Evaluation of fungal pathogens as biological control agents for the paddy weed, Echinochloa species by drop inoculation.
Control of the annual paddy weed Echinochloa spp. by inoculation with its pathogens was investigated in the greenhouse. Isolates of Exserohilum monoceras, E. rostratum [Setosphaeria rostrata], Bipolaris sorokiniana [Cochliobolus sativus], Curvularia lunata [Cochliobolus lunatus], C. aeria, Colletotrichum graminicola, Pyricularia grisea [Magnaporthe grisea] and Ustilago trichophora were obtained from diseased Echinochloa spp. collected in Japan. After selecting the most virulent isolate of each species, 8 representative isolates were compared for their weed control activity against E. crus-galli var. crus-galli using spray and drop inoculation. Using both types of inoculation, E. monoceras and C. lunatus reduced the dry weight of plants by >80%. Drop inoculation resulted in better weed control than spray inoculation. E. monoceras exhibited high herbicidal activity against E. crus-galli var. crus-galli (long and short awn biotypes), E. crus-galli var. formosensis, E. oryzicola [E. oryzoides] and E. colonum [E. colonum] which grow in Japanese paddy fields. C. lunatus exhibited low herbicidal activity against E. crus-galli var. formosensis and E. oryzoides.