Interaction Between a Velvetleaf Isolate ofColletotrichum coccodesand Thidiazuron for Velvetleaf (Abutilon theophrasti) Control in the Field

Spraying with tank mix combinations of the fungusColletotrichum coccodesand the plant growth regulator thidiazuron increased mortality, decreased biomass and height of velvetleaf, and increased soybean yield in field experiments. The velvetleaf isolate ofC. coccodeswas compatible with thidiazuron, and tank mix combinations consistently improved control over either component alone. In the moist 1986 season the fungus and the growth regulator interacted synergistically to increase velvetleaf mortality. In the drier 1987 season no significant interaction was detected between the two components.