Topramezone for bermudagrass control and mitigation of seashore paspalum and creeping bentgrass injury with additive products

Abstract

Methods for managing bermudagrass (Cynodon spp.) invasion of seashore paspalum (Paspalum vaginatum Sw.) are limited. In 2016 and 2017, a field study at Auburn University evaluated ‘Tifway’ bermudagrass (Cynodon dactylon (L.) Pers. x C. transvaalensis Burtt Davy) control and ‘Sea Spray’ seashore paspalum injury following sequential applications of topramezone alone and in combination with triclopyr. Combining topramezone with triclopyr improves bermudagrass control and reduces seashore paspalum injury compared to topramezone alone. Topramezone + triclopyr at 14.6 + 690.4 g a.i. ha-1 applied sequentially controlled bermudagrass > 90% at 14 days after second application, however control decreased over time. Unfortunately, sequential applications of topramezone + triclopyr at 14.6 + 690.4 g a.i. ha-1 caused over 50% seashore paspalum injury and reduce turfgrass quality. Creeping bentgrass (Agrostis stolonifera L.) response to topramezone is highly variable and is influenced by rates, tank mixtures, and environmental conditions. The specifics of such factors remain poorly understood. The objectives of this research were (1) to evaluate topramezone injury at different application timings; and (2) study the potential safening of topramezone via combination with paclobutrazol, Fe chelate or a turfgrass pigment. Results from these studies indicate early-season application of topramezone is safe to creeping bentgrass at all rates examined. Late-season topramezone application caused greatest creeping bentgrass injury. This is likely due to the high temperatures that stressed the turfgrass during this period. Application of topramezone in combination with paclobutrazol, Fe chelate, or turfgrass pigment reduced visual turfgrass injury compared to topramezone applied alone, with paclobutrazol and Fe chelate reducing creeping bentgrass injury the most. We conclude that early topramezone applications with combinations of paclobutrazol, Fe chelate, or turfgrass pigment could safely be used on creeping bentgrass putting greens.