Minimized‐rate topramezone programs for goosegrass [Eleusine indica (L.) Gaertn.] control in Florida

Abstract

AbstractGoosegrass [Eleusine indica (L.) Gaertn.] is one of the most troublesome warm‐season grassy weeds in subtropical climates of the southern United States. Currently, postemergence options are highly limited, and goosegrass control (GC) becomes more difficult as plants mature. Among current options, topramezone can control mature goosegrass. Research conducted in Florida suggests that despite seemingly effective control, recovery may be occurring from surviving roots. Therefore, this study assessed strategies aimed to ensure the persistent removal of mature goosegrass populations of Florida ecotypes. Two greenhouse studies were conducted to evaluate the response of goosegrass at one to three tillers and 4–10 tillers to topramezone applied once at rates from 0.8 to 12.2 g a.i. ha−1 (study 1) and at total rate reduced to 6.1 g a.i. ha−1 applied once or equally divided into two, four, or eight biweekly applications (study 2). Single topramezone applications at 6.1 g a.i. ha−1 provided comparable GC and biomass reduction to single applications at 12.2 g a.i. ha−1. Reduced rate‐based split‐programs of two and four biweekly applications improved GC and its persistence over a single application as evidenced by a >250 increase in GC area under the progress curve and a >20 days increase in days over 80% GC. Among the proposed extended application programs based on the reduced effective rate of topramezone, the most promising consists of four biweekly applications at a 0.125× rate, equivalent to 1.53 g a.i. ha−1.