Fire blight update

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. Early cultivars have a lot of bloom open, others are at full pink, and more bloom will open gradually over the next two days. The temperature and rainfall data are current through Thursday evening, April 14. Predicted weather conditions are shown for April 15-22. 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 risk of fire blight infection will be low or moderate through Apr 19, but will again reach an infective level with warmer temperatures and rainfall Apr 20-21 (note red color). For infection to be predicted, wetting must occur after the EIP (epiphytic infection potential) reaches 100 or higher. In high-risk situations, a protective streptomycin application is recommended ahead of predicted infection. This graphic will be updated April 18, or sooner if significant change warrants it. The BBS and CBS columns are tracking predicted blossom blight symptom (from infection Apr 11) and canker blight symptom appearance, respectively. The numbers in these columns represent percent of required degree hours for symptom appearance.

 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.