A Test of Foliar-applied Systemic Insecticides to Prevent Damage to White Spruce Cones by Insects

Abstract

Cone-bearing portions of white spruce trees were sprayed by means of hydraulic sprayers with 1.0 and 1.5 per cent solutions of dimethoate, methomyl, and acephate in a 12-year-old and a 25-year-old plantation. Cone damage was reduced by insecticides but no differences between the two application rates were detected. In the younger plantation, each insecticide provided highly significant reductions in damage by spruce coneworm, spiral spruce cone maggot, and spruce cone-axis midge, but neither reduced spruce budworm damage; there were no differences among insecticides. In the older plantation, each insecticide provided significant and equal reductions in cone maggot damage; seedmoth and cone-axis midge damage was reduced by dimethoate and methomyl, but not acephate, and no insecticide reduced coneworm damage. Some factors to consider in further testing of these or other insecticides for use against cone-damaging insects on seed trees are discussed.