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 most cultivars near full bloom and all with some bloom open, here is a prediction for trees with first bloom open Monday, April 5, 2010. The temperature and rainfall data are current through Friday morning, April 9. Predicted weather conditions are shown for April 9-12. 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). The risk column shows that fire blight infection occurred as predicted with storms with strong winds yesterday afternoon. The wind-driven rains made it likely that bacteria would have spread throughout an orchard from blossoms that were open earlier to ones that had opened just before the rain. For infection to be predicted, wetting has to occur after the EIP (epiphytic infection potential) reaches 100 or higher, and this level had reached 4X that threshold. Cooler temperatures will reduce the fire blight threat through the weekend. The Maryblyt graphic will be updated April 12 or earlier if it changes dramatically. 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.
Other diseases:
Yesterday's 10-hr wetting from 4 PM to 2 AM this morning was not quite long for apple scab infection, and cedar-apple rust spores were not released. Predicted dry weather through most of next week will again favor powdery mildew infection.
