Submitted to: Journal of Environmental Horticulture
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/22/2000
Publication Date: N/A
Citation: Interpretive Summary: Shipment of nursery stock infested with Japanese beetle grubs can introduce the beetle to new areas. Most uninfested states maintain quarantines or certification requirements to reduce the risk of introduction. The USDA, the National Plant Board and the regulated industry support the continuing harmonization of Japanese beetle quarantine and certification requirements to assure that the pest risks are acceptably managed and to facilitate the orderly marketing of nursery stock in a manner consistent with the National Plant Board Plant Quarantine, Nursery Inspection and Certification Guidelines. Dipping nursery stock in Dursban (chlorpyrifos) is the only acceptable option that allows growers to treat nursery stock within 3 days of shipping. Although dipping nursery stock can be difficult, messy and potentially hazardous because of the large volume of insecticide required, previous research has shown Dursban (chlorpyrifos) dips (the only product currently registered for this use) to be consistently effective at reducing white grub infestations in root balls. Current research has demonstrated that dipping B&B nursery stock with root balls 61.0 cm (24 in), for 2 min in Dursban at 0.113 kg ai/378.5 l (0.25 lb ai/100 gal), which is 1/8 of the recommended rate, effectively controlled white grubs. This study confirmed that dipping root balls of B&B nursery stock in Dursban can be an effective regulatory treatment for minimizing unnatural spread of Japanese beetle and potentially other white grub species. It is of immediate use to nursery growers and state and federal regulators who have an interest in the interstate and international movement of nursery stock.
Technical Abstract: Tests in 1996, 1998 and 1999 show that immersion of root balls in Dursban (chlorpyrifos) significantly reduces numbers of white grubs, mostly Japanese beetle, Popillia japonica, in B&B 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 grub control in B&B stock was evaluated. The grubs in the root balls were oriental beetle, Exomala orientalis, European chafer, Rhizotrogus majalis, Asiatic garden beetle, Maladera castanea, northern masked chafer, Cyclocephala borealis and Japanese beetle. Insecticide treatments were effective in 61.0 and 81.3 cm (24 and 32 in) root balls and in sand or clay soil. There were no significant differences in grub survival with dip time (1, 2, 5 min). However, there were consistently fewer live grubs in the root balls dipped 2 or 5 min compared with those 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 l (1 or 2 lbs ai/100 gal) of Dursban 4E for 2 min. Both rates of Dursban gave 100% control of Japanese beetle grubs in all three root ball sizes. Five trees from each treatment were planted one week after dipping balls dipped in Dursban died. All trees with 45.7 and 61.0 cm (18 and 24 in) root balls dipped in Dursban survived with some of the trees exhibiting smaller leaves and/or delayed development compared to the control 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 l (1, 0.5 or 0.25 lbs ai/100 gal) of Dursban 4E for 2 mins. All three rates gave 100% control of Japanese beetle grubs.