Non-insecticidal insect-proofing of wool

Abstract

Insect-proofing of wool is usually carried out by application of insecticides during dyeing. Inefficiencies in absorption of insecticide onto wool lead to aqueous effluent containing low levels of insecticide with a significant environmental toxicity to aquatic organisms. Replacing insecticides with non-insecticidal alternatives that target the wool digestion process of insects could greatly reduce the aquatic toxicity of wool processing effluent. Three classes of non-insecticidal compounds were investigated, including surfactants, naphthalene derivatives, and antimicrobials. Selected compounds were applied to wool fabrics for testing against wool-digesting Tineola bisselliella moth and Anthrenocerus australis beetle larvae. Anti-feeding effects were measured and used to form hypotheses on molecular shape, size and polarity and their contribution to insect-proofing. The antifungal propiconazole was chosen as the most likely compound to be targeting the wool-digestion process, as seen in Anthrenocerus australis larvae. To elucidate the mode of action of propiconazole on Anthrenocerus australis, repellency trials were carried out using control versus treated wool in reversible petri dish, and irreversible olfactometer choice experiments. No repellency effect was detected. Direct contact experiments were carried out by application of propiconazole solutions directly to Anthrenocerus australis larvae and by feeding larvae propiconazole-treated wool. No short or long-term toxic effects were detected, and subsequent feeding on untreated wool was not reduced. Gut enzyme activities were measured for Anthrenocerus australis fed control wool and compared to larvae fed propiconazole-treated wool. Trypsin, chymotrypsin, and aminopeptidase activities were significantly (p-value<0.05) reduced 2-2½ fold, although this could not be confidently attributed to enzyme inhibition. Gut morphology was observed in Anthrenocerus australis fed control or propiconazole-treated wool using microscopic examination of gut tissue sections prepared in a fixative, and stained to show relevant features of the gut wall and contents. No differences were seen between propiconazole-exposed and control larvae, indicating no cytotoxicity was conferred in the gut region by propiconazole. Lack of observed repellency or toxicity of propiconazole on Anthrenocerus australis larvae leads to the hypothesis that the anti-feeding effect may be caused by disruption of gut flora associated with wool digestion. Dyebath uptake experiments were carried out with propiconazole onto unbacked wool carpet, with susequent bioassays showing low absorption onto wool. Durability testing on the carpet using standard carpet shampoo and light exposure methods, followed by Anthrenocerus australis bioassay testing showed an acceptable durability of propiconazole on wool carpet.