NOTE: This year for fire
blight risk assessment, we are comparing graphics from Maryblyt 7 as in previous years,
and also from the Cougarblight model as shown on our NEWA site. We are using the same
weather data from our NEWA station to make these
comparisons.
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.
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| Maryblyt graphic for Winchester, Apr 19, 2017. Click to enlarge. |
FIRE BLIGHT: Above is a cropped graphic from the Maryblyt 7 program, using Apr
5 as the date for first bloom open on Idared cultivar. Early-blooming cultivars still have much susceptible bloom, and later cultivars such as Rome Beauty are near full bloom in the Winchester area. The temperature and rainfall data are
current through Tuesday evening, April 18. Predicted weather conditions are
shown for April 19-24. 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. Based on recorded temperatures and wetting, the risk
column shows high risk and possible infection with any wetting
Apr 11-12, 15-18 and 21, and with slightly warmer than predicted temperatures
and wetting Apr 13-14 and 20. Infection was indicated for Apr 12, and 15-18 and
is predicted with wetting Apr 21. Note 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.
Predicted cooler temperatures should
reduce risk Apr 19-20 and 22-24, but will probably cause late bloom to persist
into next week. Continue to protect late bloom as
needed. The fire blight outlook will be updated Friday, Apr 21.
Below is the graphic
from the Cougarblight model as shown on our NEWA site. Note that we selected
orchard blight history option as “Fire blight occurred in your neighborhood
last year” and first blossom open date as 4/5/2017. (This date must be re-set
each time this site is accessed). Cougarblight shows color-coded risk
assessment as “Cougarblight 4-Day DH” which is “extreme” Apr 17-18, and “high”
Apr 19-23. Both predictive programs indicate a reduction in fire blight risk
after Apr 18, but EIP values are somewhat higher in Maryblyt than for
Cougarblight.
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| Cougarblight graphic for Winchester, Apr 19, 2017. Click to enlarge. |
