Early Season Grape IPMThe season has gotten off to a slow start due to cool weather across the region but once it warms up you can expect the shoots to grow very quickly.
If shoots are out and in a holding pattern, beware of damage by grape flea beetle (also called steely beetle). While considered a nuisance pest, if large numbers are present it can cause quite a bit of bud damage and exacerbate any winter bud injury problem. A NY IPM flea beetle fact sheet and information from the NY-PA Pest Management Guidelines for Grapes will help guide your management decisions. Dr. Greg Loeb, entomologist at Cornell University recommends treatment of flea beetle and climbing cutworm if damage to bud and shoots exceeds two percent.
In their recent newsletters, Dr. Mike Ellis (Ohio State Univ) and Dr. Wayne Wilcox (via Alice Wise, Cornell University) recommend early season fungicide applications for phomopsis at shoot length of 3” or less, especially if there is a lot of rain. Current dry weather will help suppress phomopsis, but continue to scout blocks with a history of phomopsis problems.
In trials early season sprays have reduced later cluster infections, where rachis infections can spread to the berry stem and then to berries. Dr. Ellis says that control of the four major fungal diseases (phomopsis, powdery mildew, downy mildew and black rot) benefit from early season applications. At a temperature threshold of 50F both downy mildew and powdery mildew need very little rainfall moisture to get established on new shoots. Because rapid shoot growth is expected once the warm weather arrives, growers should be ready with their pre-bloom through post-bloom treatments, the most critical period for control according to Dr. Ellis.
In the April 30 Ohio Grape Electronic Newsletter Dr. Ellis writes extensively about the identification and avoidance of fungicide resistance (especially powdery mildew and downy mildew), something ALL commercial grape growers need to understand and practice – Table 2 includes resistance prone fungicides and risk of resistance by chemical class. He also discusses critical periods for fungicide applications and offers his complete suggested guidelines for developing a fungicide spray program for grapes grown in Ohio, from dormant applications to a fourth post-bloom application.
I would like to thank Dave Scurlock and Mike Ellis, Wayne Wilcox and Alice Wise, and Hans Walter-Peterson for providing much of this information. [Editor’s note: See Mark Chien’s newsletter for subscription information regarding the above author’s respective newsletters.]
May 4, 2013
Wine Grape Information for the Region, May 4 – Abridged
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