IMAZAPYR FOR COMMON BERMUDAGRASS CONTROL IN SOD FIELDS

Common bermudagrass [Cynodon dactylon CL.) Pers.] is a serious weed in sod production fields of the southeastern USA. Although several herbi cides control this species in row crops, control in sod fields general ly has not been acceptable. Field studies were conducted to determine the efficacy of imazapyr [(+/-)-2-[4, (1-methylethyl)-5-oxo-1H-imidazo l-2-yl]-3-pyridine carboxylic acid] for eradicating common bermudagras s and for subsequent herbicide effects on growth of 'Tifway' bermudagr ass [Cynodon dactylon x C. transvaalensis (L.) Pers.], 'Emerald' zoysi agrass (Zoysia japonica Stued. x Z. tenuifolia Willd. ex Trin.), commo n centipedegrass [Eremochloa ophiuroides (Munro.) Hack.], and 'Raleigh ' St. Augustinegrass [Stenotaphrum secundatum (Walt.) Kuntzel] planted in treated areas the year following applications. Single and one or t wo repeat applications of imazapyr at 0.8, 1.1, and 1.7 kg a.e. ha(-1) per application were made 1 June, 15 July, or 1 September and were co mpared with glyphosate [N-(phosphonomethyl) glycine] applied at 2.2 kg a.i. ha(-1) on the same dates. All herbicide treatments provided > 90 % control of the common bermudagrass. A single July application of ima zapyr at 1.1 kg a.e. ha(-1) eradicated (100% control) common bermudagr ass. Single applications of imazapyr were less injurious to the introd uced turf species than multiple applications at the same total rate. L ess injury to desirable species occurred in 1989 than in 1988, a year of limited rainfall. Bermudagrass and centipedegrass were injured less when planting was delayed until mid-summer the year following treatme nt, while spring plantings of St. Augustinegrass and zoysiagrass exhib ited little or no effects from imazapyr applied the preceding year. Re sults indicate that common bermudagrass can be eradicated by a single application of 1.1 kg a.e. ha(-1) of imazapyr, and desirable, warm-sea son turfgrasses can be successfully established the following growing season.