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. Fungicides are required to control cucurbit downy mildew. Fruits are not infected, but those that form are small, and do not ripen properly. 2010. The disease was first reported in Italy in 2004, was reported in the U.S. in 2007 and 2008 and has been steadily increasing in prevalence, distribution, and economic importance since then. 85% potassium bicarbonate. 2015. Downy mildew on cucumber has been verified in Berrien County, which is located in southwest Michigan. No. Labeled for powdery mildew in greenhouse cucumber plus several insects and mites. The use of brand names and any mention or listing of commercial products or services in this publication does not imply endorsement by NC State University or N.C. A&T State University nor discrimination against similar products or services not mentioned. The highest risk levels occur when conditions are cloudy with rainfall likely, which favor the survival and deposition of the downy mildew inoculum. Figure 1. Figure 1: Downy mildew symptoms on cucumber leaves. Clemson Cooperative Extension. Downy mildew is an import disease, especially on cucumber, rockmelon and zucchini. 1982 and 1988 the estimated incidence of downy mildew on cucumbers in North Carolina was 30% (St. Amand and Wehner, 1991). Downy mildew severity (%) z,y Entire canopy Affected leaves Yield (fruit per plant) z,y Variety 28 Aug 6 Sep 14 Sep AUDPC 14 Sep AUDPC Marketable Total Straight Eight 27 a … Once established in a region, the disease can spread rapidly, causing significant loss of fruit quality and yield. These fungicides are no longer recommended for the control of downy mildew in most areas.4 Fungicides such as Presidio®, Previcur Flex®, Revus®, Curzate®, and Tanos®, are also less effective than they were, but still provide some control. 2016. reduction in photosynthetic activity early in plant development results in stunted plants and yield reduction This is because the pathogen spreads via wind-dispersed spores that can be moved long distances and be deposited by chance anywhere. Cucumber downy mildew incidence and severity were evaluated weekly within each field from June until September or October. DOI: 10.1094/PHI-I-2010-0825-01. April 2015. 6 Hausbeck, M. 2015. Identification of downy mildew can be more difficult in watermelon and cantaloupe than in cucumber since lesions do not always have the characteristic angular shape, but spores on the underside of the leaf can provide additional evidence of the pathogen. Downy mildew is a disease caused by the fungus-like water mold, Pseudoperonospora cubensis, which attacks only cucumbers and related crop species (gourds, pumpkin, squash, melons). In severe cases, powdery mildew can cause premature death of leaves, and reduce yield and fruit quality. Once the disease appears, eradicants that penetrate tissue will be needed.4 The downy mildew pathogen can develop resistance to fungicides fairly quickly, and products that provided good control only a few years ago are no longer as effective as they once were, including the phosphorus acid fungicides, fungicides containing mefenoxam (Ridomil Gold®), and the QoI/strobilurin group of fungicides (formulations of Quadris®, Flint®, Cabrio®, Pristine®, and Reason®). Be sure to obtain current information about usage regulations and examine a current product label before applying any chemical. Because downy mildew doesn’t survive the winter, the pathogen must re-emerge each growing season. Symptoms of downy mildew on upper leaf surface. Cucumber yield losses from downy mildew remained minimal com-pared to other diseases until 2004 when a more virulent Indians. In wet weather, it spreads rapidly, and is difficult to control. 8 The cucurbit downy mildew forecast homepage. Gerald Holmes, California Polytechnic State University at San Luis Obispo, Bugwood.org. Cooperative Extension is based at North Carolina's two land-grant institutions, Figure 1. Resurgence of cucurbit downy mildew in the United States: a watershed event for research and extension. This factsheet was prepared by the NCSU Vegetable Pathology Lab in 2013 with funding provided by Pickle Packers International, Inc. Find more information at the following NC State Extension websites: Publication date: Dec. 16, 2018 The downy mildew pathogen is an obligate parasite that needs living cucurbit plants in order to grow and survive. Determining the need and frequency of fungicide applications can be improved by the use of a disease forecast model, such as the one available at the Cucurbit Downy Mildew forecasting website.8. Plant Disease 99:4, 428-441. The forecast is based on an evaluation of the threat of inoculum production in source areas where the disease is present, and the risk of inoculum dispersal and disease development into areas along a projected trajectory of spread from the source areas (Figure 2). High disease pressure can significantly impact late season plantings.4, In the past, the use of disease resistance was very effective controlling downy mildew in cucumber, and today most commercial varieties have some level of resistance to downy mildew. Downy mildew of cucumber is caused by Pseudoperonospora cubensis, a member of the water mold group (Oomycota) of fungal-like organisms. » Management requires an integration of cultural, resistance, and chemical methods. This site is part of the IPM-PIPE (Integrated Pest Management Pest Information Platform for Extension and Education) network. Read our For slicing cucumber the varieties SV3462CS and SV4142CL. Leaves are severely affected, which can result in yield reduction or plant death. For pickling cucumber the varieties Citadel and Peacemaker from Seminis are tolerant to clade 2 isolates causing cucumber downy mildew. Downy mildew, caused by a fungal organism, and is most destructive to cucumber and cantaloupe, though all cucurbits are susceptible. 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. After disease is detected in your area apply fungicides at 5-day interval for cucumbers and 7-day intervals for other cucurbits. Figure 1. Recommendations for the use of agricultural chemicals are included in this publication as a convenience to the reader. Once the disease is reported in the state, using the highest rate labeled for products will result in better control and lower risk of fungicide resistance. Symptoms first appear as pale green areas on the upper leaf surfaces. After disease is reported in the state you can use: Ranman + Bravo, alternated with Previcur Flex + Bravo, alternated with Orondis Opti every 7 to 10 days, with the shorter interval if the weather is wet and cool. IL 90 – Rev. The cucurbit downy mildew forecast is based on the presence of the pathogen in or near an area and large-scale weather systems. 3 Keinath, A.P. Downy mildew Pseudoperonospora cubensis has been confirmed in the Great Lakes Region, a pickling cucumber crop in Berrien county, in Southwest Michigan. Powdery mildew, mainly caused by the fungus Podosphaera xanthii, infects all cucurbits, including muskmelons, squash, cucumbers, gourds, watermelons and pumpkins. In these regions, the pathogen arrives first in the more southern locations and makes its way northward, usually arriving in the Midwest and New York in late July, August, or September.4,5 Inoculum from infected, greenhouse-grown plants in the region may result in the disease showing up on field-grown plants earlier than would be expected.1,6, Infection and disease development occurs most rapidly during periods with moderate temperatures (59-68°F) and cool nights. Powdery mildew begins with a few white or grayish-white spots appearing on the foliage of plants. The pathogen is disseminated by windblown sporangia that can travel up to 600 miles in 48 hours on air currents.3, For the Eastern and Midwestern production areas, inoculum typically comes from southern Florida and Texas. Isolates belonging to clade 2 can quickly become resistant to fungicides, thus, fewer effective fungicides ara available for downy mildew control in cucumber and cantaloupe. Hausbeck closely monitors cucumber downy mildew to determine fungicide recommendations. The average value (US$) loss per year was 2.9% based on yield and quality reduction. These spots first appear on leaves at the center of the plant. The content of this article should not be substituted for the professional opinion of a producer, grower, agronomist, pathologist and similar professional dealing with this specific crop. Cucumbers are the m… For the latest fungicide recommendations for cucurbit downy mildew see the Southeastern US Vegetable Crop Handbook. Alternaria leaf blight on watermelon. Cucumber downy mildew (CDM) was confirmed on a cucumber sample from a production field in Wilson County on June 8 of 2020. Growers should evaluate data from multiple locations and years whenever possible. … Dr. Lina Quesada, NC State Vegetable Pathology Lab. Symptoms of downy mildew on lower leaf surface. 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