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

Abstract

In greenhouse and controlled-environment tests, velvetleaf (Abutilon theophrastiMedic. ♯ ABUTH) and prickly sida (Sida spinosaL. ♯ SIDSP) control withFusarium lateritiumNees 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 × 105and 1.5 × 106macroconidia/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.