In greenhouse and field experiments conducted over 3 yr, tank mixtures of spores of the fungi Colletotrichum truncatum and Colletotrichum gloeosporioides, formulated in unrefined corn oil and Silwet L-77 surfactant, were evaluated as a mycoherbicide mixture for simultaneous control of hemp sesbania and sicklepod, respectively. In greenhouse tests, 100% mortality and dry weight reduction of hemp sesbania occurred 6 d after treatment (DAT), whereas 15 d were required to achieve 100% mortality and dry weight reduction of sicklepod. In field experiments conducted in narrow-row (51-cm) soybean test plots, a single application of the fungal mixture formulated as described controlled hemp sesbania and sicklepod 94% and 88%, respectively, 28 DAT. Neither fungus, applied as aqueous conidial suspensions, provided control of their respective weed hosts. These results indicate that tank mixtures of these anthracnose-forming pathogens can effectively control hemp sesbania and sicklepod with a single application.

Alternaria cassiae and Colletotrichum truncatum are bioherbicidal pathogens of sicklepod, and hemp sesbania, respectively. The effects of simulated rainfall followed by 12 h simulated dew application, immediately or delayed by 1 to 4 h, on disease severity and weed control were studied for each pathogen on its weed host under greenhouse conditions. After each simulated rainfall event, treated plants were placed in a dew chamber for 12 h. Regardless of rainfall amount and/or timing, only slight differences occurred on A. cassiae disease severity and sicklepod control (85 to 100% for both parameters). However, when similar tests were imposed on C. truncatum, disease severity and hemp sesbania control were highly variable, ranging from 5 to 100%. Regardless of rainfall amount, disease development and control of hemp sesbania were greatly reduced (60%) when dew application was delayed by only 1 h following inoculation, regardless of rainfall treatment. Rainfall at 1.27 and 2.58 cm had little effect on disease development and control in hemp sesbania, but the effect of transfer time to dew application exhibited a greater role on these parameters. Thus the time between bioherbicide application and dew application was more important for C. truncatum than for A. cassiae. These results indicate that rainfall amounts and the timing of dew application caused differential effects on disease severity and weed control after application of these bioherbicides to their target weeds.