Effects of Nonionic Surfactants on Ethylene and Chlorophyll Content of Poa pratensis Leaves Infected with Bipolaris sorokiniana. Charleen M. Ciaccio, Greenhouse Attendant, USDA, Southern Regional Research Center, New Orleans, LA 70179. Clinton F. Hodges, Professor of Horticulture and of Plant Pathology, Department of Horticulture, Iowa State University, Ames 50011. Plant Dis. 71:149-152. Accepted for publication 21 July 1986. Copyright 1987 The American Phytopathological Society. DOI: 10.1094/PD-71-0149.

Research was initiated to determine the effects of the nonionic surfactants Aqua-Gro, Hydro-Wet, and Surf-Side 37 on the endogenous ethylene and chlorophyll content of healthy and Bipolaris sorokiniana-infected leaves of Poa pratensis. Short and long exposure of uninoculated plants to the surfactants failed to cause any changes in endogenous ethylene. After inoculation, plants from all treatments showed an increase in endogenous ethylene that peaked at 48 or 72 hr and then declined by 96 hr; few differences occurred in endogenous ethylene of leaves between inoculated plants exposed to surfactants and inoculated water-treated plants. Surfactants induced increases and decreases in leaf chlorophyll content, most of which were not significant. Inoculation of leaves of plants exposed to the surfactants resulted in a progressive loss of chlorophyll over time, but in most instances, the loss did not differ from that in inoculated leaves of water-treated plants. Inoculated leaves of plants subjected to long exposure to Aqua-Gro and Hydro-Wet were exceptions; chlorophyll loss was decreased in the Aqua-Gro treatment at 96 hr and increased in the Hydro-Wet treatment at 72 hr. The responses are discussed relative to ethylene-chlorophyll-disease interactions.

Keyword(s): disease physiology, Helminthosporium, Kentucky bluegrass, leaf spot, wetting agents.