| Round-leaved mallow was the target of Canada's first registered bioherbicide, BioMalRTM, a conidial suspension of Colletotrichum gloeosporioides f. sp. malvae. The weed, once rare, occurred on about 50% of Nova Scotia farms surveyed in 1994 due to increasing importation of round-leaved mallow seed in western grain. Fifty-eight farms were visited in 2000 and 75% were found to have Colletotrichum gloeosporioides f. sp. malvae infected round-leaved mallow. The disease progressed rapidly throughout the summer in studies in three round-leaved mallow infested orchards. The pathogen reduced vegetative topgrowth by approximately 95% and seed production by 50% compared to plants grown in a disease-free nursery. Disease carry-over from year-to-year was low with only about 1% of seedlings infected by the pathogen in seed or infected plant debris from diseased sites. It appears that the pathogen can be introduced and persist in the environment and provide significant levels of control of this annual weed. |
