Paraquat and glyphosate increase severity of strawberry anthracnose caused by Colletotrichum gloeosporioides.

Strawberry anthracnose caused by Colletotrichum gloeosporioides has recently become a major problem in Taiwan, in concurrence with herbicide use by growers. In evaluations of the effects of paraquat, glyphosate and glufosinate on C. gloeosporioides, anthracnose severity and soil microbial communities, paraquat and glyphosate promoted hyphal growth, conidial production and germination, and soil survival of C. gloeosporioides; glufosinate had inhibitory effects. Soil drench with glyphosate, but not paraquat or glufosinate, increased populations of fungi and yeast-like microorganisms. Anthracnose was more severe on leaves after either foliar sprays or drenches with paraquat or glyphosate than on controls without herbicide. Thus, a sudden outbreak of strawberry anthracnose is likely attributable to the stimulatory effects of herbicides on the causal pathogen. To minimize the inoculum potential of C. gloeosporioides and anthracnose severity, strawberry growers should eliminate any plant debris after herbicide treatment. [ABSTRACT FROM AUTHOR]