Subsurface Placement of Insecticides for Control of Southern Masked Chafer Grubs, 1992

This study was conducted in Lincoln, NE on a Kentucky bluegrass golf course fairway. The turf (95% Kentucky bluegrass) was maintained at a mowing height of 1.6 cm and thatch accumulation (finger compressed) in the plot area was 1.3 to 2.5 cm. Field conditions at the time of application were: air temperature, 25.°C; soil temperature (10-cm depth), 26.°C; soil type, silty clay loam; soil organic matter, 3-5%; soil pH, 6.0 to 7.0; water pH, 7.0; soil moisture, 17%. Plots were 1.1 x 4.6 m and the experimental design was a RCB with 4 replications. Insecticides were applied 17 Aug; subsurface treatments were applied using a Cushman prototype subsurface applicator designed to place liquid or granular insecticides at the soilthatch interface (average depth, 1.9 cm). Conventional broadcast granular insecticide treatments were applied with a Grandy 24H12 drop spreader. Immediately following applications, plots were irrigated with 0.6 cm of water and the test area received an additional 0.6 cm of water from scheduled irrigation. During the post-treatment period, the trial area received approximately 3.8 cm of additional irrigated water. Treatments were evaluated 24 DAT on 10 Sep 1992 by removing from each plot six, 20.3 cm diam turfsoil cores (0.19 m2 total area) to a depth of 7.6 cm and counting the number of surviving grubs.