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 17, 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. Most cultivars now have
some susceptible bloom open in the Winchester area. The temperature and rainfall data are
current through Sunday evening, April 16. Predicted weather conditions are
shown for April 17-22. 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 and 15-18, and with slightly warmer than predicted temperatures and
wetting Apr 13-14 and 19-20. Infection was indicated for Apr 12, and 15-16 and is predicted with wetting Apr 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.
As indicated with the
changes in prediction for Apr 15-17 since the Apr 14 posting last week, risk
can change quickly with unpredicted warmer temperatures and wetting. Particularly
this week, continue to protect late bloom as needed. The fire blight outlook
will be updated Wednesday, Apr 19.
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 16-18, and “high”
Apr 19-20. Both predictive programs indicate a reduction in fire blight risk
after Apr 18, but EIP values are somewhat higher in Maryblyt than for Cougarblight
and that might be a factor for predicted risk later this week if weather
conditions are more favorable for fire blight than currently predicted for Apr
19-22.
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| Cougarblight graphic for Winchester, Apr 17, 2017. Click to enlarge. |
