Symptom Identification and Control Methods for Peach Leaf Curl

Peach leaf curl is a common disease in spring, mainly affecting ornamental peach, cherry, apricot, plum and others.

1. Pathogen: The disease is caused by fungi of the class Taphrinomycetes in the phylum Ascomycota.

2. Symptoms: It mainly affects leaves, and in severe cases can also affect flowers, young fruit and tender shoots. After leafing out in spring, infected plants show shrivelled, rippled leaves with the leaf tip and margins curling backwards and the leaf surface uneven. As the leaves grow, the leaf colour gradually changes from yellow-green to purplish-red, the mesophyll thickens and becomes brittle, and the unevenness increases. In late spring and early summer, a layer of white powder forms on the leaf surface, and soon afterwards the diseased leaves turn black, wither and drop off; infected tender shoots become shortened and swollen, grey-green or yellow, with leaves clustered on the diseased shoots, and in severe cases the shoots die; diseased fruit develops abnormally, with the fruit surface cracking and the fruit fuzz falling off, though the surface remains smooth.

3. Disease characteristics: The pathogen overwinters as ascospores or blastospores in the crevices of bud scales or on the bark. When peach buds sprout the following spring, the blastospores produce germ tubes that penetrate the epidermis directly or enter the tender leaves through the stomata. The ascospores and blastospores produced by the diseased leaves of that year mature in late spring and early summer. The disease occurs severely in April and May and spreads by wind, but because the temperature is high at that time, it generally does not infect again; infection occurs only once a year, and as the temperature rises the disease stops developing, with no occurrence once the temperature exceeds 30°C. Low temperatures and abundant rain in spring favour the occurrence of this disease, and it is also common along riverbanks, beside lakes and in low-lying land.

4. Control methods:

① In late autumn or early spring, promptly prune out diseased branches and leaves and clear away diseased plant debris, or pick off diseased leaves early before the white powdery layer forms on their surface, so as to reduce the source of the pathogen;

② In early spring, when the peach buds are swelling but have not yet leafed out, spray with 4-5 degrees Baumé lime sulfur mixture;

③ Spraying 0.1% copper sulfate solution before leafing out can also provide effective control.