Fire blight caution

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 trees with first bloom open yesterday, April 20, 2014. The temperature and rainfall data are current through this evening, April 21. Predicted weather conditions are shown for April 22-26. 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 high. For infection to be predicted, wetting must occur after the EIP (epiphytic infection potential) reaches 100 or higher.  Infection would be more likely in areas where bloom is more advanced, and temperatures are a couple degrees warmer than that shown for Apr 25 or 26, and if wetting occurs Apr 25-26. In high-risk situations, a protective streptomycin application is recommended ahead of predicted infection. 

This graphic will be updated April 23, 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.