Peach, nectarine
Written by:
Dr. Renae Moran
This disease, caused by a fungus, infects leaf buds in spring at bud break. Foliage shows signs of infection later during rapid shoot growth. It is not much of a problem in managed orchards unless fungicide applications are skipped in years with no crop. Fruit infections are uncommon.
Symptoms
Leaf puckering, yellowing and orange discoloration in severe cases are indicative of leaf curl infection. Shoots outgrowth the infection in mild cases, but severely infected shoots might not survive winter. Infected foliage drops in summer.
Disease cycle
Spore dispersal my splashing rain and wind. Spores overwinter on the tree in the cracks and crevices. Spore germination in spring coincides with bud swell through bud opening. Wet weather at this time leads to leaf tissue infection. Leaves that unfold outside the bud are not susceptible to infection, so later in spring and through summer, infections will not occur.
Management
Resistant varieties are an option and should be a consideration for organic or low-spray orchards. Severe infections can weaken trees. Elberta, Harken and Redhaven have partial resistance.
A fungicide application in fall just prior to leaf drop or in spring just prior to bud break. Regular fungicides for other problems will substantially reduce the prevalence of this disease. Fixed coppers, lime sulfur, chlorothalonil and Bordeaux mix are effective fungicides. Once infected, fungicides are not effective at managing this disease. Chlorothalanil is not labeled for use on apple. Copper compounds will also suppress bacterial spot.