Powdery mildew -- a fungal infection capable of decimating cucumbers, squashes, pumpkins and melons -- has come to call. If you suspect that your cucumber plants have powdery mildew, it is too late for prevention, but you can still save your crop. The highest risk levels occur when conditions are cloudy with rainfall likely, which favor the survival and deposition of the downy mildew inoculum. Luckily, there are less drastic measures you can take to rid your garden of these pesky fungi. http://msue.anr.msu.edu/news/cucumber_downy_mildew_makes_an_early_appearance_in_michigan. April 2015. 3 Keinath, A.P. Garlic. Rinse your pruning tools in rubbing alcohol between cuts so they don’t spread the spores. It affects any type of cucurbit, but is less common in melons and cucumbers.The characteristic white, powdery mold is pretty easy to spot, but management and prevention of the disease requires several steps. » Management requires an integration of cultural, resistance, and chemical methods. Since 2004, severe epidemics of downy mildew have occurred on cucumbers in the Eastern and Midwestern parts of the U.S. Milk is one of the best organic powdery mildew treatments. Figure 1. Figure 2. Cornell integrated crop and pest management guidelines for commercial vegetable production. Because the disease does not overwinter in many production areas but is blown in from areas to the south, the occurrence of the disease is not affected by crop rotation or post-harvest sanitation.5, Minimizing periods of leaf wetness can lower the incidence and severity of downy mildew. Symptoms of downy mildew on upper leaf surface. The Plant Health Instructor. Individual results may vary, and performance may vary from location to location and from year to year. In the U.S., the pathogen overwinters on live cucurbit plants in areas with mild winter climates or plants growing in greenhouse/protected culture environments. Gray to purple colored downy mold growth develops on the undersides of leaves (Figure 1). 2 Colucci, S.J. Powdery mildew completely covering this leaf. These epidemics have been caused by new strains of the pathogen that can overcome previously effective forms of resistance.4, Improved resistance to downy mildew has recently become available in slicing varieties such as SV3462CS, SV4719CS, and Bristol, and pickling varieties such as Citadel and Peacemaker from Seminis. 8 The cucurbit downy mildew forecast homepage. Its 6- to 8-inch slicing cukes are ready for harvest in about 63 days. Start when conditions are right for an outbreak and repeat twice weekly until they change. It is believed that the proteins in milk act like an antibiotic when exposed to sunlight, but more research needs to be done as to why it works. Growers should evaluate data from multiple locations and years whenever possible. This intermediate form of resistance should be used along with the application of effective fungicides to help ensure acceptable levels of control in situations of high disease pressure.7, Fungicide applications are most effective when used in combination with disease-resistant varieties and other methods of control. Symptoms of downy mildew on lower leaf surface. Rinse your pruning tools in rubbing alcohol between cuts so they don’t spread the spores. Several fungicides are available for controlling downy mildew, including both protectant and eradicant fungicides. Thus, the disease can be avoided, or impacts on yield reduced by planting early. 4 Reiners, S. and Seaman, A. Resurgence of cucurbit downy mildew in the United States: a watershed event for research and extension. The recommendations in this article are based upon information obtained from the cited sources and should be used as a quick reference for information about cucumber downy mildew. Downy mildew can affect plants of all ages, but in many growing regions it appears late in the season.1,2 The infection is mostly restricted to the leaves, but the resulting reduction in photosynthetic area causes stunting of plants, reduced yields, and sunscalding of the fruit following defoliation. Protectants, including chlorothalonil, copper-based compounds, and mancozeb, can be used alone to protect plants from infection early in the season. Prolonged exposure to full sun and temperatures above 90°F kill the disease. Prune and destroy all infected leaves and branches. Remove all plant debris from around the cukes. ‘Cool Breeze,’ a self-pollinating variety prized for making sweet pickles. It could harbor powdery mildew spores and reinfect the plants with the next wind or rain. Todays recipe is so simple and … The cucurbit downy mildew forecast is based on the presence of the pathogen in or near an area and large-scale weather systems. 5 Egel, D. S. 2016. Prune enough healthy branches that sunlight and air reach all the remaining leaves. For tips on eliminating the outbreak and preventing its return, read on.