High fire blight risk April 11-13!

NOTE: This year for fire blight risk assessment, we are comparing and posting 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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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 approaching full bloom and later ones are at open cluster or pink and will come into bloom in the next two days. The temperature and rainfall data are current through Monday morning, April 10. Predicted weather conditions are shown for April 10-15. 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 for Apr 11-13, and possible infection with any wetting Apr 11-12, and with slightly warmer than predicted temperatures Apr 13. Based on cooler predicted temperatures later in the week, risk will subside Apr 14-15, but will again increase with warmer temperatures Apr 16. Be aware that in situations where all other requirements for infection have been met except wetting, wetting from a maintenance spray application can provide the wetting trigger for infection to occur and routinely 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 Apr 12.

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" through Apr 11-13, then subsides to low Apr 15. Comparable EIP values and trends are shown for both predictive programs each day this week. 

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