Recommendations for control of cone and seed insect pests of black spruce, Picea mariana (Mill.) B.S.P., with insecticides

Abstract

Foliar sprays of dimethoate (1.25 g AI per tree) and permethrin (0.028 g AI per tree), applied to run-off one week prior to female flower bud flush, significantly reduced flower abortion, cone grazing, and shoot grazing caused by spruce budworm, Choristoneura fumiferana (Clem.), larvae as well as damage by the spruce cone maggot, Strobilomyia appalachensis (Michelsen). Treatment with Bacillus thuringiensis var. kurstaki (B.t.) (0.012 B.U.I. per tree) resulted in moderate protection from grazing damage to female flowers and cones as compared to treatment with dimethoate and permethrin. Systemic applications of acephate also reduced damage by spruce budworm larvae and the spruce cone maggot: fall and early spring applications were equal in efficacy, and the label rate (0.875 g acephate/3.2 cm dbh) provided similar protection to the half-label dose.