Field exposure of Pinus heartwoods to subterranean termite damage (Isoptera: Rhinotermitidae, Mastotermitidae)

Abstract

Summary Four field trials were conducted to evaluate responses of the Australian subterranean termites Coptotermes acinaciformis (Froggatt) and Mastotermes darwiniensis Froggatt to untreated softwood timbers. The aim of the research was to determine whether the termite resistance of the heartwood of maritime pine (Pinus pinaster Aiton) and of the F1, hybrid of slash pine (P. elliottii Englem. var. elliottii L. & D.) × Caribbean pine (P. caribaea Morelet var. hondurensis Barrett & Golfari) was equivalent to that of slash pine heartwood. Containers with test specimens of maritime pine heartwood and sapwood, and slash pine heartwood and sapwood, and F1, hybrid heartwood and sapwood, together with feeder specimens of radiata pine (P. radiata D.Don) sapwood, were prepared. These containers were placed on concrete brick assemblies, in above-ground, weather-protected situations in areas of high termite hazard. The work with C. acinaciformis was conducted at Beerburrum, in south-eastern Queensland, Australia, and termite responses were determined by losses of mass over a period of 17 weeks. The work with M. darwiniensis was conducted at Townsville, northern Queensland, and termite responses were determined by losses of mass over a period of 47 weeks. The ranking in susceptibility of the timbers is as follows: maritime pine sapwood > slash pine sapwood > F1 hybrid sapwood > slash pine heartwood = maritime pine heartwood = F1 hybrid heartwood. The heartwood of maritime pine and of the F1 hybrid of slash × Caribbean pines is highly resistant to damage by the subterranean termites C. acinaciformis and M. darwiniensis, when used in Hazard Class 2(H2) (that is, internally above-ground) situations. Accordingly, with respect to C. acinaciformis and M. darwiniensis, we recommend that limitations on the use of heartwood unpenetrated by preservative in H2 situations be removed from Australian Standards and State regulations for maritime pine and the hybrids of slash × Caribbean pines.