Earlier this spring, a friend from Fallbrook was visiting and he mentioned that his peach tree had had a lot of leaf curl last year but this year there was no infection. “I finally got the spraying right!” he said.
Slowly, I said, “Those results might not be just because of your spraying. I don’t want to burst your bubble but I’ve never sprayed any of my peach or nectarine trees and they don’t have any leaf curl this year either.”
(See that photo above? That’s the only leaf I could find in my yard that showed any infection today. There had been a few more leaves infected on a couple of varieties that I’d noticed last month, but they must have since dropped.)
“Remember the weather last spring?” I asked. “I don’t know exactly about your place, but here in Ramona we got six inches of rain in March, and then we got another six inches of rain in April. We never get that much rain that late in the spring. Wet spring weather when the peach trees are leafing out is exactly what the fungus that causes leaf curl needs to thrive.”
“OK,” he said.
“But think about how dry it’s been this spring by comparison. There hasn’t been any real rain since a little storm or two in early March, and February didn’t even have any rain.”
“I think it’s all about the weather, at least for my trees,” I continued. “If the spring is wet, they get leaf curl. If the spring is dry, they don’t. That’s what I’ve noticed on my trees and others that I see when I drive around. Not to say that you’re spraying didn’t do anything, but it’s possible that even if you hadn’t sprayed at all this year you wouldn’t have seen much leaf curl just because of the weather.”
Weather conditions that help or hinder peach leaf curl
Can we get any more specific about the weather conditions that Taphrina deformans, the fungus that causes peach leaf curl, likes or doesn’t like? I can’t. But researchers at the University of California do:
“Wetness from rain, dew, or irrigation for more than 12.5 hours at temperatures below 61°F is needed for infection. Maximum infection occurs when trees are wet for 2 or more days. . . Development of peach leaf curl ceases when young tissue is no longer developing or when weather turns dry and warmer (79° to 87°F).”
What should we do with this information?
It’s helpful to understand better why our trees look the way they do and vary in appearance from year to year. This year, spring has been dry and warm, and at least here is one upside to this weather.
If you’re interested in trying to fight peach leaf curl during cool, wet springs, see my post, “Dormant spray deciduous fruit trees?”
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