VT Apple IPM: Increasing fire blight risk, scab risk is low for now

We are expecting a slight warmup later this week that may push levels of fire blight bacteria high enough to be concerned about infection in blooming orchards. While this event does not look like a ‘high alert’ scenario, and chance of rain is relatively low but still there for Friday, all growers with trees in bloom should keep an eye on NEWA and be ready to treat orchards with open blossoms with streptomycin ahead of an infection period. Apple scab continues to look like a non-issue for as far as the forecast goes, but be prepared to be fully covered before the next significant rain event. NEWA is not suggesting that the low-likelihood, short duration rain that might come tomorrow Friday May 12 will be enough to cause an apple scab infection period. My take- hold off on spraying unless you are in a high fire blight risk situation and you get wetting tomorrow, then apply strep. There’s no need for fungicide at this time but we’re just getting into the season with plenty of spores left to discharge due to the dry weather. The next good rain will likely result in a big infection period and, with the rapid growth we’re seeing at this time of the year, you want your spray coverage as close to the infection period as possible to ensure that new growth is covered.

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