Fungi Associated with Damping-off in Coniferous Seedlings in South African Nurseries

Abstract

Many fungi were isolated from diseased coniferous seedlings at various localities in South Africa. At least 9 species have not previously been isolated from conifers and some species are new records for South Africa. Based on occurrence rates and pathogenicity tests the most important fungi taking part in early damping-off were species of Fusarium, Pythium and Rhizoctonia. In late damping-off or root rot a wide variety of fungi appeared to be involved. Here Fusarium oxysporum and Cylindrocarpon destructans were the predominant pathogens followed by Rhizoctonia solani, Pythium ultimum, Diplodia pinea and Pythium debaryanum, in that order of frequency. Other virulent damping-off organisms viz. Phytophthora cinnamomi, Pythium irregulare, Macrophomina phaseolina, Fusarium moniliforme var. moniliforme. F. moniliforme var. subglutinans, Botrytis cinerea, Cylindrocladium scoparium and Fusarium. aquaeductuum var. medium occurred in seedlings of only a few nurseries.