Log bioassay of residual effectiveness of insecticides against bark beetles

Abstract

Residual effectiveness of nine insecticides applied to bark was tested against western, mountain, and Jeffrey pine beetles. Ponderosa and Jeffrey pine trees were treated and logs cut from them 2 to 13 months later, and bioassayed with the three beetles. The insecticides were sprayed at the rate of 1 gal (3.8 l) per 40- or 80-ft² (3.6 or 7.2 m²) bark surface at varying concentrations. Effectiveness of treatment was based on reduction in length of egg galleries 2 to 3 weeks after initiating bioassay. All chemicals were quite effective for 2 to 13 months, except for malathion and Imidan which were relatively ineffective, depending largely on concentration and application rate. On the basis of equivalent amounts of lindane, the ranking ofeffectiveness ofinsecticides tested was as follows: (a) on western pine beetle: decamethrin > permethrin > lindane> Reldan > Dursban =~ Sumithion > Sevin; (b) on mountain pine beetle: decamethrin > permethrin > lindane> Dursban =~ Reldan > Sevin > Sumithion; (c) on Jeffrey pine beetle: decamethrin > permethrin > lindane > Sevin. The residual effectiveness of lindane was about doubled by adding 2 percent molasses, and high pH of water reduced effectiveness of Sevin. Other application parameters had little effect.