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 but late cultivars (Even Rome Beauty clusters are waking up!), and earlier
cultivars are approaching full bloom. Here is the prediction for trees with
first bloom open Monday, April 11, 2016. The temperature and rainfall data are
current through Monday morning, April 18. Predicted weather conditions are
shown for April 18-23. 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 18-22, with only wetting lacking
as the trigger for fire blight infection these days. Infection is indicated with
predicted showers for Apr 22. Be aware that in situations where all other
requirements for infection have been met except wetting (Apr 18-22), 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 Wednesday, Apr 20.
