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 with first bloom open
Monday, April 11, 2016. The temperature and rainfall data are current through Wednesday
afternoon, April 20. Predicted weather conditions are shown for April 21-25.
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 occurring
today, Apr 18. Based on predicted temperatures, the risk column shows high risk
for Apr 18-23 and Apr 25. Infection is indicated with predicted thunderstorms Apr
23. Be aware that in situations where all other requirements for infection have
been met except wetting (Apr 18-22 and 25), 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.
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 Friday, Apr 24.
