Temperature Influences Creeping Bentgrass (<i>Agrostis stolonifera</i>) and Annual Bluegrass (<i>Poa annua</i>) Response to Bispyribac-Sodium

Abstract

Bispyribac-sodium is a POST herbicide that selectively controls annual bluegrass in creeping bentgrass, but inconsistent results with seasonal applications are believed to occur from temperature influences on bispyribac-sodium efficacy. Growth chamber experiments at the New Jersey Experimental Greenhouse Research Complex, New Brunswick, NJ, investigated three temperature regimes on ‘L-93’ creeping bentgrass and annual bluegrass responses to bispyribac-sodium. Annual bluegrass and creeping bentgrass exhibited contrasting responses to bispyribac-sodium as temperature increased from 10 to 30 C. Regressions of 4 week after treatment (WAT) data revealed as temperature increased from 10 to 30 C, required bispyribac-sodium rates for 50% clipping reduction (CR 50 ) of annual bluegrass decreased from 85 to 31 g ai/ha and required rates for 50% leaf chlorosis decreased from greater than 296 to 98, indicating increased herbicidal efficacy at higher temperatures. In contrast, required bispyribac-sodium rates for creeping bentgrass CR 50 increased from 200 to greater than 296 as temperature increased from 10 to 30 C. Bispyribac-sodium discolored creeping bentgrass 0 to 20% at 20 and 30 C and discoloration increased 10 to 50% at 10 C. Thus, warmer temperatures (20 and 30 C) increase bispyribac-sodium efficacy for annual bluegrass control with minimal bentgrass discoloration; however, cooler temperatures (10 C) have minimal efficacy on annual bluegrass and increase bentgrass chlorosis.