Application Timing of two Insecticides for White Grub Control, 1990

This study was conducted in Lincoln, Nebr., on a Kentucky bluegrass golf course rough. Topography of the plot area was level. The predominant grass species was Kentucky bluegrass (95%) with a thatch accumulation (finger compressed) of 0.25 to 0.5 inches. Field conditions at the study site were: soil type, silty clay loam; soil organic matter, 3-5%; soil pH, 6.7; water pH, 7.0; soil moisture was maintained near field capacity throughout the study. There was no prior history of Oftanol or Triumph use in the treatment area. Plots were 5 × 5 ft, and the experimental design was a randomized complete block with 4 replications. Liquid formulations of Oftanol and Triumph were applied 18 Jun, 3 Jul, 2 Aug and 17 Aug, corresponding to 30 and 15 d before, and 15 and 30 d after the anticipated date of 95% completion of the SMC beetle flight period (18 Jul, based on light trapping records from the last 4 years). Subsequent light trap collections indicated that 95% beetle flight actually occurred on 17 Jul at the study site. Insecticides were applied with a CO2 sprayer using a LF-4 nozzle at 24 psi and 5 gal/1000 ft2 spray volume. Immediately following applications the test area was irrigated with approximately 0.75 inches of water. A total of 12.9 inches of rain fell during the study period (18 Jun to 30 Aug). Product efficacy was evaluated 30 Aug (14 days following the last application) by removing from each plot six, 8-inch diam turfsoil cores (2.0 ft2 total area) to a depth of 3 inches and counting the number of surviving grubs.