FOREST ENTOMOLOGY Effectiveness of Bifenthrin (Onyx) and Carbaryl (Sevin SL) for Protecting Individual, High-Value Conifers from Bark Beetle Attack (Coleoptera: Curculionidae: Scolytinae) in the Western United States

High-value trees, such as those located in residential, recreational, or administrative sites, are particularly susceptible to bark beetle (Coleoptera: Curculionidae: Scolytinae) attack as a result of increased amounts of stress associated with drought, soil compaction, mechanical injury, or vandalism. Tree losses in these unique environments generally have a substantial impact. The value of these individual trees, cost of removal, and loss of esthetics may justify protection until the main thrust of a bark beetle infestation subsides. This situation emphasizes the need for ensuring that effective insecticides are available for individual tree protection. In this study, we assess the efÞcacy of bifenthrin (Onyx) and carbaryl (Sevin SL) for protecting: ponderosa pine, Pinus ponderosaDougl. ex. Laws., from western pine beetle, Dendroctonus brevicomis LeConte, in California; mountain pine beetle, Dendroctonus ponderosae Hopkins in South Dakota; and Ips spp. in Arizona; lodgepole pine, Pinus contorta Dougl. ex Loud., from D. ponderosae in Montana; pinyon, Pinus edulis Engelm. in Colorado and Pinus monophylla Torr. & Frem. in Nevada from pinyon ips, Ips confusus (LeConte); andEngelmann spruce, Picea engelmanniiParry ex. Engelm. from spruce beetle,Dendroctonus rufipennis (Kirby) in Utah. Few trees were attacked by Ips spp. in Arizona and that study was discontinued. Sevin SL (2.0%) was effective for protecting P. ponderosa, P. contorta, and P.monophylla for two Þeld seasons. Estimates of efÞcacy could not be made during the second Þeld season in P. edulis and P. engelmannii due to insufÞcient mortality in untreated, baited control trees. Two Þeld seasons of efÞcacy was demonstrated in P. ponderosa/D. brevicomis and P. monophylla for 0.06% Onyx. We conclude that Onyx is an effective individual tree protection tool, but repeated annual applications may be required in some systems if multiyear control is desired.