Cucumber downy mildew on cucumber was reported in Pennsylvania and Massachusetts between August 25 and September 12, 2023. CDM was reported on squash in N.C.
This disease was confirmed on squash in Johnson County, North Carolina on August 25, 2023. Disease incidence was approximately 15% and the affected leaves showed 45% disease severity.
As cucurbits continue to be harvested, both downy and powdery mildew are widespread.
University of Georgia (UGA) Cooperative Extension vegetable entomologists describe squash plants that haven’t sprayed yet with 100 whiteflys per leaf.
Cucurbit downy mildew has been reported in multiple locations in Michigan. Michigan cucurbit growers are warned to detect and disk under plants infected with Phytophthora.
📢New reports of Cucurbit Downy Mildew on cucumber🥒, butternut, and pumpkins🎃 in Massachusetts, Pennsylvania, North Carolina, Michigan, Maryland, New York, Tennessee, and Alabama📢 from July 28 to August 9, 2023.
Clade 1 of the downy mildew pathogen has a broad host range among cucurbits, preferring pumpkins, squash and watermelons. Clade 2 isolates infect and cause damage to cucumbers and melons, and are seen in northern Ohio first. As in 2022, the Fulton County outbreak on pumpkins was unusual for the Great Lakes region.
Whiteflies can cause feeding injury issues in vegetables and transmit multiple viruses. These include cucurbit leaf crumple virus, cucurbit yellow stunting disorder virus, cucurbit chlorotic yellow virus, squash vein yellowing virus and tomato yellow leaf curl virus. Vegetables like squash, zucchini, cucumber, and cantaloupe are highly susceptible to these viruses.