CAUTION: The observations, conditions, and recommendations reported for Winchester, VA are provided as a guide to fire blight risk assessment only for the immediate area of the Virginia Tech AREC located six miles southwest of Winchester. Use of the information reported here for making orchard management decisions outside of that area is not our intent. Fruit producers outside of that area are encouraged to consult their state extension specialists for information similar to that provided here.
FIRE BLIGHT: Above is a cropped graphic from the Maryblyt 7 program. With early cultivars with bloom open, and more bloom opening over the next several days, here is a prediction for apple orchards with first bloom open Friday, April 17, 2015. The temperature and rainfall data are current through Friday afternoon, April 17. Predicted weather conditions are shown for April 18-22. 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 if wetting occurs Monday, Apr 20. For infection to be predicted, wetting must occur after the EIP (epiphytic infection potential) reaches 100 or higher. Infection is more likely in areas where bloom is more advanced, and temperatures warmer than those shown for Apr 17-21. In high-risk situations, a protective streptomycin application is recommended ahead of predicted infection. Following this high risk period, predicted cooler temperatures should reduce risk Apr 22 and 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. Be aware that risk can change quickly with unpredicted warmer temperatures and wetting.
