Fire blight and apple scab forecast

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.

(Click picture to enlarge)


FIRE BLIGHT: Above is a cropped graphic from the Maryblyt 7 program. Many cultivars still have much susceptible bloom. Here is a prediction for trees with first bloom open Monday, March 23, 2012. The temperature and rainfall data are current through this morning, Apr 18. Predicted weather conditions are shown for Apr 18-22. 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 could have occurred with any wetting from rain, a spray application, or heavy dew Apr 15-17. After one-day breaks today and Apr 20, risk will again return to an infective level tomorrow, Apr 21-22. In high-risk situations, a protective streptomycin application is recommended ahead of predicted infection and with any spray applications of other materials. Be aware that risks can abruptly increase with unpredicted warmer temperatures and wetting. This graphic will be updated Apr 20. 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.

Also, today's wetting could result in a secondary apple scab infection period if it remains wet into tonight.