This site is a project of the Cornell Vegetable Program Work Team (PWT). Margaret Tuttle McGrath 5: Yellowing, necrosis, and sporulation on basil leaves and flower bracts. Reason is the only one not permitted used on Long Island. Global production is at significant risk because of the lack of genetic resistance to this disease and the ability of the pathogen to be distributed on seed. To play it safe, it's a good idea to rotate your crop of basil and plant in an entirely new location for the next season. What Are These Black Spots on My Phalaenopsis Orchid Leaves, How to Treat and Prevent Black Spots on Roses, How to Get Rid of Powdery Mildew on Plants, Downy Mildew - a Problem for Impatiens Plants, Save Your Tomato Plants From These Common Diseases, How to Identify, Treat, and Prevent Clubroot, Preventing and Controlling Black Spot on Roses, How to Identify, Treat, and Prevent Anthracnose, 10 Common Rose Problems (and How to Fix Them), Identifying and Treating Leaf Spot Fungus on Magnolia Trees, How to Control Powdery Mildew With a Homemade Spray. It was reviewed and determined to be NOP compliant by Washington State Dept of Ag. The cucurbit downy mildew forecasting web site might be useful for predicting when conditions are favorable for basil downy mildew since both pathogens likely have similar requirements for successful wind dispersal long distances (e.g. High temperature is lethal to the pathogen. Any reference to commercial products, trade or brand names is for information only; no endorsement is intended. And Eurofins STA Laboratories in Colorado now tests basil seed for Peronospora spp. Part of the challenge of controlling downy mildew is the need for blemish-free herbs when marketed as fresh sprigs. and again in 1937 as P. lamii … Associate Professor Observations of downy mildew occurrence in field and greenhouse basil plantings suggest that environmental conditions can significantly affect severity of downy mildew. Leaves with yellowing resembling downy mildew but lacking spores can be placed upside down on a wet paper towel in a closed plastic bag in dark for a day to induce spore production, if the pathogen is present. Seed companies (including High Mowing Organic Seeds) are starting to steam treat basil seed. There is a 2(ee) recommendation allowing use of the new botanical fungicide EcoSwing (extract of Swinglea glutinosa) for downy mildew in field-grown basil. If you suspect your plants are infected with basil downy mildew and would like an expert diagnosis, you can bring an affected leaf to your local county or university extension office for positive identification. P. belbaharii is also seed-borne. School of Integrative Plant Science Maximum temperatures for infection, colonization, and spore production are 80 – 88 F. Research conducted in growth chambers demonstrated that temperatures up to 113 F kill spores and mycelium of the pathogen in affected plants, with length of effective exposure decreasing with higher temperature range, least being 6 – 9 hours at 104 – 113 F. Subsequently solar heating has been used to cure plants in Israel by closing greenhouse vents or using a transparent IR polyethylene sheet covering during sunny days. Quadris). Using seed not infested with the basil downy mildew pathogen, selecting a less susceptible variety, and applying fungicides are the primary management practices for downy mildew. This prevents water depositing on leaves when humidity is high. These include planting where there is full sunlight and good air movement with rows parallel to the prevailing wind direction, maximizing plant spacing, and using drip irrigation. Carefully pinch off a leaf and place it in a sealed plastic baggie for transport. Phosphorous acid fungicides can be tank-mixed with any of these greenhouse fungicides. Do not compost the plant or try to remove only the visibly affected leaves. MilStop, Regalia, and OxiDate are labeled for use outdoors and in greenhouses. Basil has been added to the list of herbs on the label for Cueva (10% copper octanoate). Yellow leaf tissue in bands delimited by large veins is distinctive for basil downy mildew. Drip irrigation is preferable to spraying because the leaves stay dry. Plant Pathology and Plant-Microbe Biology Section Ranman, Revus and phosphorous acid fungicides are permitted to be used in a greenhouse. Amy Jeanroy is an herbalist and professional gardener with several years of experience.