We are seeing quite a bit of peach leaf curl in Southeast Nebraska. Peach leaf curl is caused by the fungus Taphrina deformans. This fungal disease is one of the most common diseases in the home orchard and can affect the blossoms, fruit, leaves, and shoots of peaches and nectarines. (Cherries have a similar leaf curl diseases caused by T. cerasi.) Peach leaf curl is more severe following cool, wet springs; temperatures between 50 and 70 degrees F are ideal for infection.
The primary symptom is a thickened, puckered area on leaves which will turn yellow to red or purple with the loss of chlorophyll. These leaves may prematurely drop, weakening the tree and making it more susceptible to other diseases, pests, and cold injury. The disease can also result in reduced fruit set, size, and quality.
A single fungicide spray applied while trees are still dormant (just prior to bud swell), thoroughly covering all branches, shoots, and buds will control peach leaf curl. Effective controls include Bravo, Ziram, and copper compounds. See the Midwest Fruit Pest Management Guide for details.
At this time of year, most infection has already occurred, and fungicide sprays are relatively ineffective. Fruit on defoliated trees should be thinned to reduce stress and improve tree survival.