A hypothesis on a second non-biocidal property of wood extractives, in addition to toxicity, that affects termite behavior and mortality

IRG/WP 08-10638

T P Schultz, K Ragon, D D Nicholas

While it is has long been recognized that heartwood extractives affect termite behavior, the exact cause and relationship between total extractives, extractive types, and termite resistance remains unclear. Generally, researchers have proposed that the extractives are toxic and/or repel termites. We propose, based on the well known fact that many extractives have excellent antioxidant properties in addition to some termite toxicity, that: 1) the antioxidant properties of wood extractives interfere with the termite and symbiotic microbial digestion of lignocellulose; 2) thus, over time termites have learned to recognize and avoid wood with high levels of antioxidants; and 3) consequently, termites will also avoid wood treated with artificial and nontoxic antioxidants. Use of an artificial and nontoxic antioxidant will allow one to definitively test our hypothesis, while tests with natural extractives would be confounded by natural extractives often having both toxicity and antioxidant properties. We conducted some initial tests employing a man-made and benign antioxidant, BHT. In outdoor field trials, ground-contact stakes treated with only the antioxidant had less termite degradation than the control stakes at up to three years of exposure. An initial termite choice experiment using Reticulitermes flavipes Kollar (Eastern subterranean termite) was run with an untreated and 1- or 3%-BHT treated wafer in each jar, along with control jars that contained two untreated wafers. No termite feeding occurred on any of the BHT-treated wafers, indicting that the non-biocidal antioxidant was a strong feeding repellent. Furthermore, while only about 2% termite mortality occurred in the jars that contained two untreated wafers, in every jar that had an untreated wafer and a second BHT-treated wafer 100% mortality occurred. Recent no-choice laboratory tests with two subterranean termite species, R. flavipes and Coptotermes formosanus Shiraki (Formosan subterranean termite), and an exterior test with BHT-treated wood with Formosan termites, confirmed our initial results.

Keywords: antioxidant, butylated hydroxytoluene (BHT), heartwood, extractives, non-biocidal termite control, repellent, soil barrier treatment, termites, wood protection

Conference: 08-05-25/29

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