Impact of Reduced Rates of Tiafenacil on Early-Season Cotton (Gossypium hirsutum L.) Growth and Yield

Abstract

Tiafenacil is a new nonselective protoporphyrinogen IX oxidase-inhibiting herbicide with both grass and broadleaf activity labeled for preplant application to corn, cotton, soybean, and wheat. Early-season cotton emergence and growth often coincides in the Mid-South with preplant herbicide application in later planted cotton and soybean, thereby increasing opportunity for off-target herbicide movement from adjacent fields. Field studies were conducted in 2022 to identify any deleterious impacts of reduced rates of tiafenacil (12.5 – 0.4% of the lowest labeled application rate of 24.64 g ai ha-1) applied to one- to two-leaf cotton. Visual injury one week after treatment (WAT) with 1/8, 1/16, 1/32, and 1/64x rate of tiafenacil was 72, 54, 36, and 22%, respectively, whereas at four WAT these respective rates resulted in visual injury of 73, 67, 48, and 20%. Tiafenacil at these rates reduced cotton height 26 to 38% and 12 to 36% one and four WAT and seed cotton yield reduced 58, 38, 20, and 9%. Application of tiafenacil directly adjacent to cotton in early vegetative growth should be avoided as severe visual injury will occur. In cases where off-target movement occurs, impacted cotton should not be expected to recover fully and negative impact on growth and yield will be observed.