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: Here is a cropped graphic from the Maryblyt 7 program. With early cultivars near full bloom and nearly all with some bloom now open, here is a prediction for trees with first bloom open Monday, April 5, 2010. The temperature and rainfall data are current through Thursday morning, April 8. Predicted weather conditions are shown for April 8-12. 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 predicted thunderstorms this afternoon and evening. For infection to be predicted, wetting has to occur after the EIP (epiphytic infection potential) reaches 100 or higher. Note that this level has reached more than 4X that threshold. Any unprotected block that had blossoms open yesterday is at risk for infection if wetting occurs today. The current longer-range outlook indicates cooler temperatures April 9-10, followed by warming again April 11-12. 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.
