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 some apple trees at petal fall but many still with susceptible bloom, here is a prediction for trees with first bloom open Monday, Apr 5, 2010. The temperature and rainfall data are current through Friday morning, Apr 23. Predicted weather conditions are shown for Apr 23-26. 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). The risk column shows that infection could have occurred Apr 16 and Apr 8 (not shown). Risk is reduced through at least Apr 26 as shown, due to cool weather (and actually well into next week with the current forecast). As always, be aware that risks can increase quickly with warmer than predicted temperatures and unpredicted wetting, and protect high-risk blocks through late bloom as needed. BBS column, now tracking the Apr 8 infection, the infection shows that we will have reached 91% of the requirement for predicted blossom blight symptoms by Apr 26; using extended predicted temperatures the BBS column would predict the earliest blossom blight symptoms Apr 29. 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.
