Abstract/Contents: | Evaluated the effectiveness of turfgrass insecticides for control of masked chafer grubs in Kentucky bluegrass. Insecticides used were diazinon 14G and AG 500, Oftanol 5G, bendiocarb 76 W, Dursban XRM-4607 and 2E, Proxol(Dylox) 80W, Dursban XRM-4608, Dursban XRM-4414, and Deltic 30% EC. Fifty-six individual plots (2' x 2' = 4 ft2) were prepared by removing strips of sod with a mechanical sod harvester, so that a 1 foot boundary of bare soil surrounded each plot. To supplement the natural grub population and to provide a more uniform infestation level, grubs were collected on Aug. 18, 1981 by harvesting ca. 0.5 acre of sod adjacent to the test area. Twenty-two healthy 3rd instar grubs were immediately transferred to each test plot. When handled in this manner, masked chafer grubs immediately burrow beneath the sod. Granular treatments were mixed with 100 grams of fine sand and sprinkled evenly over the plots. Emulsifiable concentrates and wettable powders were mixed with 60 ml of water in a glass cylinder. The cylinder was then capped with a cork and alumimum sprinkler head of the type used when ironing clothes. After sprinkling materials evenly over the plots, the cylinder was rinsed with an additional 20 ml of water, which was also applied to the plot. All plots receiving liquid applications were immediately sprinkled with an additional 150 ml of water from a hand sprinkler can, to help wash the liquid materials into the sod. After the last treatment was applied, the entire test area was irrigated with 2- 2.5 cm of water. Surviving grubs were counted three weeks after treatment (Sept 11) by completely harvesting each plot to 6 cm depth with a mechanical sod cutter, and carefully examining sod and underlying soil for grubs. Data were subjected to analysis of variance, and the means separated by Duncan's multiple range test. Insecticides, application rates, and average number grubs/plot at 3 weeks after treatment are presented in a table. No photoxicity was evident with any treatment. Dead grubs were recovered from 5 treatments: Oftanol 2 lbs. (Total of 11), Oftanol 1 lb (4), Diazinon 14 G (5), Dursban XRM-4698 (3), Dursban XRM-4414 (1). Presence of dead, but not yet decomposed grubs may indicate that some materials, particularly Oftanol 5 G, may be slower working than others. |