Biological Control of Kudzu ( Pueraria lobata ) with an Isolate of Myrothecium verrucaria

Abstract

An isolate of the fungus Myrothecium verrucaria ( MV ) was evaluated for biocontrol potential against kudzu ( Pueraria lobata ). In greenhouse tests, MV was highly virulent against kudzu in the absence of dew when conidia were formulated in 0.2% Silwet L-77 surfactant (SW). Inoculum concentrations S 2 2 10 7 conidia ml -1 were required to satisfactorily control plants in the third leaf stage and larger. In controlled environment experiments, kudzu mortality was greater at higher temperatures (25-40°C) than at lower temperatures (10-20°C), although pathogenesis and mortality occurred at all temperatures tested. In field tests, transplanted kudzu seedlings in the 2-3 leaf growth stage treated with MV at 2 2 10 7 conidia ml -1 in 0.2% SW, exhibited leaf and stem necrosis within 24 h following inoculation, with mortality occurring within 96 h. After 7 days, 100% of inoculated kudzu plants were killed in plots treated with the fungus/surfactant mixtures. Similar results were observed in a naturally occurring kudzu population, where 100% control occurred within 14 days after inoculation with 2 2 10 7 conidia ml -1 in 0.2% SW. In summary, MV effectively controlled kudzu in the absence of dew over a wide range of physical and environmental conditions and under field conditions. These results indicate that, when properly formulated, MV has potential as a valuable bioherbicide for controlling kudzu.