Termite resistance of wood treated with copper (II) compounds derived from tri- and dialkylamine-boric acid complexes

The objective of this investigation was to evaluate the toxicity to termites and the leaching stability of copper compounds derived from triand dioctylamineboric acid complexes for protecting wood against termite at tack . Water inso luble copper Nmethyldioctylamine or copper N-dioctylamine and copper borate were precipitated in wood by the reaction of N-methyldioctylamine or N-dioctylamine-boric acid complex with copper sulfate. Wood treated with these copper (II) compounds was resistant to subterranean termite attack in a modified nutritive supplement test. High or complete termite mortality occurred at 0.08 pcf (or 0.2%) for unleached, and 0.89 pcf (or 2%) for leached blocks. A notable advantage of the copper compounds over conventional wood preservatives was that termites readily acquired toxic doses by slight feeding on the treated wood; thus, unlike wood treated with conventional wood preservatives, these copper treatments might protect nearby untreated wood from termite attack. The toxicity to micro-organisms of cationic and anionic alkyl and aryl compounds has been recognized for many decades and has been the subject of many investigations (3, 7, 8, 9, 12) since 1940. Because they are environmentally more acceptable than conventional wood preservatives, these agents have been investigated recently for protecting wood against wooddestroying organisms. Cationic alkyl compounds such as dialkylammonium compounds containing halides, acetates, or other anions (10, 11) and anionic alkyl and aryl compounds such as aryl and alkyl carboxylates containing copper ion (14) have been shown to be effective against wood-destroying fungi in laboratory soilblock tests. The increase in fungitoxicity of copper modified alkylammonium compounds has also been reported (4). The objective of this investigation was to evaluate the toxicity to termites and the leaching stability of wood treated with copper compounds derived from triand dialkylamine-boric acid complexes. The conversion of triand dialkylamine-boric acid complexes to copper compounds may have the advantages of decreasing water volubility and increasing fungi toxicity. This paper reports on the resistance to termites of wood treated with the copper compounds derived from triand dialkylamine-boric acid complexes and discusses the advantages of this treatment. In unpublished r e s u l t s p r i o r t o t h i s i n v e s t i g a t i o n , N methyldioctylamine or N-dioctylamine-boric acid complex as well as other alkyland arylamine-boric acid complexes were evaluated for fungal toxicity. Nmethyldioctylamine or the N-dioctylamine-boric acid complex was the most effective. These complexes which were incorporated into malt agar by the fungal growth method (13, 15) inhibited the brown-rot decay fungus Gloeophyllum trabeum (Pers. ex Fr.) Murr. at a concentration of 0.01 percent (100 ppm). Further reaction of these complexes with copper sulfate to form the waterinsoluble copper N-methyldioctylamine or copper Ndioctylamine and copper borate in wood were evaluated for fungal toxicity using Gloeophyllum trabeum. These results showed that wood treated with copper compounds derived from the N-dioctylamine-boric acid complex at 0.6 percent solution concentration had weight losses of 2.63 percent and 4.62 percent for unleached and leached samples, respectively. The effectiveness of the copper compounds in preventing the fungal attack on wood led to the investigation of the effect of these compounds on termite toxicity. The authors are, respectively, Research Chemist, Research Entomologist, and Research Chemist, USDA Forest Serv., Forest Prof. Lab., One Gifford Pinchot Dr., Madison,WI 53705. The authors wish to thank Leslie Ferge for conducting the exposures to termites. This paper was received for publication in Januarv 1985. Forest Products Research Society 1986. Forest Prod. J. 36(5):18-20.