Rose Diseases and Insects in the Bradenton-Sarasota Area

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1 Rose Diseases and Insects in the Bradenton-Sarasota Area By: Philip Paul, CR The 10 bad actors in our area are the fungi and pests that some days slow down our enjoyment of our rose gardens. This issue is dedicated to understanding and fixing those problems. I have spent considerable time trying to look at the technology and then translate it into plain English that should be a long term helpful reference. You will note that each picture is bordered with a color. Let me explain the purpose of this. The color indicates the degree of severity that particular disease or pest has. A red border means, don t let this persist-it could kill the bush. Yellow indicates the problem is probably not life threatening but there will be some bad effects. There is no green as there is no point in reporting non-problems. Then last there is blue, which means it s a problem that is fairly easy to deal with. Each item attempts to answer all the same questions. The biggies are: What is it, what causes it, what are the effects of it, how severe is it (color code above), what are the symptoms, How do I treat it in both a small and larger gardens (usually a matter of cost), any local area observations, and any deeper references or HOT LINKS. Later on we list the chemicals to treat the problem, dosage and costs. You will find that having Lat Farr s Book The Southern Queen is the best next step for getting more detail. Secondly, you will find the Disease & Pest Reference Section of the B-SRS web site is the next deeper click in your research. To see some practical solutions, check the web site in the Member s Area and read the most recent Jim Small articles. Since spraying is often a requirement in fighting diseases and pests, here are a couple of important thoughts not often mentioned in talks or articles on spraying. 1. Be sure to fully cover yourself before spraying; skin, inhalation or ingestion are things to watch. Most problems occur through the skin. Be sure to cover eyes and skin. 2. When you spray it is not required that you spray each chemical separately, most of us use a cocktail. e.g. First, I assess the garden and if I don t see any insects it is always recommended that you don t use any insecticide this time. Second I mix two chemicals for Black Spot (see the Black Spot Article) usually a contact and a systemic solution. I always add a capful of Super Thrive and I use a Southern Ag Spreader Sticker. 3. The only time I break the insecticide rule is in the spring. I like to spray a round of Conserve just to stop any early Thrip action. 4. In the spring I also keep a small spray bottle mixed with Conserve so that at the first sign of thrips I can spray any suspected thrippy buds. I have not tried to cover all the problems. This represents the majority of what you will find in our area. We will pick up a couple of other problems in future issues.

2 Rose Diseases and Insects in the Bradenton-Sarasota Area What is it? Chilli Thrips y Category: Insect In October 2005 a new thrip arrived in Florida in the West Palm Beach Area called the Chilli Thrip. It apparently came in on a Hurricane. Since that time it has migrated across Florida and on to Alabama and Texas. IT IS LETHAL!! (Thus tagged RED) It can destroy a bush in a very short period of time. It is the number 1 destroyer of rose gardens. (1) While other forms of thrips will attack white, pink or yellow roses, the Chilli s will attack any rose. (2) look for multiple cane die-back (see below), bud damage on a red rose is a sure sign (see right), fresh buds will become brittle and drop off, leaves curl up and turn brown then drop off (right). Check your roses often (every day or two) Starting in April be ready to spray Conserve on the ENTIRE plant Small Garden: Apply Conserve Naturalyte at 4TBSP per gallon to roses at first signs Large Garden: Apply Conserve SC at ¼ to ½ teaspoon at first signs Limit to 10 applications per year for effectiveness Consider a first spraying in April as a preventative (1) See Jim Small article on Chilli Thrips (on the web) (2) See under Disease and Pest Reference (3) (Aren t you glad we have hot links??) Page 5 Bradenton Sarasota Rose Society Bulletin June 2008

3 What is it? Flower Thrips and Red Banded Thrips Category: Insect For many years we have put up with common thrips of two types. The flower thrips are tiny insects that scrape the flower bloom. The Red-Banded Thrip is differentiated by its effect, which is to drill small holes in the side of the new buds (epidermis). It also can distort the leaves and leave dark blotches on them. They destroy blooms and if untreated can get to the foliage. In extreme cases they can ruin an entire plant. (Flower Thrips) Look for brown edges on the buds of light colored roses (white, pink, yellow). Blooms may not open or will open deformed. (see right) (Red Banded Thrips) Look for a small 1/8 hole as if drilled in the side of a bud. Also look for dark colored blotches on leaves (see below right) In the spring patrol your garden often; the first signs will be brown bud tops. Immediately spray as described below. Small Garden: Use Conserve Naturalyte and mix spray with 4TBSP/Gallon. Large Garden: Use Conserve SC at ¼ to ½ teaspoon/gallon Both Conserve products will do the job, but for the small garden the Naturalyte version is much less expensive. DO NOT let this problem go unattended; it will destroy a whole bloom period Red Banded Thrip Damage Credit: University of Florida

4 What is it? Anthracnose Cool, moist and spring type weather encourages the growth of the fungus. Look for wet leaves with temperatures 70 to 80 degrees Foliage drops off and plant production slows How severe are the results: Moderate (Yellow) DO NOT CONFUSE WITH BLACK SPOT Initially leaf spots about ¼ in diameter, progress to purple/brown, then to light brown with a red or purple margin. These will eventually yellow and fall off. The spots are better defined than Black Spot and will have a light colored center circle that sometimes will drop off the leaf. This last characteristic will best help define the differences with Black Spot. Know the difference between this disease and Black Spot but treat them about the same with chemicals Small Garden: Try Immunox or Orthenex. If there is no success try one of the Large Garden chemicals Large Garden: Eagle 20EW, Compass or usual Black Spot remedies What is it? Botrytis Fungus grows in high humidity at temperatures between 65 and 75 degrees Dead blooms How severe are the results: Moderate (Blue) Buds and early blooms turn to a gray mold color and never produce Lat Farr reports that this often shows up on bare root roses, beware! I had it happen on a potted rose from out of state recently Category: Fungus Anthracnose does appear in our gardens Section on Disease and Pest Reference Category: Fungus (1) Lat Farr recommends Plant roses where they will receive morning sun (2) When you notice remove affected stems & blooms Small Garden: Same as below Large Garden: Dithane M45 or Mancozeb This fungus appears more often than most observe. Lat Farr The Southern Queen P Section on Diseases and Pest Reference

5 What is it? Powdery Mildew Category: Fungus Temperatures between 65 to 70 degrees and 98% humidity and Warm days and cool nights are ideal for the growth of the fungus Flowering may stop and bush growth will become stunted. Buds that open are distorted How severe are the results: Moderate (Yellow) Blister like spots on younger upper leaf surfaces Young leaves become twisted and a white powdery substance appears New buds may be dead The disease starts on the upper part of the plant and works its way down Plant you garden with good air flow and avoid crowding If possible remove the canes showing the symptoms Clean up old leaves from the ground Use fungicides early to get maximum help, not after a heavy infection Small Garden: Immunox, Remedy (Potassium Bicarbonate) What is it? Downy Mildew What is the cause: Downey Mildew occurs with moist cloudy conditions, brought on by wind and or water in COOL & DAMP WEATHER, humidity around 85% with temperatures between 65 and 80 degrees. All roses are susceptible. Can kill a bush if not treated How severe are the results: Severe (RED) Purple, red or brown spots on leaves, stems and/or blooms. Angular blotches. Starts in the top of the bush and moves lower, usually shows dead buds Remove & destroy any heavily affected areas of plant Reduce humidity below 85% if in a controlled environment Small Garden: Spray with Mancozeb every 3 to 5 days until spots are gone. Large Garden: Eagle 20EW, Banner Maxx, Honor Guard, Compass, Rubigan, Mancozeb An occasional problem in our local gardens, not an every year occurrence Go to the section on Diseases and Pest Reference Category: Fungus Large Garden: Mancozeb, Subdue, Compass An occasional actor in our environment, but serious when it appears Disease & Pest Reference Section on the site

6 What is it? Spider Mites These mites hide in mulch or soil around roses. They multiply in the heat and dry weather and can do great damage. The spider mites suck the sap from leaves, starting the process. Often CRs will tell you that mites get their start in well sprayed gardens because the insecticides indiscriminately kill both the good and bad insects, thus giving room to spider mites. They will defoliate a bush and may cause dieback if not completely kill the bush. How severe are the results: Can kill bush SEVERE (RED) Lower foliage will lighten up. Put a towel or sheet below the bush, then shake and look for small dots. They can also be seen with a magnifying glass on underside of leaves. Inspect leaves regularly, look on the undersides! Use a water wand and blast both sides of every leaf Use the water wand every 2 or 3 days Small Garden: Use the water wand first, and then a miticide Large Garden: Use a miticide such as Avid, Forbid, Floramite SC What is it? Aphids Category: Insect Category: Insect Aphids are small 1/8 or less insects. They may vary in color from green, yellow, brown, red, black or white depending on the species and the plants they are feeding from. They seem to travel in colonies so they are easy to distinguish. Aphids do reduce the plants ability to have adequate photosynthesis. Seldom are they a threat to the plant. They do stunt new growth and can deform the plant. How severe are the results: Insignificant to moderate (Blue) (All VERY expensive), see Southern Queen for more information. Keep looking at the underside of leaves in hot weather Lat Farr The Southern Queen P Select the Diseases and Pests Reference and then mites. Aphids thrive during the Purple Time of Year (the spring or fall). They love the new blooms and will leave the leaves with Honeydew which is the sap from the leaves they cannot consume. The substance makes the leaves sticky and it is easy to notice. The first and usually the only step is to keep up the use of a water wand. Small Garden: As above water wand, if not successful try insecticidal soap Large Garden: If they prove stubborn, use Mavrik, Merit or Sevin may work Aphids truly embody the term pest. In our area the water wand should work. Lat Farr says that systemic sprays work better than contact sprays Lat Farr s Book The Southern Queen P48