Insecticide Dips for Control of Japanese Beetle and Other Soil-Infesting White Grubs in B&B Nursery Stock

Abstract

Abstract Studies conducted in 1996, 1998 and 1999 show that immersion of root balls in Dursban® (chlorpyrifos) significantly reduces the number of white grubs, particularly Japanese beetle, Popillia japonica Newman, in B&B (ball and burlap) nursery stock. In 1996, the influence of root ball size, soil type, and dip time on the efficacy of Dursban® 50WP, Dursban® 4E, and Oftanol® 2F (isofenphos) for white grub control in dipped B&B nursery stock was evaluated. The grubs found within the root balls were primarily oriental beetle, Exomala orientalis (Waterhouse), European chafer, Rhizotrogus majalis (Razoumowsky), Asiatic garden beetle, Maladera castanea (Arrow), northern masked chafer, Cyclocephala borealis Arrow and Japanese beetle. With one exception, all the insecticide treatments caused similar grub mortality (96–100%) in 61.0 and 81.3 cm (24 and 32 in) root balls, respectively, and in sand or clay soil. There were no significant differences in grub survival due to dip time (1, 2, and 5 min). However, there were consistently fewer live grubs recovered from the root balls dipped 2 or 5 min compared with the number of live grubs recovered from root balls dipped for 1 min. In 1998, trees with 30.5, 45.7 and 61.0 cm (12, 18 and 24 in) root balls were dipped in either 0.453 or 0.906 kg ai/378.5 liter (1 or 2 lbs ai/100 gal) of Dursban® 4E for 2 mins. Both rates of Dursban® provided 100% control of Japanese beetle grubs in all three root ball sizes. Five trees from each treatment were planted one week after dipping and were evaluated for phytotoxicity up to 12 months after dipping. Most of the trees with 30.5 cm (12 in) root balls dipped in Dursban® died. Three of five trees with 45.7 (18 in) root balls dipped in the low rate of Dursban® and all five root balls dipped in the high rate had small leaves. One tree dipped in the low rate and 2 trees dipped in the high rate died 12 months after dipping. All of the trees with 61.0 cm (24 in) root balls dipped in the low rate of Dursban® survived and showed no signs of phytotoxicity. Trees with the same root ball size dipped in the high rate of Dursban® exhibited smaller leaves in 3 of the 5 trees. In 1999, trees with 61.0 cm (24 in) root balls were dipped in either 0.453, 0.226 or 0.113 kg ai/378.5 liter (1, 0.5 or 0.25 lbs ai/100 gal) of Dursban® 4E for 2 mins. All rates of Dursban® provided 100% control of Japanese beetle grubs.