NOTE: Over the next couple days, apples will be near the peak of bloom in the Winchester area. Below are the fire blight risk assessments, comparing graphics from Maryblyt and also from the Cougarblight model as shown on our NEWA site, 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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| Graphic from Maryblyt 7, May 2, 2018. Click to enlarge. |
FIRE BLIGHT: Above is a cropped graphic from the Maryblyt 7 program, with first bloom open Apr 14. The temperature and rainfall data are current through Wednesday evening, May 2. Predicted weather conditions are shown for May 3-8. 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, dew or a spray application), 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, and this must coincide with an average daily temperature of 60°F or more. Based on recorded temperatures and wetting, the risk column shows high risk for May 2-4 and May 7-8. With a forecast for rain during the weekend, infection conditions are shown for May 5-6, and only the wetting requirement is lacking for May 3-4 and May 8. Because a spray application can serve as the wetting trigger, include streptomycin with any spray application May 3-8. Streptomycin remains effective for only about three days under these conditions, so the ideal application timing for protection through the weekend would be May 4. Remember to protect young and recently planted trees, with flowers but considered to be "non-bearing".
Below is the graphic from the Cougarblight model as shown on our NEWA site. We selected orchard blight history option as “Fire blight occurred in your neighborhood last year” and first blossom open date as 4/14/2017. Cougarblight shows color-coded risk assessment as “Cougarblight 4-Day DH” risk is extreme for May 2-7, and EIP infection conditions are shown for May 3-6.
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| Graphic from Cougarblight, May 2, 2018. Click to enlarge. |
In general, similar fire blight risks prevail throughout areas in Virginia and probably much of the Mid-Atlantic region, wherever susceptible bloom is present, from late bloom in the southern areas, to early bloom in the more northern areas.
Powdery mildew has been very active the past week. Any “dry weather“ day above 53° is suitable for mildew infection. Since Apr 10 we have had 15 mildew infection days at our AREC.
Powdery mildew has been very active the past week. Any “dry weather“ day above 53° is suitable for mildew infection. Since Apr 10 we have had 15 mildew infection days at our AREC.
