The observations, conditions, and recommendations reported for Winchester, VA are provided as a guide to fire blight risk assessment for the area of the Virginia Tech AREC located six miles southwest of Winchester. At our AREC most apple cultivars still have some susceptible bloom and later blooming cultivars, such as Rome Beauty, are at full bloom.
FIRE BLIGHT ALERT: The risk column of Maryblyt 7 graphic below, based on predicted temperatures and wetting for May 8-14, shows that fire blight risk will be extremely high for the next week, lacking only wetting for infection for May 12, and with predicted wetting, infection conditions are likely May 8-11 and 13-14. In high-risk situations, a protective streptomycin application is recommended ahead of predicted infection conditions. Be aware that routine spray applications can provide enough wetting to meet the wetting requirement for infection when all other infection conditions have been met. Under the conditions shown for the next week, streptomycin remains residually effective for only about 3 days.
Above is a graphic from the Maryblyt 7 program. The temperature and rainfall data are current through Wednesday evening, May 7. Predicted weather conditions are shown for May 8-14. The components of fire blight risk are indicated in the columns labeled B (blossoms open), H (degree hours for epiphytic bacterial population buildup, EIP >100), W (wetting by rain or dew), and T (average daily temperature 60 F or above). This graphic will be updated May 9. 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.
