FIRE BLIGHT: Above is a cropped graphic from the Maryblyt 7 program. With many cultivars with bloom open, and more bloom opening gradually over the next several days, here is a prediction for trees with first bloom open Monday, March 23, 2012. The temperature and rainfall data are current through Monday morning, Apr 2. Predicted weather conditions are shown for Apr 2-5. 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 5, and actually for several days beyond that. (It appears that we will be having a prolonged bloom period). 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 Mar 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 Mar 24. In high-risk situations, a protective streptomycin application is recommended ahead of predicted infection. This graphic will be updated later in the week. 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.
