Residual Control of Southern Masked Chafer Grubs, 1989

This study was conducted on a Kentucky bluegrass plot in Fayette County, Ky. The established turf was on a Maury silt loam soil (fine-silty, mixed, mesic Typic Paleudalf) with pH 6.2. Thatch accumulation was < 0.25 inches. Replicated plots (6 × 6 ft) were treated with isazaphos (Triumph 4 E), trichlorfon (Dylox 80 WP), or isofenphos (Oftanol 2 F) on 23 Jun, 6 Jul, 20 Jul, 3 Aug, or 17 Aug, corresponding to 10, 8, 6, 4, or 2 wk before grubs were implanted into the turf. Rates (Al/acre) were a) Triumph: 2 lb; b) Dylox: 8 lb; and c) Oftanol: 2 lb. Treatments were applied as liquids using a CO2 powered sprayer that delivered 1.3 gal/1000 ft2. All plots were then irrigated with 0.75 inches water. There were 4 replicates/treatment/date, the plots for each date arranged in a randomized complete block design. On 29 Aug, turf/soil cores (6 by 6 inches) were removed from each plot and set inside 6-inch-diam by 7-inch-long sections of plastic pipe; the bottoms of the soil cores were even with the bottom of the pipe. A piece of fiberglass window screen was placed over the end of each pipe, and the pipes with cores were replaced in the plot. Plots were then irrigated. Third-instar SMC grubs were collected from an untreated golf course rough on 30 Aug. Ten SMC were placed into each cylinder; those that did not burrow into the soil within 10 min were replaced. A “remedial” treatment was applied to one set of plots on 31 Aug after grubs had been implanted to provide comparative data on effectiveness of insecticides applied when grubs were present. On 15 Sep, the cylinders were removed from the plot, the soil cores were broken apart, and the living and dead or obviously moribund SMC were counted.