Insect protection of wool
Wool carpet damaged by Anthrenocerus australis.
Why does wool need protection from insects?
Some insects have the ability to digest and derive nourishment from wool. Synthetic and cellulose-based fibres do not face this problem. Wool products such as carpets, apparel and insulation can sustain visible damage which can ruin the aesthetic quality of the item. To remain competitive with other fibres, wool must be treated with compounds able to prevent insect attack.
Problems with insect resist agents
Presently, the wool industry uses synthetic insecticides for insect-proofing (such as a micro-emulsion of the pesticide permethrin) that are applied during the dyeing or scouring processes. Although most insecticide (98-99%) is absorbed by the wool, some remains in the aqueous effluent and can cause environmental problems if discharged into rivers or lakes. Usually industrial effluent is treated in local sewerage plants, although strict effluent limits are still imposed on dyehouses in most parts of the world, including New Zealand. These regulations can cause a problem for wool yarn spinners, who are unable to adequately insect-proof yarn without exceeding insecticide effluent limits.
Wool insect-proofing agents based on the synthetic pyrethroid insecticide bifenthrin were first introduced in the 1990’s. Advantages of bifenthrin over permethrin include better durability to washing, greater effectiveness at low levels, no beetle-resistance problem and a significantly lower environmental impact in aquatic ecosystems. Marketed by Melbourne Aniline & Lye (Australia) and Shamrock Group Ltd (New Zealand).
Mystox MP, an agent based on the broad spectrum halogenated pyrrole insecticide chlorfenapyr, was introduced in 2007. No resistance is expected to develop in the wool-damaging species in the near future as chlorfenapyr is relatively new to the market. Chlorfenapyr has a similar toxicity to aquatic life, but better wash and light fastness than bifenthrin. Marketed by Murphy & Son Limited (UK) and Shamrock Group Ltd (New Zealand).
Surfactant-based Ecolan CEA can also be applied to wool during dyeing, and protects wool from insect attack. It is biodegradable, and possesses a lower aquatic toxicity than insecticides. Marketed by Chemcolour Industries NZ Ltd (New Zealand).