Residual Efficacy of Triumph Vs. Oftanol for Control of White Grubs, 1990

Abstract

Abstract This study was conducted in a Kentucky bluegrass plot in Fayette Co., 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 inch. On 26 Jun we sunk 60, 8 inch diam cylinders made from PVC sewer pipe into the turf to a depth of about 3 inches. Implantation of cylinders was facilitated by cutting circular slits (8 inch diam) in the turf with a serrated-edge, cylindrical steel bit attached to a gasoline-powered soil auger. Cylinders were arranged in four groups of 15, representing the four treatment timings, and the three treatments were arranged in a randomized complete block within each timing group. Cylinders were treated with either isazophos (Triumph 4 E) or isofenphos (Oftanol 2 F) at 2 lbs AI/A, or were left untreated. Treatments were prepared by mixing 1.52 ml of isazophos or 3.04 ml of isofenphos in 1000 ml of water, and applying 10 ml of the respective solution to each cylinder using a trigger-type hand sprayer. The spray nozzle was adjusted to a coarse setting, and the amount of pesticide delivered per cylinder was carefully controlled by placing the sprayer siphon into a 100 ml graduated cylinder containing the diluted insecticide. Groups of 15 cylinders were treated on either 5, 31 Jul, or 16 Aug, corresponding to 56, 30, or 14 d before grubs were implanted. Third instar SMC grubs were collected from untreated roughs of a local golf course on 30 Aug, and 10 active grubs were placed into each cylinder. Any grub that had not burrowed into the soil within 10 min was replaced. The final set of cylinders was treated on 31 Aug, 24 h after the grubs were implanted. The cylinders were harvested on 14 Sep. The soil was carefully examined in large plastic pans, and the number of surviving grubs was counted. Because the site had a low population of masked chafer grubs, counts of SMC grubs represent mainly those that were experimentally implanted. The turf was also naturally infested with JB grubs, and surviving grubs of this species were also counted.