Turfgrass, White Grub Control, 1983

Spring and summer applications of insecticides to golf course fairways were evaluated for efficacy in controlling white grubs. Treatments were applied in separate areas on 4 May and 17 Aug. Plots were 10 by 10 feet replicated four times in a completely random design. For each plot, liquid formulations of insecticides were applied by sprinkler can in 1 gal of water and irrigated after applicaition with 2 gal of water. Granules were applied with a hand shaker made from a pint jar with perforated lid; some treatments were irrigated with 2 gal of water while others were not irrigated (see table). Thatch in the test areas ranged from 0.25 to 0.5 in. thick. Four locations in each plot were sampled with a cup-cutter (4.24 in. in diam) to a depth of 3 in. The predominate species of white grub in both trials was the Asiatic garden beetle comprising 84 to 94% of the population on all sample dates. Samples were collected at 4 and 6 or 7 weeks posttreatment and mean values for each sample date were compared by ANOVA. Total accumulative precipitation during the trials was 4.05 and 6.62 in. at 4 and 7 weeks, respectively, for the spring application; and 3.50 and 4.05 at 4 and 6 weeks, respectively for the summer application. Spring application: Although the number of grubs in pretreat samples averaged 20.9/ft2, the population decreased to a less than optimum level of 7.6/ft2 (in control plots) on the 4 and 7 week posttreatment sample dates. There were no significant differences between treatments at 4 weeks posttreatment, but at 7 weeks all treatments except BAS 263 21 and Landrin were significantly different than the untreated. Summer application: At 4 weeks posttreatment, there was a significant reduction in numbers of grubs in all treatments except Landrin. At 6 weeks posttreatment, all treatments except Landrin and BAS 263 21 were significantly different from untreated controls. Oftanol and Triumph, with or without irrigation at application, were the superior compounds in these tests.