Thunderstorms are forecast in many areas across the province overnight tonight and into Thursday morning. With the hot temperatures, infection risk is extreme according to the Ontario fire blight prediction maps. Any blocks with secondary or late bloom could be in for significant infection if these blooms are not protected. If applying an antibiotic, keep in mind the preharvest intervals for Streptomycin and Kasumin are 50 and 90 days, respectively.
The unsettled weather may also bring hail, strong winds or heavy rains that could trigger trauma blight. These could be very isolated events, occurring in one area but not another nearby. Assess for signs of damage in all blocks following any storm. Winds and rain can spread inoculum while injuries caused by these events provide an entrance for the pathogen and shock or traumatize trees, reducing their natural defense mechanisms. Shoot or fruit blight can develop as a result.
Be sure to apply Streptomycin or copper as soon as possible after the trauma event, especially if foliage damage is extensive or fire blight is known to be active in the orchard (ie., cankers, etc). New research is now suggesting ideal timing is 4 to 12 hours after a storm. Anything applied later runs the risk that the bacteria will have already established and begun to grow, reducing the efficacy of the product.
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