Evaluation of fungal pathogens as biological control agents for the paddy weed, Echinochloa species by drop inoculation

Control of an important paddy weed, annual Echinochloa spp. by inoculation with its pathogens was investigated under greenhouse conditions. Isolates of Exserohilum monoceras, E. rostratum, Bipolaris sorokiniana, Curvularia lunata, C. aeria, Colletotrichum graminicola, Pyricularia grisea, and Ustilago trichophora were obtained from diseased Echinochloa spp. collected in Japan. After selecting the most virulent isolate of each species, eight representative isolates were compared for their weed control activity against E. crus-galli var. crus-galli long awn biotype, using spray and drop inoculation. E. monoceras and C. lunata reduced the dry weight of plants by over 80 percent using both types of inoculation. Drop inoculation resulted in higher 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. ƒormosensis, E. oryzicola and E. colona which grow in Japanese paddy fields. C. lunata, however, exhibited low herbicidal activity against E. crus-galli var. ƒormosensis and E. oryzicola.