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Developing a Management Program for Powdery Mildew in Winter Squashes with Resistant Varieties 2002

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Project Leader(s): Meg McGrath, Dept. of Plant Pathology, Cornell University, Riverhead


Nina Shishkoff, Dept. of Plant Pathology, Cornell University, Riverhead

Alan Erb, Vegetable Specialist, CCE Lake Plains Vegetable Program

Ted Blomgren, Vegetable Specialist, CCE Capital District Vegetable Program

Julie Kikkert, Vegetable Specialist, CCE Ontario-Wayne-Yates Counties

Joseph Sieczka, Dept. of Fruit & Vegetable Science, Cornell University, Riverhead

Dale Moyer, Vegetable/Potato Specialist, CCE Suffolk County

Molly Kyle Jahn, Dept. of Plant Breeding, Cornell University, Ithaca

Bill Johnson, plant breeder, Seminis Vegetable Seeds, California

Type of grant: Pest-resistant crops

Project location(s): National application


Powdery mildew an important disease of winter squash and other cucurbit crops. It occurs throughout New York every year. Management is needed to avoid a reduction in yield. Application of fungicides has been the main practice. Several winter squash varieties with resistance to powdery mildew are now commercially available. Growers need to know how well these resistant varieties perform compared to horticulturally-similar, fungicide-treated susceptible varieties, and whether there are benefits to an integrated program with minimal fungicide inputs. Two experiments were conducted to evaluate acorn and butternut squashes. Growing varieties with resistance to powdery mildew was shown to be an effective and economic means to manage powdery mildew. Control of powdery mildew obtained with the resistant varieties was not improved significantly by applying fungicides. Although also not significant, there was a trend toward improved yield with fungicide treatment (more fruit, greater fruit weight, and higher sucrose content). Regardless of disease control benefit, an integrated program is recommended to reduce selection pressure for new races of the pathogen able to overcome the resistance in these varieties and for new strains of the pathogen that are able to tolerate the fungicides. A reduced-sprays fungicide program with a 14-day spray interval was as effective as the conventional program with a 7-day interval when applied to a resistant variety but not when applied to a susceptible variety.

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