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IPM Message for Cranberry Growers: Jul 7, 2010

Jul 7, 2010

If you are planning to spray for weevils, you should do so soon. Scout, assess, and treat; don’t wait. Reports of cranberry fruitworm pressure (in terms of unhatched, viable eggs) has been variable; some high numbers and some low. Try to use a magnifier when inspecting the calyx end of the fruit for unhatched viable eggs. The eggs are very difficult to see with your naked eye and it is easy to make a mistake and this will directly impact your spray decision. The biggest issue now is the prolonged heat and the stress that it is placing on the vines. Make sure you keep the vines well watered during this period until the heat breaks. Weather forecasts indicate these high temperatures could last for at least another week. We should hopefully get out of the 90’s but high 80’s will continue to predominate.

If you are considering a Callisto application, weigh the benefits vs the risks at this time. Vines under stress may not metabolize the herbicide as well as normal vines and injury may occur. If you have a lot of dodder or heavy weed pressure, it may be worth the risk of vine injury to spray now. If the hot weather persists for a long string of days, you may just need to pick the best “worst” day and go for it. However, if you don’t have to spray, wait for a break in the weather.