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 12, 2017. Click to enlarge. |
FIRE BLIGHT: Above is a cropped graphic from the Maryblyt 7 program, using Apr
5 as the date of first bloom open on Idared cultivar. Early cultivars are near
full bloom and most cultivars have some bloom open. The temperature and
rainfall data are current through Tuesday evening, April 11. Predicted weather
conditions are shown for April 12-17. 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 forecasted
temperatures and wetting, the risk column shows high
risk and possible infection and possible infection with any wetting Apr 11-12, and with slightly warmer than predicted temperatures and wetting
Apr 13-14. Based on cooler predicted temperatures later in the week, risk will
subside Apr 14-15, but will again increase with warmer temperatures Apr 16-17.
Be aware that in situations where all other requirements for infection have
been met except wetting, wetting from any spray application can provide the
wetting trigger for infection to occur, and including streptomycin is suggested
in such situations. In high-risk situations, a protective streptomycin
application is recommended ahead of predicted infection.
Be aware that risk can change
quickly with unpredicted warmer temperatures and wetting. The fire blight
outlook will be updated Friday, Apr 14.
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 remains extreme through Apr 11-13, then subsides
to high Apr 14 and low Apr 15, but returns to high Apr 16. Comparable EIP values
and trends are shown for both predictive programs each day this week.
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| Cougarblight graphic for Winchester, Apr 12, 2017. Click to enlarge. |
