Impact of reduced rates of tiafenacil at vegetative growth stages on rice growth and yield

Tiafenacil is a new non-selective protoporphyrinogen IX oxidase (PPO)-inhibiting herbicide with both grass and broadleaf activity labeled for preplant application to corn, cotton, soybean, and wheat. Early season rice emergence and growth often coincide in the mid-southern U.S. with preplant herbicide application in cotton and soybean, thereby increasing the opportunity for off-target herbicide movement from adjacent fields. Field studies were conducted to identify any deleterious impacts of reduced rates of tiafenacil (12.5 to 0.4% of the lowest labeled application rate of 24.64 g ai ha-1) applied to 1- or 3-leaf (lf) rice. Visual injury 1 week after treatment (WAT) for the 1- and 3-lf growth stages ranged from 50 to 7% and 20 to 2%, respectively, while at 2 WAT these respective ranges were 13 to 2% and no injury observed. Tiafenacil at applied rates had no negative season-long impact as early season visual injury observed was not manifested in a reduction in rice height 2 WAT or rough rice yield. Application of tiafenacil directly adjacent to rice in early vegetative stages of growth should be avoided as visual injury will occur. In cases where off-target movement does occur, however, impacted rice should be expected to fully recover with no impact on growth and yield, assuming adequate growing conditions and agronomic/pest management are provided.