By Guy K. Ames, NCAT Horticulture Specialist
In Northwest Arkansas I’m seeing peach leaf curl in my orchard. It’s April, but the calendar date is not as important as the growth stage of the peaches. The professionals call this time “shuck split.” The “shuck,” or the last remnant of the flower, is splitting and falling from the growing young fruit. This is a crucial time for the developing fruit as it is growing rapidly, and this is not a good time for the tree to be stressed. This disease, incited by the fungus Taphrina deformans, causes the leaf to deform and swell irregularly (see photo). As you can imagine, leaf function—primarily photosynthesis and respiration—suffers and the tree is stressed. The more severe the curl (the more leaves are affected), the more stressful it is to the tree.
Managing Peach Leaf Curl
You’re going to want to do something about it, but there’s not much you can do once you see it on your trees other than to remember to spray next year during dormancy. Here’s why. The fungus overwinters in the tiny crevices around the leaf scale (or leaf bud). As soon as the leaf bud begins to swell in the early spring the fungus invades the leaf tissue. That’s right, the fungus is inside the leaf and thus protected from normal fungicide sprays! You should apply sprays of lime-sulfur (the best organic fungicide for this disease) sometime in March before the leaf buds begin to swell. If the trees have gone through severe infection, you can apply once in November when the leaves have fallen and then again in the spring before the new leaves emerge.
Helping an Infected Tree
A tree with a severe infection will sometimes drop all its infected leaves and try to push a new crop of leaves. This is understandably stressful for the tree, so if it happens, the grower could help the tree out by applying a quick release fertilizer of some sort. Organic growers could choose compost tea or fish emulsion. If the infection wasn’t severe (only a small percentage of leaves were infected), then you may need to do nothing. There is only the single infection period, so newly emerging leaves will be safe from T. deformans.
There are a few somewhat resistant varieties, including Clayton, Candor, and Frost, but this resistance is only relative to other more susceptible varieties and often can’t be relied upon for control.
Here’s hoping your leaves aren’t curly!
For more on peach diseases, see the ATTRA Sustainable Agriculture publications Peach Diseases Identification Sheet and Peaches: Organic and Low-Spray Production.
Contact Guy and NCAT’s other agriculture specialists by emailing firstname.lastname@example.org or calling 800-346-9140.