Evaluation of sulfosulfuron and bispyribac-sodium for use in cool-season turfgrass

Sulfosulfuron and bispyribac-sodium are two herbicides being investigated for use in turfgrass. Annual bluegrass (Poa annua) and roughstalk bluegrass (Poa triviales) are key weed species in cool-season turfgrass that are difficult to selectively control postemergence. The objectives of this research were to evaluate sulfosulfuron and bispyribac to determine: (1) cool-season turfgrass tolerance; (2) effective annual bluegrass control strategies in Kentucky bluegrass (Poa pratensis ) or creeping bentgrass (Agrostis stolonifera); (3) appropriate turfgrass reseeding intervals following applications; and (4) foliar and root absorption of bispyribac into four cool-season turfgrass species.; Perennial ryegrass (Lolium perenne) and Kentucky bluegrass were more tolerant to single applications of sulfosulfuron than tall fescue (Festuca arundinacea), whereas Chewings fescue ( Festuca rubra ssp. commutata) was intermediately tolerant. Kentucky bluegrass was severely injured by bispyribac, whereas injury to perennial ryegrass, tall fescue and Chewings fescue was less severe and persistent.; Multiple spring and fall applications of sulfosulfuron reduced populations of annual bluegrass in a Kentucky bluegrass stand. However, turf quality was reduced in such aggressive programs. Summer-applied bispyribac reduced annual bluegrass populations in a creeping bentgrass fairway more effectively and with less injury than spring or fall applications.; Perennial ryegrass was safely reseeded two weeks after a sulfosulfuron application, whereas creeping bentgrass and Kentucky bluegrass required two to four weeks. All three species were safely reseeded two weeks after a bispyribac application.; Bispyribac applied only to foliage resulted in less growth reduction of annual bluegrass, creeping bentgrass, Kentucky bluegrass, and roughstalk bluegrass than applications to foliage plus soil, suggesting root uptake contributes to the activity of bispyribac. Foliar absorption of 14C-bispyribac into annual, Kentucky, and roughstalk bluegrass was greater than that of creeping bentgrass. Annual and roughstalk bluegrass accumulated more root-absorbed 14C-bispyribac per dry weight of shoots than creeping bentgrass and Kentucky bluegrass.; These studies demonstrated sulfosulfuron and bispyribac have great potential to impact weed control in cool-season turfgrass. Effective annual bluegrass control programs with bispyribac were developed for use in creeping bentgrass fairways. In addition, this research revealed factors that may influence bispyribac selectivity, such as increased absorption and translocation within annual and roughstalk bluegrass.