Terry L. Amburgey

The efficacy of Guayule resin as a pesticide

Abstract Researchers from the United States are evaluating the nonrubber-producing extract (resin) of the guayule bush (Parthenium argentatum Gray) as a potential wood protectant against marine and terrestrial wood-destroying organisms in Panama. Wood treated with guayule resin was not attacked, or only lightly attacked, by limnorians (crustacean borers) after 45 months in Limon Bay. After 19 months in the Bay of Panama, treated wood was undamaged by teredinids but heavily damaged by pholads; both are molluscan borers. Treated wood was not attacked by termites of the genus Coptotermes during 33 months of exposure in the Panamanian rain forest. Termites of the genus Heterotermes had not attacked wood treated with guayule resin after 45 months in the Panamanian rain forest. A 20-week laboratory evaluation of guayule resin for efficacy against brown-rot (Gleophyllum trabeum, Antrodia carbonica, Formitopsis cajanderi, Lentinus ponderosa) and white-rot (Dichomitus squalens, Trametes versicolor, Ganodermas sp) fungi was performed. Statistical analysis revealed a significant inhibition of decay of the treated wood by these organisms. A 12-week laboratory evaluation of guayule resin for efficacy against soft-rot fungi was also conducted. None of the treated wood was damaged by soft-rot fungi.

Supplemental Treatments for Timber Bridge Components

A series of joint treatments on southern pine, red oak, and yellow-poplar were evaluated. These included treatments applied in holes that were subsequently capped, treatments applied to bolt holes and/or bolts, treatments applied to felt pads located between wooden members, and treatments applied directly to the surfaces of the joints. Water-soluble diffusible systems applied in holes adjacent to joints generally performed more poorly than expected because of the lack of rainfall during the exposure period. The notable exception was a copper-borate paste applied directly to the joint area. Application of a solvent-borne copper naphthenate with or without a water repellent to felt pads was also very effective. Water repellent alone and fumigant treatments gave unsatisfactory performance over the long term. To simulate hazards encountered by piling, kiln-dried untreated southern pine pole stubs that received various supplemental treatments were placed in the field for 41 months. Upon groundline evaluation of these test specimens, it was noted that seven preservatives or combinations of preservatives looked very favorable. The following treatments yielded sound stubs with no evidence of decay or insect attack: (1) copper-borate paste applied to the surface at and below groundline; (2) copper-borate paste applied to the surface at and below groundline plus boron rods inserted into holes near groundline; (3) copper-borate paste applied to the surface at and below groundline plus fumigant inserted into holes near groundline; (4) pentachlorophenol grease applied to the surface at and below groundline; (5) fluoride paste applied to the surface at and below groundline; (6) fluoride paste applied to the surface at and below groundline plus boron rods inserted into holes near groundline; and (7) fluoride paste applied to the surface at and below groundline plus fumigant inserted into holes near groundline.

Guayule Resin as a Protectant for Wood Against Attack by Various Marine and Terrestrial Wood-Destroying Organisms

The U.S. Navy has a large amount of wood in marine and terrestrial service, and this wood must be treated to protect it against depredation by wood-destroying organisms. Still, the annual cost for repair or replacement of wood damaged by marine borers, alone, amounts to about 25 million dollars (Pendleton and O’Neill, 1987); terrestrial wood destroyers add to this cost. Obviously, currently used wood preservatives are not entirely satisfactory; additionally, these preservatives are facing an uncertain future for environmental reasons. Thus, the Navy needs more effective, and environmentally acceptable, wood protectants to replace those in use. Pursuant evaluating for efficacy the by-product resin which this need, the Naval Research Laboratory is a marine and/or terrestrial wood protectant, accumulates during the production of rubber from guayule (Parthenium argentatum Gray). Guayule grows in the arid southwestern United States and in northern Mexico and is the source of natural rubber nearly identical chemically and physically to that obtained from Hevea brasiliensis. This multicomponent resin contains a wide spectrum of organics (Banigan, et al., 1982; Schloman, et al., 1983) including polyphenols, cinnamyl derivatives, and a variety of terpenoids. Past experience (Bultman and Parrish, 1979; Bailey, et al., 1979; Chan and Jurd, 1973; Bultman, et al. 1982) indicates that these compounds would be the most likely to impart a protective character to the resin.