Potential Biological Control Agents for Goosegrass (<i>Eleusine indica</i>)

Abstract

Two leaf-spotting pathogens, [ Bipolaris setariae (Saw.)] and [ Piricularia grisea (Cke.) Sacc.], were isolated from severely infected goosegrass plants. Pathogenicity tests conducted at 28 C showed that both fungi were 100% effective in infecting goosegrass when given a 72-h dew period. Dew period temperature and duration requirements were tested by inoculating 2-week-old plants with conidial suspensions of each fungus and incubating them in dew chambers (100% relative humidity). Disease index increased as dew period duration increased for both fungi and at all temperatures tested. Infection occurred at all temperatures with an optimum of 24 to 28 C for B. setariae and 28 C for P. grisea . In host range tests, representative plants of the Fabaceae, Malvaceae, Poaceae, and Solanaceae were inoculated with suspensions of either 20 000 or 60 000 spores/ml of each fungus and placed in growth chambers at 28 C. Infection was limited to members of the Poaceae. Sorghum showed a hypersensitive response to B. setariae . Both cultivars of corn developed light symptoms in response to both fungi at 20 000 and 60 000 spores/ml.