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 others such as York, Rome and Nittany with much susceptible bloom, here is a prediction for areas where bloom was first open Apr 5, 2010. The temperature and rainfall data are current through Monday morning, Apr 26. Predicted weather conditions are shown for Apr 26-30. 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 currently reduced through Apr 28 but will increase where late bloom persists to Apr 30. BBS column, tracking the Apr 8 infection, shows that using extended predicted temperatures, the earliest blossom blight symptoms would begin to appear Apr 29. With the past weekend's recorded temperatures, inserting hail injury into the Maryblyt model for yesterday indicates that infection could have yesterday and an immediate streptomycin application would be suggested for such areas. 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. 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:
A scab and rust infection period in progress. Cedar-apple rust gall spore horns are fully extended. There is a surprising amount of bloom remaining, especially on York, Rome Beauty and Nittany cultivars. These blossoms are probably susceptible to quince rust as well as fire blight.
