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 most
cultivars. Here is the prediction for trees with first bloom open Monday, April
11, 2016. The temperature and rainfall data are current through Friday afternoon,
April 15. Predicted weather conditions are shown for April 16-22. 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). For infection to be predicted, wetting must occur after the EIP
(epiphytic infection potential) reaches 100 or higher, which is predicted to
occur Apr 18. Based on predicted temperatures, the risk column shows high risk
for Apr 18 and Apr 20-22, and only wetting is lacking as a trigger for
fire blight infection those days. Be aware that in such situations, the wetting by a maintenance spray application can meet the wetting requirement for infection to
occur when the EIP is above 100 and all other requirements for infection have
been met. In high-risk situations, a protective streptomycin application is
recommended ahead of predicted infection.
The CBS column at the right in the graphic indicates progression toward the appearance of canker margin symptoms due to extension of overwintering cankers from last year, which would be predicted to occur when that value reaches 100. 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 WeatherChannel 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 18.
