Fungi Associated with Damping-off of Slash Pine Seedlings in Georgia

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Abstract
A survey of fungi occurring in pine seeds, diseased pine seedlings, and pine bark mulch at southern pine nurseries identified 41 taxa in 23 genera. Pathogenicities of 35 representative isolates from 12 species or taxa of fungi were tested on slash pine [Pinus elliottii] seedlings. Isolates of Fusarium moniliforme var. moniliforme, F. oxysporum, F. fusarioides, F. solani, Alternaria alternata, Rhizoctonia solani AG-4, binucleate Rhizoctonia-like fungus CAG-3, Pythium aphanidermatum, Penicillium expansum, and Cladosporium cladosporioides caused preemergence damping-off. Isolates of R. solani, a binucleate Rhizoctonia-like fungus, and P. aphanidermatum also caused significant amounts of postemergence damping-off. F. moniliforme var. subglutinans, F. m. var. moniliforme, and F. m. var. intermedium initiated infections from seedborne inoculum to the cotyledons. F. m. var. subglutinans was the most virulent of these three varieties of F. moniliforme. In growth chambers at 20 and 30 C, F. m. var. moniliforme, and F. m. var. intermedium needed higher temperatures to cause infections. This is the first report of F. m. var. intermedium causing a plant disease.