Submitted to: Biocontrol Science and Technology
Publication Type: Peer reviewed journal
Publication Acceptance Date: 1/3/2000
Publication Date: 6/3/2000
Citation: Abbas, H.K., Boyette, C.D. 2000. Solid substrate formulations of the mycoherbicide colletotrichum truncatum for hemp sesbania (sesbania exaltata) control. Biocontrol Science and Technology 10:291-300. Interpretive Summary: COLTRU (Colletotrichum truncatum) is a fungus that has been shown to kill the weed hemp sesbania under certain conditions. This report involves a different and simpler method of growing this fungus on grain. This method allows good control of hemp sesbania when the preparation is fresh. COLTRU grown on rice has the advantage of longer storage time and remains active for 12 months at room temperature, 24 months in the refrigerator and 8 years when stored at -20 deg C. These findings will greatly extend the usefulness of COLTRU as a weed control agent.
Technical Abstract: Colletotrichum truncatum (COLTRU) was grown on kernels of eight different grains for 3 or 4 weeks at room temperature (22-24 deg C). Fresh preparations of conidia as well as fungus-infested corn and rice suspensions resulted in 100% mortality of hemp sesbania seedlings with a 12-16 hr dew period. Fresh preparations of mycelia and fungus-infested sorghum suspensions resulted in 90% and 65% mortality of hemp sesbania seedings with a 12-16 hr dew period, respectively. Lower mortality <15% occurred with the other ground fungus-infested grain suspensions. Fresh preparations of conidia, fungus-infested corn, rice and sorghum, and mycelia when applied pre-emergence resulted in 100%, 94%, 100%, 83%, and 71% mortality of hemp sesbania seedlings 14 days after application. Lower mortality (<23%) occurred with the other ground fungus-infested grain preparations. Freshly prepared COLTRU at 6.25, 12.5, 25, and 50 mg/cm**2 fungus formulated-rice applied pre-emergence or at the time of planting killed 97%, 100%, 100%, and 100% of hemp sesbania, respectively. After storage at 22-24 deg C for 6 to 24 mo., the rice formulation caused 67 to 93% mortality after 6 mo., 39 to 81% after 12 mo., and <2% after 24 mo., respectively. When COLTRU was refrigerated at 4-6 deg C., the rice formulation retained virulence of 76 to 99% after storage for 6 mo., 66 to 92% after storage for 12 mo., and 80 to 93% after storage 24 mo. Fungus-infested rice remained active for up to 6,7, and 8 years stored at -20 C against hemp sesbania and caused >80% mortality when tested at 6, 12.5, 25 and 50 mg/cm**2.