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Seasonal Infection of Nonwounded Peach Bark by Botryosphaeria dothidea. P. Lawrence Pusey, research plant pathologist, USDA-ARS, Southeastern Fruit and Tree Nut Research Laboratory, P.O. Box 87, Byron, GA 31008, Present address: USDA-ARS, Tree Fruit Research Laboratory, 1104 N. Western Avenue, Wenatchee, WA 98001; Paul F. Bertrand, professor of plant pathology, The University of Georgia, Georgia Cooperative Extension Service, Tifton, GA 31794. Phytopathology 83:825-829. Accepted for publication 14 April 1993. 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, 1993. DOI: 10.1094/Phyto-83-825.

Conidial suspensions of Botryosphearia dothidea were applied at various concentrations to the nonwounded stems of 1-yr-old peach trees maintained under wet conditions for periods that varied. Bark necrosis increased with spore concentration and the duration of bark wetness. Similar inoculations made at 3-wk intervals during 1987 and 1989 revealed that infection occurred from March through August with a peak period from about late April through July or early August. A significant correlation was found between disease severity and temperature for a 3- to 6-wk period after inoculation. In two commercial orchards, stems of newly planted peach trees were periodically exposed to natural inoculum of B. dothidea. At 1-mo intervals from April 1988 through December 1989, water-excluding covers were removed from preselected trees for a 1-mo period. Infections occurred more frequently in the second season of growth (particularly during June and July) than in the season after planting. Disease severity was positively correlated with the availability of waterborne spores of B. dothidea. Nonwounded bark of 1- to 2-yr-old peach trees is susceptible to invasion by B. dothidea during most of, if not the entire, growing season. The amount of infection during this period depends on inoculum availability and environmental conditions.