Efficacy and Timing of Insecticide Sprays for Control of White Pine Weevil (Coleoptera: Curculionidae) in High-Value Pine Plantations

Abstract

Permethrin and methoxychlor were tested using two different exposure techniques in the laboratory for control of the white pine weevil, Pissodes strobi (Peck). Applied topically to adult weevils, permethrin was 121–183 times more toxic than methoxychlor. After being sprayed with permethrin, weevils were rapidly knocked down with an EC50 of 0.053 μg/cm2 after 1 d. The LC50 at 14 d was 0.095 μg/cm2. When weevils were exposed to white pine twigs that were dipped in the insecticides, permethrin was 43 times more toxic than methoxychlor. A rapid knockdown effect on adult weevils was also observed when weevils were exposed to white pine twigs that had been sprayed with permethrin. On potted trees, the residual toxicity of permethrin sprays applied at 0.16 and 0.4% concentrations began to decline noticeably after 4 wk; nevertheless, feeding punchues were still reduced by >98%. Field trials with selective leader treatments to jack pine showed that <5% of the leaders were destroyed by white pine weevil after treatment with permethrin at 70 or 140 g (AI)/ha, or with methoxychlor at 1.1kg (AI)/ha when applied soon after the adults emerged in the spring. Timing trials indicated that effective control (<5% leader damage) could still be achieved when permethrin and methoxychlor were sprayed 2–3 wk after the first adults had emerged.