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Environmental Factors Affecting Brown-Spot Infection on Longleaf Pine. A. G. Kais, Plant Pathologist, Southern Forest Experiment Station, Forest Service, U.S. Department of Agriculture, Gulfport, Mississippi 39501; Phytopathology 65:1389-1392. Accepted for publication 25 June 1975. DOI: 10.1094/Phyto-65-1389.

Indirect evidence suggested that light enhances infection of Pinus palustris by stimulating the opening of stomata through which the brown-spot fungus Scirrhia acicola penetrates the needles. In the absence of light, the fungus functions primarily as a wound parasite. Exposure of seedlings to high humidity both before and after inoculation shortened the incubation period and greatly increased the degree of infection. Delaying the high-humidity treatment of inoculated seedlings did not decrease infection. Although infection occurred over a wide range of temperature, a regimen of 35 C day and 27 C night was inhibitory. Maximum infection occurred under a 30 C day and a 21 C night. An efficient inoculation procedure is proposed for brown-spot studies.

Additional keywords: Lecanosticta acicola, environmental effects, artificial inoculation.