Imazapyr for Common Bermudagrass Control in Sod Fields

Abstract

Common bermudagrass [Cynodon dactylon (L.) Pers.) is a serious weed in sod production fields of the southeastern USA. Although several herbicides control this species in row crops, control in sod fields generally has not been acceptable. Field studies were conducted to determine the efficacy of imazapyr [(±)‐2‐[4,5‐dihydro‐4‐methyl‐4‐(1‐methylethyl)‐5‐oxo‐1H‐imidazol‐2‐yl]‐3‐pyridine carboxylic acid] for eradicating common bermudagrass and for subsequent herbicide effects on growth of ‘Tifway’ bermudagrass [Cynodon dactylon × C. transvaalensis (L.) Pers.], ‘Emerald’ zoysiagrass (Zoysia japonica Stued. × Z. tenuifolia Willd. ex Trin.), common 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 two 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 compared 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 imazapyr at 1.1 kg a.e. ha−1 eradicated (100% control) common bermudagrass. Single applications of imazapyr were less injurious to the introduced turf species than multiple applications at the same total rate. Less 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 treatment, while spring plantings of St. Augustinegrass and zoysiagrass exhibited little or no effects from imazapyr applied the preceding year. Results indicate that common bermudagrass can be eradicated by a single application of 1.1 kg a.e. ha−1 of imazapyr, and desirable, warm‐season turfgrasses can be successfully established the following growing season.