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Using Apple Scab Pseudothecial Squash Mounts for Timing Early Scab Sprays 2001

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Project Leader(s): David A. Rosenberger, Cornell’s Hudson Valley Laboratory, Highland, NY

Cooperator(s): Deborah Breth, Lake Ontario Fruit Team

Kevin Iungerman, Northeastern NY Fruit Program

Mike Fargione, Hudson Valley Fruit Program

Type of grant: Monitoring, forecasting, and economic threshold

Project location(s): All of NY and portions of New England

Abstract: Apple scab is the most important disease of apples in New York State where apples are grown on more than 50,000 acres. Apple growers control apple scab by applying fungicides to prevent infections on leaves and fruit. Growers can avoid unnecessary fungicide sprays if they know when the apple scab ascospores in the over-wintering leaf litter will be released. Eliminating one fungicide spray on all of the apple acreage in New York would save growers approximately $1.2 million each year, but eliminating a spray when it is really needed could cause losses equal to at least four times that potential savings. In a project funded by the New York State IPM program, samples of apple leaf litter from seven locations around New York State were assessed at critical times during spring to determine the status of apple scab ascospore maturation and release. Each of the 18 assessments involved detailed microscopic examinations of the fungal spore-producing structures after they had been removed from the leaf litter. The lead scientist provided results to extension educators who then used e-mail, code-a-phones, faxes, radio spots, and newsletters to inform apple growers about results of scab spore assessments. The scab spore assessments helped apple growers recognize that spores were available for discharge unusually early in the 2001 growing season. As a result, growers were advised to be especially careful about protecting trees during the very earliest stages of tree growth so as to avoid infections that, if allowed to occur, would have necessitated extra fungicide sprays throughout summer. This cooperative effort between scientists and Cooperative Extension field staff contributes to the profitability of the New York apple industry.