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 14, 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 Thursday evening, April 13. Predicted weather
conditions are shown for April 14-20. 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
and possible infection with any wetting Apr 11-12, and
with slightly warmer than predicted temperatures and wetting Apr 13-14 and 17-19.
Infection is predicted with wetting Apr 16. 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 Monday, Apr 17.
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 12-14, and “high”
Apr 15-19. (EIP in Cougarblight lacks only one unit for Apr 16, which would move
the risk to “extreme” for 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 14, 2017. Click to enlarge. |
