summer. Straw also helps keep fruit (and customers knees) clean, and reduces diseases. Several weeds can cause problems between straw removal and harvest. Dandelions and ox-eye daisies that sprouted the previous August should be removed by hand as soon as possible. Volunteer grain can be sprayed with a grass herbicide at 4 to 6 tall. Canada thistles should be pulled after they start forming flower buds in June. Quackgrass can be sprayed with clethodim for temporary control prior to harvest. After harvest, renovation provides a good opportunity to control weeds. 2-4,D amine products can be applied to control broadleaf weeds. If weeds are short, mow before spraying. If weeds are taller than the canopy, spray and wait five days before mowing. Once rows have been mowed and narrowed, and alleys have been cultivated, a pre-emergent herbicide can be applied to control weed seedlings that may germinate from seeds brought to the surface during renovation. Terbacil should be applied right away, but napropamide should be delayed until the middle of August so that it does not inhibit the rooting of daughter plants. Grasses should be sprayed when they are actively growing after renovation. Always wait four weeks between sprays of Terbacil and grass herbicides. Fall can be a time for weed control, before applying straw mulch for winter. If weather in early November still has day temperatures above 55ºF, 2,4-D may be applied if there is a high population of broadleaf weeds such as dandelions or shepherds purse. A pre-emergent herbicide can be applied in late October or early November, right before mulching for winter, to prevent establishment of weeds germinating the following spring. Buy clean straw for mulch! Clean, weed-free straw is always worth the extra expense. Straw with many weed seeds will bring headaches and expenses that will last for years. If you can t find straw that you know is weed free, you d be better off using an inferior but weed-free mulching material, such as chopped corn stover. Growers may choose to produce their own straw, so that they can be sure it s clean. However, an acre of spring-planted wheat or fall-planted rye will yield 3-5 tons of straw (dry weight). This is enough to mulch one acre of strawberries. For most growers, growing their own straw will only supplement the purchase of straw for mulch. A relationship with a producer of wheat or rye is worth developing as part of a weed control strategy. Certified grain seed producers can be a good source of high-quality, weed-free straw. The USDA has a website with descriptions of all major weeds found in the United States: A British organic farming organization has excellent descriptions of major weeds and good suggestions on non-chemical weed control: 31

32 8. IPM in Day Neutral Strawberries NEARLY all the strawberries grown in Minnesota are June bearing strawberries. Flower buds in June bearing strawberries are initiated during the short days of September and October, and the plants only produce one crop during a 2-3 week period. In day neutral strawberries, flower buds are initiated as long as the plant is actively growing. Peak production in day neutral strawberries occurs from August through October. The market for strawberries is lower in August than in June, but some people can profitably raise and sell day neutrals at farmer s markets or grocery stores. One of the biggest challenges of late summer strawberry production is that pest pressure is higher in August than in May. Tarnished Plant Bug The second generation of tarnished plant bug has already started laying eggs by the end of July, and the population of TPB can be ten times greater in August than in May. In conventional systems, day neutral strawberries should be sprayed with an insecticide that has a short pre-harvest interval such as malathion or benthrithrin when nymphs exceed a threshold of one per four blossom clusters. Other Insect Pests Picnic beetles mature too late in the summer to bother June bearing strawberries. By early July, their numbers can be fairly high. Picnic beetles only eat strawberries with skin that has been cracked or otherwise damaged. The beetles burrow into the fruit, and congregate in large numbers. Spraying picnic beetles is nearly impossible, because the insects are often hidden in decaying fruit. The most common means of control is using bait traps with vinegar and an insecticide. Multicolored Asian Lady Beetles feed on aphids and other insects most of the summer, but when soybeans dry up in August, they may feed on fruit, including strawberries. Diseases Anthracnose is common in day neutral strawberries. Fungicides should be sprayed before or after thunderstorms to prevent anthracnose. Gray mold is less common in day neutral strawberries, because the plant canopy is more open, and flowers can dry out quickly after rainstorms. Organic Options Growing day neutral strawberries without synthetic fungicides or insecticides is difficult. In other parts of the world, most day-neutral strawberries are grown under plastic, either as high tunnels with plants in the ground, or plants on tables. By growing plants under high tunnels, gray mold will be sharply reduced, and anthracnose will be eliminated. TPB nymphs must be controlled with organically approved insecticides in high tunnels. The potential for spider mite damage is greater for strawberries grown under plastic than field grown strawberries. The biggest problem in growing strawberries under plastic is keeping the temperature cool during hot days in July and August. 32

33 9. Organic Systems for June Bearing Strawberries JUNE bearing strawberries can be grown in Minnesota without synthetic pesticides or fertilizers. There are two systems that have been economically successful: single year cropping or Finke system, and the perennial system. The Finke System - Single Year Cropping Doug Finke and Diane Felde-Finke were conventional strawberry growers who slowly converted to organic production on their farm near Duluth. They first stopped spraying herbicides, then fungicides, and finally eliminated insecticides. For them, the easiest way to raise strawberries organically is to only crop their fields one year. They use the matted row system common in Minnesota, but instead of keeping their fields in production three years, they plow under their fields after the first harvest. Doug and Diane Finke Like all successful organic strawberry farms, Doug and Diane use cover crops and tillage to kill perennial weeds in fallow fields. In fields with quackgrass or thistle, they keep their fields tilled all summer. Their fields are flat, limiting the potential of erosion in fallow fields. They found that eliminating perennial weeds is a slow process, but over the course of 20 years they have managed to control almost every major weed in their fields. In fields without perennial weeds, they plant rye or rye-vetch mixtures into their fallow fields, which overwinter and must be plowed in the spring. In order to control annual weeds, Doug uses tilling equipment from planting until runnering. The primary cultivation equipment he uses is the Budding in-row weeder. The in-row weeder only kills small seedlings, so it must be run a minimum of once a week. After the plants begin to runner, they hire workers to hoe and weed the fields. By the end of July, the plants are starting to fill in the rows, and little weeding is necessary. In order to control insects, Diane monitors every field every day for tarnished plant bugs during bloom. In over a decade, they have never exceeded the threshold of 1 nymph per 4 clusters, so they have not had to spray. Their low insect pressure is due to a combination of forests near the field, and regular mowing of the grass parking lots and driveways between the forest and the fields. The grass never grows tall enough to become a breeding ground for TPB. The woods are a poor habitat for TPB, but a good habitat for clipper weevils. By only cropping their fields once, they have eliminated the clipper weevil problem. Clipper weevils are rarely a problem in fields in their first year of production, except on outside rows. By only cropping one year, they also eliminate the potential for cyclamen mite damage. 33

34 So far, Doug and Diane have never had a gray mold outbreak. There are several possible reasons why they have avoided major disease problems. The biannual planting system keeps gray mold spores from building up in the fields. Diane sprays calcium and potassium sprays from bloom through harvest to prevent gray mold. They use enough finely chopped straw so that fruit never touches the ground. Their ground is flat and sandy, and they never get enough standing water to cause leather rot. Their plants are healthy and able to fight off many diseases. The Finke system is not ideal for every strawberry farm (Table 3), but it works well if the strawberry yields drop between the first and second year of production. Table 3. Advantages and Disadvantages of Single Year Rotation Advantages Low gray mold pressure Low clipper damage No cyclamen mite damage Easy fertilization Disadvantages High establishment costs Large land requirement No contingency for bad planting year Difficult weed management Organic Production Using Long Rotations Laura and Brian Wilson of Alexandria, MN, have been growing strawberries organically for five years, and have kept one field in production for four years. Laura and Brian planted their field on a hill with a south and west exposure, which allows the plants to dry off quickly following rainstorms. Their fields are planted on virgin ground, and perennial weeds were killed by summer tillage. Before planting, they applied several tons of compost per acre. Wilson s farm is surrounded by alfalfa fields and pasture, so they have higher TPB pressure than Finkes. Laura monitors for TPB. Most years, the TPB nymphs hatched after the strawberries bloomed, and they have had few insect problems. There are a large number of beneficial insects in their fields during bloom. Laura and Brian plant multiple varieties of strawberries in order to spread their risks out. After an infestation of thrips, the Jewel and Glooscap remained healthy, while other varieties were severely damaged. They renovate by mowing the plants after harvest and tilling between the rows. They must spend time in the fields pulling perennial weeds in late summer. They have had few disease problems. The low disease pressure can be partly explained by planting on a hilltop with good air movement, and by having healthy plants. 34

35 10. Red Raspberries RASPBERRIES and strawberries are closely related and are damaged by similar insects and diseases. Minnesota is at the northern edge of commercial red raspberry production and the northern two thirds of the state is too cold for black raspberry production. As a result, raspberries have few diseases and most small raspberry producers spray no fungicides or insecticides. The most common fruit disease in red raspberry is gray mold. In Minnesota, gray mold can be mostly controlled by planting raspberries in sites with good air circulation. Few Minnesota raspberry producers spray for gray mold. Leaf and cane diseases in raspberries are different than in strawberry. Canes are usually infected in the first two months after sprouting in May or June. On a summer bearing cultivar, the disease stays in the cane for two growing season. Always try to control cane diseases during the first summer. During moderate infections, diseased canes can be removed. During a bad infection, the plants must be sprayed with a fungicide. The best time to spray is when new canes are 6-12 tall. Leaf and cane diseases in summer bearers can be minimized by using alternate year mowing. In alternate year mowing, growers mow their canes in late winter on half of their producing acreage, so half the field will be all primocanes (first year canes) and the other half a mixture of primocanes and producing canes. Many growers have started using alternate year mowing as a labor saving tool, because they skip the labor intensive step of removing dead canes after harvest. Alternate year mowing also decreases leaf and cane diseases. The new summer bearing cultivar, Nova is resistant to many cane and leaf diseases. Raspberry root diseases are similar to those found in strawberries. The most common root disease in Minnesota is phytophthora, which stunts plants similar to black root rot in strawberries. Phytophthora can be minimized by planting in well drained soil. Lime will sharply reduce phytophthora in acidic soils. In neutral soils, gypsum will help control phytophthora. Latham is resistant to many phytophthora fungi. Viruses are always a threat to raspberry plants. Raspberries live for decades, and viruses can build up in raspberry plantings. Wild raspberries can serve as a source of viruses, so try to plant raspberries away from wild plants or remove the wild plants. Always buy certified plants from reputable nurseries, and try to avoid transplanting raspberries from an old bed. Fruit insect pests include tarnished plant bug and picnic beetles. The damage from tarnished plant bug is minor compared to strawberries and results in dried drupelets. Picnic beetles hide under the caps. Keeping the raspberries cleanly picked reduces the number of picnic beetles. In late August, multicolored Asian lady beetles will fly into fall bearing raspberry plantations, and must be controlled chemically. Weed control is essential for first year raspberries, and there are few effective herbicides labeled for first year raspberries. Many of the same guidelines for strawberries also apply to raspberries. Always plant in a clean field with no thistles or quackgrass. For the first month after planting, weeds should be controlled by tillage. After the first canes start growing, a straw mulch can be applied around the plants. The straw mulch will be thick enough to smother annual weeds like crabgrass or redroot pigweed, but thin enough that the raspberry canes will grow through the mulch. 35

36 Appendix 1: Pesticide Options for Strawberries - Overview Pesticide Labels All pesticides have a common name and a brand name. The common name is the active ingredient, while the brand name refers to the combination of active ingredients and inert ingredients in the pesticide formulation. Occasionally, the common name and brand name are the same, as with most brands of the insecticide Diazinon. Many times, two or more pesticides have different brand names but have the same active ingredients. For example, the herbicide Clethodim is sold as both Select and Arrow. Some fungicides have more than one active ingredient. The following appendices are provided as an aid to growers. Because pesticides labels can change, always check to make sure that the pesticide is currently labeled for use on the particular crop and site before buying and/or using it. Also, before buying and using any pesticide product, read the label carefully. The label is the final authority on how you may legally use any pesticide. The Minnesota Department of Agriculture does not endorse the use of any specific product. New Pesticides Old, broad spectrum pesticides are slowly being phased out and being replaced by new pesticides with unique modes of action. The new pesticides are more expensive, but are usually more effective than their predecessors. Most new fungicides are able to cure diseases that have already started. Many new insecticides kill fewer beneficial insects. Timing is essential with many new insecticides. Resistance management is important in the new fungicides. The best way to avoid fungicide resistant fungi from building up in the fields is to either mix the fungicides with Captan or Thiram, or to alternate fungicides from different groups. The following lists are intended to provide examples of the many products and classes of pesticides that are now available to strawberry growers and that could be integrated into conventional pest control programs in Minnesota berry fields. 36

37 Appendix 2: Herbicides for Strawberries - Planting Years (Establishment) Chemical DTH/ PHI Acre Rate REI Comments PRE-EMERGENCE HERBICIDES Dacthal 75W (DCPA) 3 days 8-12 lb. 48 hrs. Apply in spring after planting. Must be down to weed seed zone to be effective. Consider banding over the row to reduce cost. If rainfall does not occur in 5 days, irrigate in Devrinol 50W 10G 2EC (napropamide) 42 days 4 lb. 20 lb. 1 gal. 12 hrs. Only works if applied to bare soil. Can be tilled in prior to planting. After planting, must be watered in within 24 hours. May be applied to newly planted berries at 4-lbs. per acre or ½ full rate. Another application of 4 lbs. may be made after ample daughter plants have rooted. Sinbar 80W (terbacil) 70 days 2-3 fl. oz. 12 hrs. Many varieties have shown some injury to Sinbar especially on sandy soils. 2-3 oz. may be applied from planting until runnering. Irrigate off leaves immediately. May also be applied in fall when plants are dormant. Soils should have over 2% organic matter. Maximum annual use is 8 oz. Chateau (flumioxazin) 30 days pre-plant 3 oz. 12 hrs. Phytotoxic after planting POST-EMERGENCE HERBICIDES Select 2EC (clethodim) Roundup (glyphosate) Fusilade-2L (fluazifop-butyl) 4 days 6-8 fl. oz. plus crop oil concentrate (COC) 14 days Depends on Formulation 365 days fl. oz. + 1% crop oil concentrate (COC) Apply to actively growing grasses at least 4 inches tall. Maximum annual use is 32 ounces per acre. Must be used with crop oil concentrate of at least 1% water volume. Works well on quackgrass. 12 hrs. Use to control hard to kill weeds such as thistle and quackgrass the year before establishment. Glyphosate cannot contact strawberry plants or severe injury may occur. 12 hrs. Do not apply to strawberries that will be harvested within one year of application. Works well on quackgrass. Abbreviations: DTH=days to harvest, PHI=pre-harvest interval, REI=reentry interval NOTE: Pesticide labels can change. Always check to make sure that the pesticide is currently labeled for use on the particular crop and site before buying and/or using it. Also, before buying and using any pesticide product, read the label carefully. The label is the fi nal authority on how you may legally use any pesticide. 37

38 Appendix 3: Herbicide Options for Strawberries DTH/ Chemical PHI PRE-EMERGENCE HERBICIDES Dacthal 75W (DCPA) Devrinol 50 DF 10G 2 EC (napropamide) Sinbar 80W (terbacil) POST-EMERGENCE HERBICIDES Formula 40 Amine 4(2,4-D) Poast (sethoxydim) Select 2EC, Arrow 2EC (clethodim) Roundup (glyphosate) Gramoxone Extra* (paraquat) Scythe (pelargonic acid) Chateau WDG (flumioxazin) - Production Years (Bearing) Acre Rate REI Comments 3 days 8-12 lb. 48 hrs. Apply in early spring. Must be down to weed seed zone to be effective. Consider banding over the row to reduce cost. 42 days 8 lb. 40 lb. 2 gal. 12 hrs. Apply in late fall or early spring. Must be down to weed seed zone to be effective. Irrigate within 24 hours of application. Devrinol rapidly degrades in sunlight. 110 days 2-6 fl. oz. 12 hrs. Many varieties have shown some injury to Sinbar especially on lighter soil. Recommend trying on small area on your farm first. Apply only to dormant plants or after mowing at renovation. Soils should have over 2% organic matter. Maximum annual use is 8 oz. Only used after harvest 7 days pts. + Crop Oil Concentrate (COC). 4 days 6-8 fl. oz. + Crop Oil Concentrate (check label -some formulations contain COC) 14 days Depends on formulation. 21 days Consult dealer for upcoming formulation. 5 days 3-5% for annual weeds 5-7% for perennials weeds 7-10% max burn down 2-3 pt. 48 hrs. Use only approved forms of 2, 4-D such as Formula 40 and Amine 4. Kills some broadleaf weeds. See text if spraying at renovation. Use gallons of water per acre. May also be used on dormant strawberries. 7 days Apply when grasses are actively growing, 4-6. Sinbar and Poast should be sprayed 6 weeks apart. Maximum/season is 2½ pints per acre. Always use crop oil concentrate with Poast. Apply to actively growing grasses at least 4 tall. Use low rates for annual grasses, high rates for quackgrass. Maximum annual use is 32 oz. per acre. Must be used with crop oil concentrate of at least 1% water volume. 12 hrs. Use to control hard to kill weeds such as thistle and quackgrass. Glyphosate cannot contact strawberry plants or severe injury may occur, especially in fall. 12 hrs. Destroys green plant tissue contacted with spray. Shield to protect strawberries. May be used to narrow rows at renovation. Maximum use is 3 times per season. 12 hrs. Apply between rows to control weed or narrow strawberries. Use shields to protect desirable plants N/A 3 oz. 12 hrs. Phytotoxic. On actively growing plants, apply as a hooded or shielded sprayer application to aisles. Stinger (clopyralid) 28 days 1/3 2/3 pt. 12 hrs. Do not tank mix with any other product! Some cultivars like Annapolis are susceptible. Stinger stays in soil for months *Restricted use pesticide - must have pesticide applicator s license to purchase and apply. Abbreviations: DTH = days to harvest same as PHI=pre-harvest interval, REI=Reentry interval NOTE: Pesticide labels can change. Always check to make sure that the pesticide is currently labeled for use on the particular crop and site before buying and/or using it. Also, before buying and using any pesticide product, read the label carefully. The label is the fi nal authority on how you may legally use any pesticide. 38

39 Appendix 4: Insecticides for Strawberries Treatments* Tarnished Plant Bug Malathion EC (malathion) Thiodan 3EC (endosulfan) Phaser 3EC (endosulfan) Brigade 10W(bifenthrin) Dibrom 8EC (naled) Pyrelin EC Strawberry Bud Weevil Lorsban-4EC (chlorpyrifos) Danitol 2,4EC (fenpropathrin) Brigade 10W(bifenthrin) Spittle Bug Thiodan 3EC (endosulfan) Sevin XLR (carbaryl) Danitol 2,4EC (fenpropathin) Cyclamen Mites Thiodan 3EC, Phaser 3EC (endosulfan) Diazinon Kelthane (Dicofol) Twospotted Spider Mite Kelthane 50 WFS (dicofol) Vendex 4L (hexakis) Agri-Mek 15EC (abamectin) Savey WP (hexythiozox) Zeal (etoxazole) Strawberry Rootworm Sevin 50WP (carbaryl) Sevin 80WSP (carbaryl) Leafhoppers Most insecticides effective against other strawberry insects are effective against leafhoppers. Strawberry Rootweevils Biological larvicides (parasitic nematodes) Danitol 2,4EC (fenpropathrin) Brigade WSBOW (bifenthrin) Aphids Thiodan 3EC, Phaser 3EC (endosulfan) DTH/ PHI 3 days 4 days 4 days 1 day 1 day 2 days 21 days 2 days 1 day 4 days 1 day 2 days 4 days 3 days 3 days 2 days 3 days 3 days 1 day 1 day 1 day Acre Rate REI Comments pts qts. 2 lbs oz. 1 pt. 1-2 pts. 2 pts oz ox qts qts oz qt. in minimum of 200 gal.water 3-4 lbs. 1-2 lbs pts. 16 oz. 6 oz. 2-3 oz. 2 lb lb. 12 hrs. 12 hrs. 48 hrs.. 48 hrs. 12 hrs. 12 hrs. 12 hrs. 12 hrs. 12 hrs. Refer to Tarnished Plant Bug sprays. 2 days 1 day Refer to dealer for updates fl. oz fl. oz. Begin treatment at 0.25 nymphs per cluster or 1 out of 4 clusters with 1 or more nymphs. Start monitoring when bud appears. In fields with a history of clipper damage, a pre-bloom spray is advisable. Begin scouting at first blossom. Economic threshold is 6 clipped buds per 3 row. Spittle masses are not desirable in pick-your-own operations. Consider treatments at 1 mass per square foot of row. Controlling weeds keeps insects in check. Cyclamen Mites feed on newly emerging leaves in plant crowns. Best control is in early spring and at renovation. Always use 200 gallons of water per acre with insecticide. Use gallons water/acre. Chemical must contact all surfaces of plant and leaves to be effective. Apply when leaf damage is apparent. Usually late July August. Only spray during bad infestations in June or July. Monitor plants and spray when small nymphs are feeding on the underside of the leaves. Biological larvicides are best-applied early May and late September or October. Chemical treatments are best applied mid-june to early July. Weevils are usually active at night. Look for leaf damage. 4 days 1.33 qt. Apply before bloom. Aphids are often controlled when chemicals are used for tarnished plant bugs. White Grubs Admire (Imdacloprid) N/A oz. 12 hrs White grubs are primarily a problem in first year plantings. Slugs Deadline (metaldehyde) Ferramol, Sluggo, Escargo (Iron Phospate) 1 day none lb. 40 lb. 12 hrs. 12 hrs. Apply before fruit ripens. *Some chemicals are made in other formulations and are also registered for use. Abbreviations: DTH=days to harvest, PHI=pre-harvest interval, REI=reentry interval 39

40 Appendix 5: Fungicides for Strawberries Treatments* DTH/PHI Acre Rate REI Comments Botrytis Fruit Rot (Gray Mold) Elevate 50WDG (fenhexamid) Switch 62.5WG (cyprodinil+fludioxinil) Topsin M 70WP (thiophanate-methyl) Plus Captan Captan 50W Captan 80W Captan 4L Thiram 65WP (thiram) Scala (pyrimethanil) Pristine (pyraclostrobin+boscalid) Leather Rot Ridomil Gold EC (mefenoxam) Aliette 8 WDG (fosetyl-a1) Pristine (pyraclostrobin+boscalid) ProPhyte (potassium phosphate) Leaf Spot and Leaf Scorch Nova 40W (myclobutanil) Thiram 65WP (thiram) Cabrio (pyraclostrobin) Topsin M 70WP Quadris or Abound (azoxystrobin) Anthracnose Quadris (azoxystrobin) Cabrio (pyraclostrobin) Captan 50W Pristine (pyraclostrobin+boscalid) Switch 62.5WG (cyprodinal+fludioxinal) Angular Leaf Spot (Bacterial) Bordeaux mixture (6 pounds copper sulfate and 6 pounds hydrated lime per 100 gallons of water.) Fixed copper different formulations available. Powdery Mildew Nova 40W (myclobutanil) Cabrio (pyraclostrobin) Elevate 50WDG (fenhexamid) Red Stele Ridomil Gold EC (mefenoxam) Aliette 8 WDG (fosetyl-al) ProPhyte (potassium phosphite) 0 days 0 days 1 day 1 day 1 day 1 day 3 days 1 day 1 day 0 days Before fruit set 0 days 0 days 0 days 1 day 1 day 1 day 1 days 0 days 1 day 0 days 1 day 0 days 12 days 1.5 lb fl. oz. 8 fl. oz. 6 lbs. 6 lbs. 5 lbs. 3 qts. 5 lbs. 18 fl. oz oz 1 pt lbs oz. 2-4 pts. 2.5 fl. oz. 5 lbs fl. oz. 8 fl. oz fl. oz fl. oz fl. oz. 6 lbs oz fl. oz. 4 hrs. 12 hrs. 12 hrs. 12 hrs. 48 hrs. 12 hrs hrs. 4 hrs. 12 hrs. 24 hrs 12 hrs. 1 day 1 day 1 day 0 days 0 days 0 days 2.5 fl. oz. 14 fl. oz. 1.5 lbs. 1 pt lb. 2-4 pts. 4 hrs 48 hrs. 12 hrs. 0 Timing of Gray Mold sprays is critical for success. Apply at 10% bloom and 50% bloom. Use additional sprays in wet seasons. Captan can be mixed with all products except Thiram to reduce fungicide resistance. Multiple sprays of Captan or Captec can leave residues on foliage. Captec and crop oil adjuvants can damage leaves. Apply at fruit set. Apply after early bloom at 7-14 day intervals. Use these products with good cultural practices such as excellent straw mulch. Follow label directions. Choose resistant varieties if possible. Rarely exceed economic thresholds. Provide good straw mulch and air circulation, spread by splashing raindrops or irrigation. Begin control when disease is in very early stage. Maximum of 4 applications per season. Caused by rain splashed bacterium. Can spread rapidly under cool, wet conditions. Monitor crop for injury when using copper. Caused by a windborne fungus. Diagnosed by upward curling of leaves and a white powdery mildew growth on the leaf. Red Stele is rare in Minnesota. Develops and is active in extremely wet soils, provide excellent drainage, chemicals will not give excellent control of Red Stele in wet soils. See label for specific directions. Abbreviations: DTH = days to harvest same as PHI=pre-harvest interval, REI=Reentry interval NOTE: Pesticide labels can change. Always check to make sure that the pesticide is currently labeled for use on the particular crop and site before buying and/or using it. Also, before buying and using any pesticide product, read the label carefully. The label is the fi nal authority on how you may legally use any pesticide. 40

41 Appendix 6: References and Suggested Readings Compendium of Strawberry Diseases. Second Edition, J.L. Maas (Editor). The American Phytopathological Society. St. Paul, MN (~$49) Cornell Fruit Resources - Berries has great information about strawberry IPM and weed management. Web site: Facts for Fancy Fruits is a great newsletter from Purdue. Available free at: Check out the August 2001 issue for a good discussion of fall herbicide options. subscriptions are free; printed and mailed subscriptions are not. You can subscribe either way at the website. Field Guide for Identifi cation of Pest Insects, Diseases, and Benefi cial Organisms in Minnesota Strawberry Fields Web site: The Midwest Small Fruit Pest Management Handbook from Ohio State has a good weed control section, and a whole lot more. The discussion of cover crop possibilities is better than any I ve found elsewhere. Web site: Production Guides Strawberries: Organic Production can be ordered from ATTRA: Appropriate Technology Transfer for Rural Areas The publication can also be printed off the ATTRA web site at: Strawberry Production Guide for the Northeast, Midwest and Eastern Canada is still the definitive manual for strawberry growers and everyone should have access to it! The weed management chapter is very good. You can order this manual online for $45 + S&H through the Natural Resource Agricultural and Engineering Service (NRAES) / Cornell University at: or call the NRAES Cooperative Extension Strawberry Production Systems is a guide for growing organic produce from Cornell University. Web site: Strawberry IPM Web Sites University of California University of Illinois 41

42 Weed Identification Guides These publications from the University of Minnesota Extension Service are available from your county Extension office or online. Weed Seedling Identification Web site: Annual Grass and Perennial Weed Identification Web site: Annual Broadleaf Weed Identification Web site: Weed Emergence Sequences Web site: Sources of Weed Free Straw Minnesota Registered and Certifi ed Seed Directory is an annual publication you can obtain without charge from the Minnesota Crop Improvement Association, 1900 Hendon Avenue, St. Paul, MN or , from county offices of the University of Minnesota Extension Service, or online at: 42

43 Appendix 7: Sources of Pest Management Supplies Traps and Lures Great Lakes IPM Church Road Vestaburg, MI Phone: Toll Free: Fax: Web site: com (traps, lures, and fi eld supplies) UAP Great Lakes N15721 Schubert Rd. Galesville, WI Phone: Web site: (traps, lures, chemicals, and fi eld supplies) Trecé Inc Hwy 28 W. P.O. Box 129 Adair, OK Phone: Fax: Web site: (manufacturer of pheromone lures and traps) Beneficial Insects Beneficial Insectary 9664 Tanqueray Ct. Redding, CA Phone: Toll Free: Fax: Web site: (green lacewing, Trichogramma wasp) Rincon-Vitova Insectaries, Inc. P.O. Box 1555, 3891 Ventura Ave. Ventura, CA Toll Free: Fax: Web site: (Trichogramma wasp, other benefi cial insects) Field/General Supplies Applecraft Orchard Supply th Ave. So. Minneapolis, MN Phone: BioQuip Products 2321 Gladwick St. Rancho Dominguez, CA Phone: Fax: Web site: Gempler s 100 Countryside Drive P.O. Box 270 Belleville, WI Toll Free: Web site: Spectrum Technologies, Inc W. Andrew Road Plainfield, IL Phone: Toll Free: Fax: Web site: (Leaf wetness/temperature loggers, PH meters, etc.) 43

44 44... Notes

45 ... Notes 45