PREVENTION OF INSECT-CAUSED SEED LOSS IN DOUGLAS-FIR WITH SYSTEMIC INSECTICIDES

Abstract

Cone-bearing Douglas-fir trees in three localities on Vancouver Island were sprayed with the systemic insecticides Bidrin (0.35 and 0.75%), dimethoate, Sumithion, Meta-Systox-R, and SD 9129 (1.0 and 2.0%) when cones had reached the pendent stage of development. With the exception of Sumithion, all materials gave varying degrees of control over important insect pests of cones in this area, i.e. the gall midge, Contarinia oregonensis Foote, the cone moth, Barbara colfaxiana (Kft.), the seed chalcid, Megastigmus spermotrophus Wachtl, and the scale midge, C. washingtonensis Johnson.