Weed Control Efficacy of Sequential Herbicide Applications on Poa annua in Cool-Season Turfgrass

Abstract

Annual bluegrass (Poa annua) is one of the most persistent and problematic weed species in cool-season turfgrass systems, causing significant deterioration in turf quality and uniformity. The present study evaluated the efficacy of sequential herbicide applications for managing P. annua under field conditions in established turfgrass stands. Treatments included pre-emergence followed by post-emergence herbicide combinations applied at defined intervals, with assessments of weed density reduction, turf injury, and overall turf quality. Results demonstrated that sequential herbicide programs provided significantly higher control of P. annua compared to single application strategies. Pre-emergence herbicides effectively reduced initial germination, while subsequent post-emergence applications suppressed surviving seedlings and established plants. The integrated sequential approach resulted in sustained weed suppression throughout the evaluation period, minimizing reinfestation and seed bank contribution. Turfgrass injury levels remained within acceptable thresholds for most treatment combinations, with transient chlorosis observed in sensitive cultivars following post-emergence applications. Weed biomass reduction and percent control were significantly higher in sequential treatments, highlighting their superiority in long-term management. Environmental conditions, particularly soil moisture and moderate temperature regimes, influenced herbicide efficacy and weed emergence patterns. The study emphasizes that timing and sequencing of herbicide applications are critical factors in optimizing control outcomes. Overall, sequential herbicide programs offer an effective and practical strategy for managing P. annua in cool-season turfgrass systems, reducing reliance on repeated single applications and improving turf quality. These findings support the integration of chemical strategies with cultural practices such as mowing height adjustment and overseeding to achieve sustainable and long-term weed management in turfgrass ecosystems.