Creeping Bentgrass Putting Green Tolerance to Bispyribac-sodium.

Bispyribac-sodium is an efficacious herbicide for annual bluegrass (Poa annua L.) control in creeping bentgrass (Agrostis stolonifera L.) fairways but turf tolerance and growth inhibition from applications may be exacerbated on closer mowed putting greens.  To test this hypothesis, field and greenhouse experiments investigated creeping bentgrass putting green tolerance to bispyribac-sodium.  In greenhouse experiments, creeping bentgrass discoloration from bispyribac-sodium was exacerbated by reductions in mowing height from 24 to 3 mm but mowing height did not affect clippings or root weight.  In field experiments, discoloration of creeping bentgrass putting greens was greatest from applications of 37 g/ha every ten days compared to 74, 148, or 298 g/ha applied less frequently.  Chelated iron effectively masked discoloration of creeping bentgrass putting greens from bispyribac-sodium while trinexapac-ethyl inconsistently masked these effects.  Overall, creeping bentgrass putting greens appear more sensitive to bispyribac-sodium than higher mowed turf but chelated iron and trinexapac-ethyl could mask discoloration.