FIRE BLIGHT: Above is a cropped graphic from the Maryblyt 7 program. Many apple trees are now near full bloom or approaching petal fall but with much bloom still open and susceptible. The temperature and wetting data are current through Monday morning, April 25. Predicted weather conditions are shown for April 25-30. 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 fire blight infection is possible with rainfall each day this week through Apr 28 (note red color). For infection to be predicted, wetting must occur after the EIP (epiphytic infection potential) reaches 100 or higher. Although temperatures will decline slightly Apr 29-30, risk will remain at an infective level if wetting occurs. In high-risk situations, a protective streptomycin application is recommended ahead of predicted infection. This graphic will be updated April 27, or sooner if significant change warrants it. The BBS and CBS columns are tracking predicted blossom blight symptom (from infection Apr 11 and later ones as a and c) and canker blight symptom appearance, respectively. Numbers in these columns represent percent of required degree hours for early blossom symptom appearance and canker margin symptoms Apr 26. 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.
