Wednesday, June 11, 2008
I found fire blight today in a block of 1st leaf Golden Delicious apples. (See more pictures.) Not unexpected, these trees had quite a profuse bloom. I suspect they were in bloom during the last week in May, which saw an increased -- in fact, threatening -- risk of fire blight. Of course existing apples were already mostly past bloom, with the exception of some cider varieties, so they were immune. But 1st leaf trees often get planted a little late, take a while to break bud and bloom, and can be in bloom when the weather conditions that favor fire blight are more likely. Thus, my recommendation is to plant as early as possible, apply copper after planting, de-bloom the trees, or make sure to apply streptomycin sprays as the trees bloom and weather indicates a high risk of fire blight infection. You do not want to get fire blight in a 1st leaf orchard on dwarf rootstocks! See F-133 An Annual Fire Blight Management Program for more information. But, in a nutshell for this grower, I would recommend first pruning out all the visible strikes (on a dry day), and maybe treating with a lower rate of copper once or twice. (Cuprofix MZ Disperss from Cerexagri-Nisso would be a good choice, it contains both copper and mancozeb.) Good luck.