Work on forest pests in New Zealand is concentrated mainly on those of the exotic trees Pinus radiata (Don) (q.v.), and Douglas fir, Pseudotsuga taxifolia (Brit). The main pests are the sawfly, Sirex noctilio (F.); the bark beetle, Hylastes ater (Payk.); and the defoliator, Selidosema suavis (Butl.), which is a native species. A campaign of biological control is being conducted against Sirex with Rhyssa persuaasoria (L.) and Ibalia leucospoides (Hochenw.). The Douglas fir seed chalcid, Megastigmus spermotrophus (Wachtl.), also gives trouble, and biological control is being attempted with Amblymerus apicalis (Thomson).

Buprestid beetles and Platypus spp. bore in living native trees, and in nursery areas there is trouble from the grass grub, Costelytra zealandica (Wh.); this latter is controlled with DDT.

The oak leaf miner, Lithocolletis messaniella (Zell.), which was a serious pest of exotic oak trees, has been very well controlled by the introduced parasites Apanteles circumscriptus (Nees) and Enaysma splendens (de L.).

Pests of milled timber are the common borer Anobium punctatum (De G.), the two-tooth longhorn, Ambeodontus tristis (F.), which is a native species; Lyctus spp., the introduced Australian subterranean termite; Coptotermes acinaciformis (Frogg.); C. lacteus (Frogg.), and C. frenchi (Hill), the native “dry wood” termite, Calotermes brouni (Frogg). Building timbers and the like are protected against these by impregnation with timber preservatives by diffusion or pressure before the timber is used for building. The injection of diesel oil gives good results against Anobium punctatum in existing buildings. This, however, will stain and may produce excessive oiliness on treated timber so that it is not suitable in all situations. Other materials that may be used are solutions of dieldrin and lindane in organic solvents, pentachlorphenol in kerosene, or, in the case of finely polished furniture, a mixture of nine parts of kerosene and one part of turpentine. This last is not long lasting and must be repeated every year about July or August. Termites may be killed by injection of arsenic dust into the workings.