FIRE BLIGHT: Above is a cropped graphic from the Maryblyt 7 program. With many cultivars with bloom open, others are at full pink, and more bloom opening gradually over the next several days, here is a prediction for trees with first bloom open Friday, March 23, 2012. The temperature and rainfall data are current through Friday morning, March 30. Predicted weather conditions are shown for March 31-April 3. The components of fire blight risk are indicated in the columns labeled B (blossoms open), H (degree hours for epiphytic bacterial populations), W (wetting by rain or dew), and T (average daily temperature 60 F or above). Based on predicted temperatures and wetting, the risk column shows that risk of fire blight infection will be mostly low or moderate through Apr 3, but higher if wetting occurs with showers Apr 1. For infection to be predicted, wetting must occur after the EIP (epiphytic infection potential) reaches 100 or higher. Note there had been an earlier threat of fire blight on apples at our AREC last weekend, but temperatures fell about 3 degrees cooler than would have been required, based on bloom first open Friday, March 23. For pears which had been in bloom earlier in the week, or apples in areas with bloom open Mar 22, infection would have been possible with wetting Saturday, Mar 24. In high-risk situations, a protective streptomycin application is recommended ahead of predicted infection.
This graphic will be updated April 2, or sooner if significant change warrants it. The weather conditions used in the predictive part of this graphic come from the Weather Channel for Winchester, supplemented by site-specific data from SkyBit Inc.
