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. Susceptible bloom is
open on all cultivars. Here is the prediction for trees where first bloom was open
Monday, April 11, 2016. The temperature and rainfall data are current through
Friday morning, April 22. Predicted weather conditions are shown for April 22-26.
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). For
infection to be predicted, wetting must occur after the EIP (epiphytic
infection potential) reaches 100 or higher, which has been true since Apr 18.
Based on predicted temperatures, the risk column shows infection conditions for Apr 21-24 and Apr 26 and only wetting is lacking for Apr 25. In situations where all other requirements for infection have been met except wetting, wetting from a maintenance spray application can provide the wetting trigger for infection to occur. In high-risk situations, a protective streptomycin application is recommended ahead of predicted infection. A streptomycin spray remains effective about 3 days in warmer conditions when it is needed most and can provide about one day after-infection suppression.
Based on predicted temperatures, the risk column shows infection conditions for Apr 21-24 and Apr 26 and only wetting is lacking for Apr 25. In situations where all other requirements for infection have been met except wetting, wetting from a maintenance spray application can provide the wetting trigger for infection to occur. In high-risk situations, a protective streptomycin application is recommended ahead of predicted infection. A streptomycin spray remains effective about 3 days in warmer conditions when it is needed most and can provide about one day after-infection suppression.
The BBS column
is tracking predicted symptom development for the first infection Apr 21. The
CBS column indicates progression toward the appearance of canker margin
symptoms due to extension of overwintering cankers from last year, which are
predicted to occur when that value reaches 100 Apr 26. Canker advancement
cannot be prevented by chemical treatment at this time and the presence of
symptoms will signal build-up of inoculum which could become a factor in the
event of a trauma blight situation due to hail injury, etc.
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. Be aware that risk can change quickly with unpredicted warmer temperatures and wetting. In high-risk situations, a protective streptomycin application is recommended ahead of predicted infection. The fire blight outlook will be updated Monday, Apr 25.
