Factors Influencing Biocontrol of Velvetleaf (Abutilon theophrasti) and Prickly Sida (Sida spinosa) withFusarium lateritium

In greenhouse and controlled-environment tests, velvetleaf ( Abutilon theophrasti Medic. ♯ ABUTH) and prickly sida ( Sida spinosa L. ♯ SIDSP) control with Fusarium lateritium Nees ex Fr. was affected by inoculum concentration and plant growth stage at the time of inoculation, by postinoculative air temperature, and by dew period duration and temperature. A higher level of control of both weeds was obtained with inoculum concentrations of 7.5 × 10 5 and 1.5 × 10 6 macroconidia/ml when the weeds had fewer than seven true leaves. Postinoculative air temperatures above 25 C significantly reduced control of both weeds. Mortality of both species was higher at dew temperatures of 25 C than at temperatures of either 15 or 35 C. At least 12 h of dew at 25 C was required to achieve satisfactory control of prickly sida, while a dew period of 16 h was required to achieve a comparable level of control of velvetleaf.