Ground application of dimethoate (Cygon) for the control of cone and seed destroying insects of Douglas-fir and grand fir

Two concentrations of dimethoate were applied with a hydraulic ground sprayer to cone-bearing Douglas-fir and grand fir trees. Single application (mid-June) and a double application (mid-June and mid-July) were compared. Three of the four treatments applied to Douglas-fir resulted in a significantly higher number of sound seeds produced per cone compared to untreated cones. No seed protection was exhibited in the grand fir treatments.