Addressing Widespread Damage to Turf, Wheat, And Nursery Crops by the European Chafer: Immediate Strategies and Long-Term Solutions

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1 Addressing Widespread Damage to Turf, Wheat, And Nursery Crops by the European Chafer: Immediate Strategies and Long-Term Solutions Project Number: Team Leader: Team Members: GR D. R. Smitley, Michigan State University Department of Entomology Chris DiFonzo, MSU Dept. of Entomology; Kevin Frank and Suleiman Bughra, MSU Dept. of Crop and Soil Sciences; and Tom Fernandez, MSU Dept. of Horticulture Justification The European chafer looks like a small June beetle and has the same type of larval stage; a C-shaped white grub that feeds on plant roots. It was discovered in the United States in Newark, New York in It has now spread throughout the states of Connecticut, New York, Pennsylvania, Ohio and Michigan, where it is a devastating pest of home lawns, municipal turf, and sometimes nursery crops, wheat, alfalfa and pastures. European chafer has rapidly expanded its range across Michigan over the last 5 years, destroying most of the turf in some subdivisions in the greater Detroit area, Ann Arbor, Jackson, Lansing, and Grand Rapids. For the first time in 1999, European chafer also caused substantial losses to some nursery, wheat, soybean and alfalfa fields. The most important short-term needs are for experiments to determine how to grow turf that is resistant to European chafer grubs, and how to avoid yield losses in nurseries and field crops. At the same time we will begin to seek long term solutions to this outbreak of European chafer. The incidence of pathogens and parasites in Michigan will be compared with that in New York State and Europe. Also, turf types that appear to be tolerant of European chafer grub feeding in greenhouse tests will be tested in field plots.

2 Results and Accomplishments by Objective MSU response team. The MSU team delivered new information about European chafer to turf, field crop and nursery clientele through an average of 12 Landscape Alert articles, 6 MSU extension conferences, 2 field days, and 2 in-service training programs for extension agents, and 8 magazine and industry newsletter articles, per year. Field crop growers were also reached by a survey on European chafer sent to key cooperators in each County. Find alternatives to Diazinon for spring and fall grub control. We tested thiomethoxam, a selective neonicotinyl currently being developed by Syngentis, as a less toxic and more selective alternative to Diazinon. In our nursery and turf plots it worked extremely well on European chafer when applied in July but not as well when applied in September (48%). Sevin (carbaryl) remains the most effective alternative for homeowners, giving 90% control when applied in the fall after September 1. We also began testing a new species of Steinernema nematode that has specificity for European chafer (with a cooperator at Rutgers University). After several tests, this nematode appears to be more active against European chafer than any other nematode that we know about. This work has now been published (Figures 1 and 2, Appendix I). Unfortunately, this nematode cannot be grown in artificial media, meaning that commercial production will depend on rearing nematodes in live grubs. However, the nematode can still be introduced by collecting infected grubs and introducing them to new areas. Irrigation as an alternative to Diazinon. Homeowners may be able to avoid grub damage to their lawns with consistent irrigation. In our experiment at the Hancock Turf Research Center 239 European chafer grubs were introduced in August and September to each of 18 plots maintained under 3 different irrigation practices. In November plots were sampled to determine grub survival. A mean of 22.1 grubs per ft 2 were found in the non-irrigated plots, 17.0 grubs per ft 2 in the plots irrigated once per week, and 8.2 grubs per ft 2 in the daily irrigated plots. Daily irrigation reduced the survival of European chafer by 63%, a level of control comparable to that obtained by applying Diazinon (Table 1, Appendix I)

3 Develop a method for screening turf for resistance to European chafer. New methods were devised for the testing of 18 cultivars of turfgrass in the greenhouse (3 cultivars each of: Kentucky bluegrass, perennial ryegrass, fine fescue, tall fescue, warm-season (C-4) turfgrasses, and commercially available native grass species). European chafer consumed between 5 and 95% of the grass roots over an 8-week test period. Six of the 9 most susceptible turf cultivars were either Kentucky bluegrass or fine fescue, the types of turf grown in 90% of all Michigan lawns. Tall fescue was more resistant to European chafer (Figures 3, 4 and 5, Appendix I). Similar results were obtained when this experiment was repeated the following year. Field tests are now needed to determine if tall fescue remains tolerant to grubs under lowmaintenance conditions typical of home lawns. Determine relationship between density of European chafer larvae in wheat and yield loss. Wheat was seeded into greenhouse pots at a density typical for crop production. The pots with wheat were immediately infested with grubs and placed into a wheat field. 1 or 2 larvae per pot (4 to 8/ft 2 ) reduced wheat seedling emergence by 25 to 40%. European chafer grubs were also used to infest plots in a wheat field. A density of 8 grubs/ft 2 reduced tiller weight by 34% (Figure 6, Appendix I). Quantifying losses in nursery stock due to European chafer feeding injury. Arborvitae and spruce liner plants were planted on Sep 21. Treatments (n=20) consisted of 0, 4, 8, 12, and 20 European chafer larvae/2 gal pot. Within 8 weeks most of the plants seeded with 4 or more grubs had lost 50 to 94 % of their root mass (Figure 7, Appendix I). By calculating the grams of root removed per grub, the roots of the largest plants in the experiment (100 g) will be completely consumed in about 700 days by one grub. Preliminary results from this experiment suggest that 4 grubs per small tree (2 foot-tall) are enough to cause serious injury. Spruce trees may be more susceptible than arborvitae. This is the first experimental data on how European chafer larvae affect tree roots. European chafer is much more destructive to nursery trees than previously understood. Sampling for pathogens and parasites of European chafer larvae at Michigan research sites. European chafer larvae were collected from a minimum of 10 ft 2 samples at 13 locations in Michigan, and one site in Connecticut. Milky spore (Bacillus lentomorbus) was observed at a single site, where the incidence was 18%. Entomopathogenic nematodes were also observed at a single site, at a rate of 5%. Gregarines, gut-dwelling protozoan pathogens, were observed in grubs from 36% of all sites. The species and perhaps genus of gregarine that we found is new. We are collaborating with Dr. Richard Clopton, Peru University in Nebraska, to publish a description of it. Pathogenicity of a new Gregarine pathogen of European chafer. Healthy European chafer larvae from a population where no gregarines have been found were placed into pots with grass and soil that were previously occupied by either healthy grubs or gregarine-infected grubs. After 22 days 38 of 42 grubs in pots previously

4 occupied by infected grubs were infected. There were no gregarines recovered from grubs in control containers. Fewer gregarine-infected grubs (54%) survived than control grubs (67%) (P=0.057). Weight gain may also be slower for gregarineinfected grubs (36.4 mg) compared with control grubs (45.1mg) (P=0.23). Another experiment in fall of 2001 with a larger number of replicates (n = 160) confirmed results of the initial test: European chafer larvae with gregarines grow more slowly and have a greater mortality rate (Table 2, Appendix I). Impacts This research gives homeowners some options for preventing turf loss from European chafer. First, homeowners can avoid grub damage by watering their lawns in July and August. If lawns are irrigated with 1.0 of water per week for 8 weeks, European chafer will not be a problem. Irrigation can be skipped on weeks when there is enough rain. This gives homeowners a way to protect lawns without the use of pesticides. For those with grubs that choose not to irrigate, carbaryl and imidacloprid insecticides are available at most garden centers, and provide a good alternative to diazinon. MSU Extension staff and garden center staff in Michigan are now well educated on how to scout for European chafer grubs in lawns, determine if enough grubs are present to cause damage, and how to irrigate lawns or apply insecticide correctly, if necessary. Experiments with European chafer grubs in wheat fields and nursery fields have demonstrated how destructive they can be. Spruce and arborvitae nursery fields can be sustain losses of more than 50% in the first 4 years after planting, with as few as 1 European chafer grub per plant. Nursery growers have been educated on how to scout for grubs and how to use insecticides to prevent damage, if necessary. In wheat fields, as few as 2 European chafer grubs per ft 2 can reduce yield by 16%. Because of the narrow profit margin in wheat production insecticide application is not desirable. More work is needed to investigate how the summer crop preceding fall wheat can be manipulated to deter European chafer beetles from laying eggs there. We have made excellent progress in identifying types of turfgrass that are tolerant or resistant to European chafer grubs. Some cultivars of tall fescue and Kentucky bluegrass tolerate European chafer grub damage better than other types of turf. The most tolerant cultivars of tall fescue can be used in low-maintenance lawns where irrigation is not an option. In high-maintenance sites, cultivars of Kentucky bluegrass with grub tolerance are also an option. A naturally-occurring digestive system parasite of European chafer was found to infect a very high proportion of grubs in Europe (90%+) and upstate New York (80%), a moderate proportion in southern Michigan (50%), and a low proportion (<10%) along the leading edge of the European chafer infestation in central Michigan. This suggests that the gregarine parasite is spreading naturally 5 10 years behind the spread of European chafer. This gives us an opportunity to enhance natural spread of the parasite by introducing it along the leading edge. Future work will focus on this opportunity. Summary Immediate relief from European chafer damage to lawns can be obtained by frequent watering of turf in July and August. The best long-term solutions are use of grub tolerant

5 cultivars of tall fescue and Kentucky bluegrass, and to introduce grubs infected with the gregarine parasite to the leading edges of the European chafer infestation in Michigan. Funding Partnerships Michigan Turfgrass Foundation $30,000 Dow Gardens $15,000 Michigan Department of Agriculture $ 3,000 Journal Publications From This Work: 1. Bughrara, S. S., D. R. Smitley, D. Cappaert and A. N. Kravchenko Comparison of tall fescue (Cyperales: Graminaeae) to other cool-season turfgrasses for tolerance to European chafer (Coleoptera: Scarabaeidae). J. Econ. Entomol. 96: Cappaert, D. L. and A. M. Koppenhofer Steinernema scarabaei, and entomopathogenic nematode for control of the European chafer. Biological Control 28: European chafer consumption of roots of warm season and native turfgrasses. Data analysis complete. Submit manuscript to Hort Technology by December Survival of European chafer in irrigated turfgrass. Complete data analysis and submit manuscript by April, Impact of European chafer larvae on yews, arborvitae and spruce. Data analyzed. Submit manuscript for publication by June, 2005.

6 Appendix I Figure 1. Efficacy of a new Steinernema sp. against European chafer. Black and white bars are European chafer; red and pink bars Japanese beetle. New Steinernema, dose trial 100% 80% Mortality 60% 40% 20% 0% Infective juveniles/larva Figure 2. Efficacy of a new Steinernema sp. against European chafer and Japanese beetle in a laboratory test. New Steinernema, dose trial 2 Mortality 100% 80% 60% 40% dark: 7 DAT light: 14 DAT B/W: EC color: JB 20% 0% Infective juveniles/larva

7 Table 1. Survival of European chafer grubs in turf plots that are not irrigated, irrigated once per week, or irrigated daily. Irrigations treatment Grubs/ft 2 Statistic s None 22.1 Weekly 17.0 Daily 8.2 df = 2,15 F = 3.7 P = Figure 3. Survival of European chafer larvae on 5 types of turfgrass (4 cultivars of each). KBG = Kentucky bluegrass, FF = Fine fescue, TF = Tall fescue, Rye = Perennial ryegrass, Nat = Native grasses, C4 = Zoysia, Bermudagrass or Buffalograss. Grub Survival 80% 70% 60% 50% 40% 30% 20% 10% 0% Daw Shad KY31 Quat Bons Fal Berm Bril Cham All Mid Aff PA Prem Zoy Pal LBS high low Buff Ind FF FF TF FF TF TF C4 KB KB KB Ry N Ry C4 Ry N C4 N Variety--decreasing order of mean survival

8 Figure 4. European chafer damage 5 types of turfgrass (4 cultivars of each). KBG = Kentucky bluegrass, FF = Fine fescue, TF = Tall fescue, Rye = Perennial ryegrass, Nat = Native grasses, C4 = Zoysia, Bermudagrass or Buffalograss. mean root damage, g Root Damage by Variety "root damage" = change in root w gt relative to control low high Ind Prem Buff Affin Berm Zoys Falc KY31 LBS Cham Palm Sedg Midnt Bons Quat Brill Daws Shad N Ry C4 Ry C4 C4 TF TF N KB Ry N KB TF FF KB FF FF Figure 5. European chafer consumption of turf roots. Data are mean amount of roots consumed for 5 types of turfgrass (4 cultivars of each): KBG = Kentucky bluegrass, FF = Fine fescue, TF = Tall fescue, Rye = Perennial ryegrass, Nat = Native grasses, C4 = Zoysia, Bermudagrass or Buffalograss. mean damage, g Root Damage by Turf Type C4 Rye Nat TF KBG FF Low High

9 Figure 6. Impact of European chafer larvae on yield of wheat in field plots. Wheat response to European chafer Weight (g) OR # tillers Dry Weight Tillers/plot Density--larvae/ft2 Figure 7. Consumption of Picea and Thuja roots by European chafer grubs. % Change in Root Mass vs Grub Treatment % Change in root mass 80% 60% 40% 20% 0% -20% -40% -60% -80% a a a b b bc c b b b Picea Thuja bc -100% Grubs/pot

10 Table 2. Experiments evaluating pathogenicity of gregarines in Japanese beetle and European chafer. Species Japanese beetle Japanese beetle European chafer Experiment al Set-up Larvae from 3 populations, individual cups, n=30/trt Uninfected larvae in groups of 5, n=20/trt Uninfected larvae, individual cups, n=160/trt Treatments 1. Uninfected 2. Gregarine 3. Gregarine + Ovavesicula 1. Gregarinefree soil 2. Gregarineinoculated 1. Gregarinefree soil 2. Gregarineinoculated Mean (SE) growth rate, mg/day 2.40 (.41)a 1.23 (.22)b 1.63 (.26)b 1.50 (.16)a 1.21 (.18)a.47 (.10).08 (.13) Mean survival 85% 61% 71% 55% 42% 52.5% 42.5%