| Abstract/Contents: | "Suppression of common bermudagrass was observed during a series of tests of crabgrass and goosegrass seedling weed control conducted during the mid 1980's. Pot studies showed that bermudas were suppressed more than zoysiagrass. These early results are summarized in a Proceeding of the SWSS 41: 123, 1988, paper. Field studies using rates of -0-, 125, 250, and 500 g ai/ha applied to common and Tifway bermuda and common and Meyer zoysiagrass were conducted during 1988 and 1989. In a series of timed tests, applications were made once on about 12 May, 8 June, and 10 July. Each application caused moderate discoloration and slight density reduction injury to bermudas, but recovery occurred within less than six weeks after treatment. Sequential applications where three repeat treatments were made on each of the three dates caused severe injury to bermudagrass and only slight injury to zoysiagrasses. But considerable bermudagrass recovery occurred late in the season. These results indicated the need for monthly applications throughout the growing season. Field studies using rates of -0-, 500, 1000, 2000, and 4000 g ai/ha with four or five monthly applications were conducted during 1989 and 1990. Mid October 1990 fresh clipping weights, respective to fenoxaprop rates, were 263a, 116b, 91b, 48b, & 41b for common bermuda; 281a, 193b, 163b, 95c, & 64c for Meyer zoysia; and 192a, 188a, 178a, 158ab, & 135b for Arid tall fescue. The fresh clipping weight data indicated greater growth inhibition than visual estimates of percent cover. Visual estimates of percent cover made on 7 May 1991 showed 81a, 22b, 4c, 0.2c and 0c for common bermuda; 100a, 96a, 80b, 38c, & 16d for Meyer zoysia; and 100% cover for all Arid tall fescue plots. An overall summary of results indicates an order of suppression as follows: common bermuda > Tifway bermuda >>> common zoysia > Meyer zoysia >> Arid tall fescue. The ACCLAIM 1 EC label (12.50% fenoxaprop) suggests beginning 200 g/ha applications at bermuda greenup and repeating at 28-35 day intervals for a total of 1208 g/ha/growing season (six applications) for suppression of bermudagrasses. Results of these tests indicate that bermudagrass in zoysiagrass lawns or sod fields would be nearly completely suppressed in one or two growing seasons by the label program. Seedling grass weeds would be controlled also. These data indicate that ample margins of safety against injury to zoysiagrasses and tall fescues are insured by the label program." |
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