BURLINGTON – Peach leaf curl has been a common disease of peach trees this spring in Vermont. The disease often occurs in wet cool springs following mild winters.
The fungus (Taphrina deformans) causes the foliage to become stunted, puckered and deformed with a reddish to purple tinge, often causing alarm in gardeners. Blossoms, fruit and shoots can also be infected and although the disease will not kill the tree, leaf drop can occur, and fruit production can be reduced.
The peach leaf curl fungus causes leaves to become puckered and distorted.
If leaf drop occurs early, the tree may produce a new set of leaves that show no damage. Plum pockets, a similar disease caused by a different Taphrina species, can be seen in plums, but the most obvious symptoms are distorted fruit. Another Taphrina species causes raised blisters on oak leaves in cool wet springs following mild winters.
The fungus overwinters in the bark crevices and bud scales of its hosts. While still in the bud, the fungus infects leaves and shoots just as they begin to emerge, and foliage symptoms appear about two weeks later if temperatures are mild (50 to 70 degrees Fahrenheit), and the weather is wet.
As the fungus grows between the cells in the leaf, it stimulates the cells to divide and expand, causing the leaf to swell and pucker. The pinkish colors are caused by plant pigments that accumulate in the distorted cells.
Close up of peach leaf curl disease showing thickened, distorted pinkish leaves
The fungus produces a fruiting body (like a mushroom only much smaller) that releases spores that are carried to new tissue. The fungus does not infect mature leaves or fruit and remains dormant during the summer.
The disease will not kill the tree but can make it more susceptible to other stresses such as drought or winter injury. Keep up the vigor of the tree by proper pruning to let in air and light and water during times of drought. Thinning the fruit can also help reduce stress to the tree and helps increase the size of the remaining fruit.
There are resistant or tolerant peach varieties, such as “Frost,” “Muir” and “Indian Free,” but these may not be winter hardy enough for Vermont conditions. A fungicide application before the buds swell in the spring will control the disease in commercial orchards but is rarely warranted for backyard trees.
Dr. Ann Hazelrigg is the University of Vermont Extension plant pathologist and director of the UVM Plant Diagnostic Clinic.
