“We like Previsto because it generally makes our trees look fairly happy after we’ve applied it,” he said, comparing photos of a leafy, flower tree treated with Previsto and a more scraggly neighbor treated with another form of soluble copper. Just remember, copper chemicals increase the risk of russet, though Previsto and Cueva have additives to mitigate that risk. The effective rate for Previsto is 3 quarts per acre. Previsto (copper hydroxide) or other soluble copper compounds also are good choices. To improve control, mix it with Cueva (copper octanoate). Serenade Opti, a Bacillus-based biorational, applied every two to four days would be the safest for fruit.
SPRAY FOR FIRE BLIGHT ON APPLE TREES FULL
Just remember that pears, especially Anjou and Comice, are more susceptible to russeting than are apples, and the risk from Blossom Protect might be too high, especially in wetter climates.įrom full bloom to petal fall, when the weather is warming up, he recommends watching the Cougar Blight model, a computer-based risk assessment developed by Washington State University Extension, to determine spray intervals. Try to get at least one full application or two half applications and cover every row. He recommends applying Blossom Protect right after the second round of lime sulfur. Lime sulfur kills bacteria, but it also kills yeast. Lime sulfur and Blossom Protect have a tricky dynamic. After early lime sulfur sprays for thinning, make sure to apply Blossom Protect (Aureobasidium pullulans). He has been telling applicators and conventional growers the same thing.Īs for when to start, he recommends applying 5 pounds to 6 pounds per acre of fixed copper just prior to green tip.Įarly during bloom, his research has found that lime sulfur sprays used to thin flowers also suppress fire blight. “So, I’ve been trying to get people to extend their programs, and I think it makes a difference in fire blight control,” he said. In one old Bartlett block, his inoculum count jumped from 200 cells per flower at petal fall to over 1 million cells per flower a week later.Įventually, the tree will reach a point at which sprays will do no good, but researchers are uncertain exactly when that point is. In most of his trials in Corvallis, Oregon, he has found the highest populations a week after petal fall, when flowers are all but gone. In fact, that was one of his main messages: Continue spraying a week past petal fall, especially if temperatures spike. Instead, organic growers must follow a season-long, phenology-based program of copper sprays, lime sulfur and Bacillus-based biorationals that lasts through petal fall, and beyond. And even those that do work may cause russeting in certain varieties. (TJ Mullinax/Good Fruit Grower)įirst, his disclaimer: Antibiotics are not allowed on organic fruit and none of the organic alternatives work as well, he said. Ken Johnson, Oregon State University, speaks during the Organic Controls that Work panel at the Washington State Tree Fruit Association’s annual meeting in December 2018 in Yakima, Washington.
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