White Grub Control, North Carolina, 1984

Abstract

Abstract Five soil-applied insecticides were evaluated for efficacy in controlling beetle white grubs in pastureland scheduled for Fraser fir* Christmas tree plantings. Grubs were found feeding on Fraser fir roots, causing tree mortality. The test pasture was thickly covered with a mixture of annual and perennial grasses accompanied by various broadleaf weeds. The pasture had been cut for hay 2 wk prior to insecticide applications. The mineral-organic Porter loamy soil (2-3% organic matter) located in Watauga Co. had a pH of 5.5, and average temperature of 15° C at a depth of 4 inches, and a moisture content of 22% by weight. Test plots measured 10 by 10 ft and contained average of 2.4 grubs per sq ft. Each treatment was replicated 5 times; the plots were organized in a completely random design. Pre-treatment grub counts were acquired on 2 Sep, with insecticides applied the same day. One sq ft of sod per test plot was turned back to expose grubs feeding in the rootzone. The sod was replaced without injuring the grubs. Liquid formulations were mixed with 1 gal of water per test plot and applied with a hand-pressurized portable sprayer. Granular formulations were applied with a 20-inch wide hand-pushed spreader. On 13 Oct, posttreatment grub counts were acquired by turning back a previously undisturbed sq ft of sod. Both surviving and dead grubs were counted. Percent population reduction was calculated from the number of surviving grubs and the number of pre-treatment live grubs.