Control of Southern Masked Chafer and Japanese Beetle Grubs, 1990

Abstract

Abstract This study was conducted in a Kentucky bluegass plot at the University of Kentucky Spindletop Research Farm, 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. There was an endemic grub population of about 8 JB and <1 SMC grubs per ft2. On 21 Aug 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 about 18 inches apart, arranged in a randomized complete block with 5 replications and 12 treatments. Third instar SMC grubs were dug from an untreated rough on a local golf course on 30 Aug. Grubs were immediately taken to the experimental site and 10 active grubs were placed into each cylinder. Any grub that had not burrowed into the soil within 10 min was replaced. Cylinders were treated on 31 Aug, 24 h after grubs were introduced. Air temperature at the time of treatment was 79°F, with 72% relative humidity, clear skies, and 3 MPH wind. Liquid formulations were diluted with water and applied as a coarse spray to the turf using a hand-held, trigger-type sprayer. A total of 10 ml of diluted formulation was applied per cylinder (329 gal/acre). Granular formulations were weighed on a microbalance and sprinkled evenly into individual cylinders. The whole site was irrigated with about 1 inch of water immediately after treatments were applied. Plots treated with entomogenous nematodes (BioVector [= Steinernema carpocapsae], Biosys Corp., Palo Alto, CA) received 10 ml of dilute formulation at a rate equivalent to 2 billion nematodes/acre. The nematode treatment was applied midway through the irrigation period, so that those plots received both pre- and posttreatment watering. Following irrigation, the cylinders that received nematodes were shaded by covering them with window screen until the following morning, when the screens were removed. Shading and pretreatment irrigation were intended to create conditions favorable for high nematode survival. The plots were evaluated 19 DAT by removing each cylinder with a spade and examining the enclosed soil and turf for surviving grubs. Data were subjected to ANOVA, and treatment means were separated by LSD test.