Influence of Environment and Inoculum Density on Penetration and Colonization of Sycamore Leaves by Apiognomonia veneta. Vernon Ammon, Associate Professor, Department of Plant Pathology and Weed Science Mississippi State University, Mississippi State 39762. Benson Graves, and Dot Griffin. Senior Entomologist, Division of Plant Industry; and Postdoctoral Assistant Professor, Mississippi State University, Mississippi State 39762. Plant Dis. 74:989-991. Accepted for publication 4 June 1990. Copyright 1990 The American Phytopathological Society. DOI: 10.1094/PD-74-0989.

Leaves of sycamore (Platanus occidentalis) seedlings were inoculated with conidial suspensions of Apiognomonia veneta to identify optimum temperature, postinoculation period of free moisture, and inoculum concentration required for penetration and colonization. Penetration was consistently high in artificially inoculated seedlings incubated at 100% relative humidity for 16 or more hours at 22–23 C. Inoculum containing 10⁵ conidia per millileter was optimum for seedling infection.