Response of Seven Turfgrass Species to Pyridate

Abstract

Pyridate, a photosystem II-inhibiting herbicide used since the 1980s in crops such as corn, cereals, and sorghum, shows promise for turfgrass weed control; however, its safety to turfgrass species remains untested. This study evaluated pyridate’s effects on visible injury, green cover, and dark green color index (DGCI) for eight weekly assessments across seven turfgrass species, including hybrid bermudagrass, creeping bentgrass, fine fescue, Kentucky bluegrass, perennial ryegrass, tall fescue, and zoysiagrass. Fourteen field experiments were conducted in 2024 using a randomized complete block design with four replications, testing pyridate at 350, 700, and 1400 g ae ha⁻¹ alone or combined with sulfentrazone (350 + 280 or 700 + 560 g ae ha⁻¹). Results showed significant injury at 7 days after treatment (DAT) across all species (P ≤ 0.0163), peaking at 35% for bermudagrass with the high pyridate-sulfentrazone mix under warm, moist conditions, but dissipating by 14 DAT. Green cover decreased most (52%) with the high mix in bermudagrass Trial 2, while plots treated with pyridate at ≤700 g ha⁻¹ matched nontreated cover. Dark green color index (DGCI) mirrored injury trends, with minimal impact from pyridate at 350 g ha⁻¹. Pyridate’s safety aligns with its metabolic detoxification in grasses, unlike broadleaves, while sulfentrazone exacerbated damage, consistent with prior turfgrass studies. At ≤700 g ha⁻¹, pyridate proved safe across species, suggesting potential for selective weed control in turfgrass systems. Higher rates or sulfentrazone mixes require caution due to transient injury. Further research should optimize application conditions and target turfgrass weeds to refine pyridate’s role in integrated management amid rising herbicide resistance in turfgrass systems.