FIRE BLIGHT: Below is the updated graphic from the Maryblyt 7 program. Based on 9-day predicted temperatures and wetting, the risk column shows the fire blight infection risk history through Apr 30 and predicted risk through May 9. The next four days, May 1-4, illustrate that the EIP (epiphytic infection potential) can gradually increase although the average daily temperature is lower than the of 60°F required minumum for infection to occur. This is because the EIP is based on estimated degree hours that the temperature is above 65°F throughout the day. Based on predicted temperatures, the EIP will approach the required threshold of 100 later next week (97% on May 9). Most cultivars are still near full bloom and some susceptible bloom will likely be present and should be protected if those conditions occur. The CBS column at the right in the graphic indicates progression toward the appearance of canker blight symptoms on new growth, due to extension of overwintering cankers from last year, with canker margin symptoms (CMS) by May 8. Canker advancement will not be prevented by a chemical treatment and the presence of symptoms will indicate a build-up of inoculum which could become a factor in the event of a trauma blight situation due to hail injury, etc.
CAUTION: As usual, be aware that risks can change quickly with unpredicted warmer temperatures and wetting. In high-risk situations, a protective streptomycin application is recommended ahead of predicted infection. The weather conditions used in the predictive part of this graphic come from the Weather Channel for Winchester, supplemented by site-specific data from SkyBit Inc.
