Here is the latest Pest Update for ornamental growers. I would like to give credit to Lee Bloomcamp from Syngenta for taking the time to provide this information for growers.
Leaf spots are prevalent now, as foliage ages and dies off. Unless plants are going to be sold soon, treatment for foliar diseases is unnecessary, especially for deciduous plants. Most leaf spot disease have long life cycles, and treating affected foliage now may not reduce leaf spot appearance. Use a systemic fungicide as a drench to protect new growth as it emerges for better long term control, and use fungicides preventatively to keep infection from occurring.
Powdery mildew is active, recently seen on Mexican petunia, verbena, Gerber daisies, goldenrod, snapdragons, and crape myrtle. This disease like cooler weather, with high humidity. Scout regularly and maintain a preventative fungicide application program on vulnerable crops. Mural, Palladium and Concert II are all very effective against powdery mildew and leaf spots, other good choices for PM include Milstop, Eagle, and Phyton 27.
Downy Mildew is also showing up. Salvias, basil, roses, coleus, and viburnum are some of the primary victims. Downy mildew is systemic, meaning that it lurks in the plant until conditions are right for spore production. That’s why fungicides are best used preventatively, curative rescue applications are often too little, too late for this fast-moving disease. Limiting leaf wetting, increased spacing and airflow, and removal of severely infected plants is also important.
Phytophthora, Volutella and other systemic stem and root diseases continue to be a problem across Florida. Extreme summer heat and the need for lots of irrigation are contributing factors. In woody plants and some herbaceous material, cutting in to the stem tissue can help with diagnosis- discolored tissue indicates possible Phomopsis, Volutella or other die-back diseases like Phyllosticta and Pestalotiopsis. Roots are often unaffected. With Phytophthora, roots are often discolored, and little to no evidence is found in woody tissue. Segovis is an outstanding addition to phythophthora rotations- fully systemic, drench and foliar applications, low use rates and a 4 hour REI. Bacterial disease symptoms can look like both. Consider getting a disease analysis done if problems are severe, as a number of things can cause general dieback associated with these diseases. Specific fungicides and cultural controls are needed, and time and money can be wasted on the wrong products and techniques!
Sanitation is key to disease prevention- clean up old, diseased leaves and cuttings to reduce inoculum, and be ready to treat new growth as soon as it appears. This is when many disease cycles begins, even if damage doesn’t appear until foliage has matured. Send samples off for diagnosis if problems are persistent. Knowing the disease involved helps to determine the best timing, cultural controls and fungicides for preventative applications.
I am also seeing secondary foliar symptoms that look like disease but are related to nutritional issues. Summer weather can deplete nutrients in even the best slow release fertilizers, and some micronutrient deficiencies can result from extreme soil pH conditions, and look like disease problems. Proper diagnosis of the problem leads to a quicker resolution- did I mention this already?
Insects and Mites
Caterpillars are evident in many crops this time of year. Species like Fall Armyworm, European Pepper moth and Cutworms have spring and fall population peaks, so check plants like ferns, poinsettias, bedding plants, gingers and other herbaceous perennials for caterpillar damage. Webbing, droppings and foliage damage at the soil line are good indicators. If uncertain, take the entire plant and soil out of the pot, and break it up into a bucket of water. Larvae, pupae, webbing and other debris will float to the surface for easy ID.
Water floatation is also a good way to survey for Azalea root weevil, and Flea beetle grubs, which often attack the roots of the same plants that host adults feeding on foliage. Grower feedback on Mainspring GNL for caterpillar and flea beetle control has been very good, looks like we have another tool for these pests! Mainspring GNL is labeled for foliar and drench applications, is systemic, and also has a 4 hour REI.
(Disclaimer-Mention of a commercial or herbicide brand name or chemical does not constitute a recommendation or warranty of the product by the authors or the University of Florida, Institute of Food and Agricultural Sciences, nor does it imply its approval to the exclusion of other products that may also be suitable. Products should be used according to label instructions and safety equipment required on the label and by federal or state law should be employed. Pesticide registrations may change, so it is the responsibility of the user to ascertain if a pesticide is registered by the appropriate state and federal agencies for its intended use.)