The Schnabel lab at Clemson University is still offering free testing to help identify resistance problems in the gray mold pathogen Botrytis cinerea from small fruits. The test covers the most important FRAC codes for gray mold control. As grapes approach veraison, Botrytis may start to become a problem as clusters tighten and/or in low ventilated areas of the vineyard (see picture). Don’t assume that all of your fungicides in your spray program are effective at controlling Botrytis. In past years, we have discovered that local growers were in fact spraying chemistries that Botrytis was resistant too – this is equivalent to spraying water to control Botrytis (which won’t work).
The viticulture team is encouraging all growers to participate this year to find out what level of resistance or lack there of is occurring in your vineyard so we can get a grasp on what is happening across the state. You would be surprised to find what your neighbor is spraying may be effecting your vineyard in terms of resistance. This test is FREE!!! The link below helps to provide some instruction on collecting botrytis sampling. Your local county Extension Agent should be willing and knowledgeable on collection procedures.
Note: although this shows collection on strawberries, grapes would be the same (swabbing the fruit with q-tips).