Weed Control and Bermudagrass Tolerance to Imazapic Plus 2,4-D

Abstract

Field studies were conducted during the 2000 and 2001 growing seasons to evaluate imazapic plus 2,4-D for weed control and bermudagrass tolerance. Imazapic at 140 g ai/ha plus 2,4-D at 280 g ai/ha or greater controlled dallisgrass at least 82% and provided at least 90% control of field sandbur, johnsongrass, and field mint. A mixed stand of Texas panicum and large crabgrass was controlled less than 75% and bahiagrass less than 25% with all rates of imazapic plus 2,4-D. Coastal bermudagrass injury was greater than 24% at three of four locations and Tifton 85 injury was greater than 50% at 3 wk after treatment with rates of imazapic plus 2,4-D as low as 70 plus 140 g/ha. Coastal bermudagrass yield was reduced at the first cutting with imazapic plus 2,4-D at 140 plus 210 g/ha and 240 plus 420 g/ha. Imazapic plus 2,4-D at 200 plus 350 g/ha reduced Tifton 85 forage production at the first two cuttings.Nomenclature: Imazapic, 2,4-D, dallisgrass, Paspalum dilatatum Poir. PASDI, field mint, Perilla frutescens (L.) Britt. PRJFR, field sandbur, Cenchrus incertus M. A. Curtis CCHIN, johnsongrass, Sorghum halepense (L.) Pers. SORHA, Texas panicum, Panicum texanum Buckl. PANTE, large crabgrass, Digitaria sanguinalis (L.) Scop. DIGSA, bahiagrass, Paspalum notatum Fluegge PASNO, bermudagrass, Cynodon dactylon (L.) Pers. CYNDA, ‘Coastal’, ‘Tifton 85’