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. Although early cultivars are approaching pink with occasional blossoms open, with warmer temperatures, more bloom will be open later today. With warm temperatures and evening rain predicted for today, I ran Maryblyt as an indication of risk in locations where some bloom (including pollinizer crabapples) is open this morning April 11, 2011. The temperature and rainfall data are current through Sunday evening, April 10. Predicted weather conditions are shown for April 11-12. The components of fire blight risk are indicated in the columns labeled BHWTR with 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). Based on predicted temperatures and wetting, The risk column shows that fire blight infection (I) is possible with predicted rain tonight, April 11 (note red color). For infection to be predicted, wetting has to occur after the EIP (epiphytic infection potential) reaches 100 or higher. Briefly put, bloom that is open today is at risk for infection if wetting occurs tonight. A streptomycin application is recommended for high risk situations. Today’s forecast represents a high risk situation for areas farther south and east of the Blue Ridge with much bloom open, in some cases for a week. For the Winchester area, the current longer-range outlook indicates cool temperatures April 12-19, so risk will subside after today. This graphic will be updated April 13. The BBS and CBS columns are tracking predicted blossom blight symptom and canker blight symptom appearance, respectively. 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.
