The Identification of Foramsulfuron and Sulfentrazone Resistant Goosegrass (Eleusine indica) Populations

Abstract

Eleusine indica, commonly known as goosegrass, is a C4 weed species infesting turfgrass, cropping systems, and home lawns. Goosegrass is well known for developing herbicide resistance to different herbicide families and modes of action. Populations collected with suspected resistance were submitted to the Herbicide Resistance Diagnostic Lab at Auburn University to evaluate for resistance to six common herbicides used in turfgrass. Research was conducted in greenhouse conditions to assess susceptible (S) goosegrass responses compared to suspected resistant (R) biotypes. Based on the postemergence screen, 30 of the 50 populations were diagnosed as resistant to one or more herbicides. In contrast, 20 populations were diagnosed as susceptible to all treatments compared to the nontreated. Seventeen populations possessed cross-resistance to two or more herbicides. Since their discovery in 1995 and 1989, respectively, foramsulfuron and sulfentrazone have been widely utilized herbicides in turfgrass management. Despite their extensive use, limited research has been conducted on goosegrass biotypes resistant to these herbicides. Following initial postemergence screening, confirmed resistant biotypes underwent further analysis. Our research aimed to clarify the resistance level of these goosegrass biotypes by conducting dose-response assays with increasing rates of foramsulfuron (1.81 to 115.56 g ai/ha) and sulfentrazone (26.21 to 1677.78 g ai/ha). Visual injury ratings were recorded at 7, 14, 21, and 28 days after treatment (DAT), with aboveground biomass assessed at 28 DAT. Foramsulfuron-resistant populations (R-R1, R-R2, and R-R3) exhibited calculated I50 values of 0.12, 0.12, and 0.09, respectively, while the susceptible biotype displayed an I50 of 0.02. In comparison, sulfentrazone-resistant populations (D-R1 and D-R2) demonstrated I50 values of 0.11 and 0.21, respectively, whereas the susceptible biotype had an I50 of 0.03. Target-site gene sequencing of acetolactate synthase (ALS) and protoporphyrinogen IX oxidase (PPO1 and PPO2) indicated no mutation in the resistant biotypes compared to the susceptible, suggesting a potential non-target site mechanism.