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Role of Conidia of Botryosphaeria dothidea in the Natural Spread of Peach Tree Gummosis. D. J. Weaver, Research plant pathologist, U.S. Department of Agriculture, Science and Education Administration, Federal Research, Southeastern Fruit and Tree Nut Laboratory, P.O. Box 87, Byron, GA 31008; Phytopathology 69:330-334. Accepted for publication 25 October 1978. This article is in the public domain and not copyrightable. It may be freely reprinted with customary crediting of the source. The American Phytopathological Society, 1979. DOI: 10.1094/Phyto-69-330.

Symptoms of peach (Prunus persica) tree gummosis were visible 913 mo after healthy limbs were exposed for 30-day periods to conidia of Botryosphaeria dothidea produced on naturally infected peach wood. Experimental inoculations in July caused significantly more infections than those in March, April, or May. Branches inoculated in June with a suspension of conidia had symptoms after only 3 mo. Swollen lenticels and sunken lesions developed on 1 or 2 yr old branches; only sunken lesions formed on 3 yr old branches. Conidia were first detected in rainwater traps on 22 March, and the greatest numbers were collected in late July and early August 1977. Numbers of conidia declined in December and none were detected in rainwater after 30 December. The rainwater collection from limbs diseased for 12 yr yielded from 2 to 138 times as many conidia as limbs diseased for 45 yr. The optimum temperatures for germination and germ-tube growth of conidia obtained from diseased wood or agar cultures were 2535 C and 30 C, respectively. Warm wet weather favored the release and germination of conidia that infected peach bark through lenticles and induced gummosis symptoms.

Additional keywords: lenticels, Prunus persica.