Compatibility of the bioherbicide Myrotheicum verrucaria with selected pesticides

The plant pathogen, Myrothecium verrucaria (MV) is being evaluated as a bioherbicide of invasive weedy vines. Pan of this evaluation is the compatibility of MV with chemicals commonly used in agroecosystems. Commercial formulations of the pesticides acifluorfen (Ultra Blazer), glyphosate (Roundup Weathermax), propiconazole (Tilt) and pyraclostrobin (Headline) were tested for compatibility with MV. Colony diameter was recorded every 24 h for 10 d on potato dextrose agar (PDA) and on PDA amended with formulated pesticides. 50% reduction in colony diameter was achieved with approximately 0.2% giyphosate, 0.8% acifluorfen, 5.5 ppm propiconazole and 10 ppm pyroclostrobin. MV conidia were tolerant of incubation in aqueous suspensions of label recommended application concentrations acifluorfen, propiconazole and pyraclostrobin, but the tested formulation of giyphosate resulted in almost complete and immediate loss of viability. Some pesticides may act synergistically with bioherbicides by weakening plant defenses or reducing microbial competition, but there is a need to develop application methods that protect the viability and epidemiology of the bioherbicide.