Treatment of 2-4 year old Sitka spruce in the field with the insecticides dimethoate, malathion, pirimicarb, Pynosect (pyrethrum + resmethrin) and Savona (insecticidal soap) applied as foliage sprays, and diazinon, chlorpyrifos and malathion applied as soil drenches, at standard rates, revealed no adverse effects on tree growth or needle densities. However, Savona caused needle browning and trees treated with chlorpyrifos showed a 25% increase in height growth (P < 0.01) and a 13% increase in side shoot extension growth (P < 0.05) after 2 years compared with control trees. Trials on potted plants with insecticides applied at the standard rate ( 1) or twice the standard rate ( 2) revealed no effects on height growth for any compound by the end of the growing season, but showed that all the insecticides tested had some effect on plant dry weight (DW) or needle density. Dimethoate and malathion at the 1 rate increased shoot growth, whereas malathion at 2 and Pynosect at 1 and 2 were noticeably phytotoxic. Root DWs were not increased or were reduced more than shoot DW, which led to significant reductions in root:shoot ratios. The low plant DWs in the Pynosect treatments were associated with a high rate of plant mortality (13-30%), whereas plant survival in the other treatments was generally good. Needle densities on the new leader were reduced by the 2 pirimicarb treatment and by both rates of Pynosect and chlorpyrifos. Needle retention on the previous year's leader was reduced by Pynosect and chlorpyrifos. Individual needles on the new leader were distinctly smaller on transplants sprayed with malathion or with Pynosect at the 2 rate, whereas needles remaining on the previous year's leader were heavier on trees in the 1 malathion treatment.