Use of Colletotrichum graminicola KA001 to Control Barnyard Grass

Isolates of Colletotrichum graminicola were obtained from barnyard grass showing anthracnose symptoms and the fungus was evaluated as a potential biocontrol agent. C. graminicola KA001 was highly pathogenic to two varieties of barnyard grass in a wide range of growth stages, with the most damage at the three- to four-leaf stages. Disease severity of barnyard grass increased with the increase of the inoculum density from 1 × 10⁴ to 1 × 10⁵ conidia/ml, but inoculum density above 1 × 10⁶ conidia/ml did not increase disease severity. A total of 13 rice cultivars tested showed no disease symptoms when inoculated with this fungus. Appressoria were formed on both barnyard grass and rice leaves, but infection hyphae were only found in the cells of barnyard grass. The fungus grew and sporulated in a wide range of temperature regimes, with optimal temperature at 27 to 30°C. These data suggest that C. graminicola KA001 has potential as a mycoherbicide to control barnyard grass with a safe selectivity in rice fields.