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Using Apple Scab Pseudothecial Squash Mounts for Timing Early Scab Sprays 2002

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


Deborah Breth, Lake Ontario Fruit Team

Kevin Iungerman, Northeastern NY Fruit Program

Mike Fargione, Hudson Valley Fruit Program

Juliet Carroll, NY State Fruit IPM Coordinator

Type of grant: Monitoring, forecasting, and economic thresholds

Project location(s): Results of monitoring were used throughout all of NY and portions of New England.


Apple scab is the most important disease of apples in New York State where apples are grown on more than 44,000 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 million each year. However, 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 eight locations in six counties 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 12 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 although spore maturity lagged tree development in the lower Hudson Valley, mature spores were available for discharge when trees in other regions of the state reached bud burst. As a result, Hudson Valley growers were advised to delay their first spray for at least a week after budbreak whereas growers in other regions were advised to protect trees from apple scab as tree produced green tissue. This cooperative effort between scientists and Cooperative Extension field staff contributes to the profitability of the New York apple industry by eliminating unnecessary fungicide sprays and avoiding losses where omitting fungicides would result in losses to apple scab.

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