PythiumSpecies Causing Damping-Off of Seedling Bedding Plants in Ohio Greenhouses

Abstract

Among 22 isolates comprising 12 Pythium spp. [P. ultimum, P. irregulare, P. debaryanum, P. spinosum, P. aphanidermatum, P. vexans, P. sylvanicum, P. mamillatum, P. pulchrum, P. paroecandrum, P. heterothallicum and P. graminicola] causing damping-off of bedding plants, the P. ultimum isolates were most consistently virulent. In a survey of Ohio bedding plant greenhouses, P. ultimum was isolated most frequently. All P. ultimum isolates collected demonstrated consistent virulence. The test conditions closely approximated the seed germination and incubation conditions in most of the greenhouses, suggesting that P. ultimum is the primary damping-off Pythium sp. in Ohio bedding plant greenhouses.