Environmental factors affecting brown-spot infection on longleaf pine

January 22, 2021

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.