Translocation and Efficacy of a Neem-Based Insecticide in Lodgepole Pine Using Ips pini (Coleoptera: Scolytidae) as an Indicator Species

Abstract

Recent research suggests that mountain pine beetles, Dendroctonus ponderosae Hopkins, may be controlled on pine using systemic applications of extracts from seeds of the neem tree, Azadirachta indica A. Jussieu. We investigated the extent of translocation of neem extracts in the bole of lodgepole pines, Pinus contora variety latifolia Engelmann. Because attacks by D. ponderosae do not always occur high on the bole of standing trees, the pine engraver, Ips pini Say, was used as an indicator species. A proprietary emulsifiable concentrate formulation of neem seed extract containing 20,000 ppm azadirachtin was applied into a basal axe frill around the root collar of lodgepole pines. After 1 wk the trees were felled and the logs were baited at 3, 9, and 15 m from the base with the pheromone ispdienol to induce attack by I. pini. Six weeks later, bolts were removed from the trees at the bait positions and held for a further 16 wk in rearing. At 3 and 9 m from the base, populations of I. pini (emerged and remaining under the bark) were significantly reduced by 87 and 77%, respectively, indicating that the active ingredients translocated at least 9 m up the bole and persisted for at least 6 wk. Numbers of emergence holes also were significantly reduced by 89, 88, and 63% at 3, 9, and 15 m, suggesting that the translocation extended beyond 9 m. Neem treatment had no impact on gallery construction and attack density, but significantly reduced the number of progeny per egg gallery. Unlike the currently used systemic arsenical, neem extracts would pose no toxicity to vertebrates and would have a short residual activity in the environment. There would be little chance of resistance developing because of neem's multiple modes of action and the fact that very few infested trees in a given year would ever be treated.