I was recently called out to deal with an issue of clothes moth larvae that had damaged an heirloom rug of great sentimental importance to a homeowner. The owner of the establishment had been away on vacation during the Spring only to return to find her favourite rug had been devoured by clothes moth larvae.
Clothes moths (Tineola bisselliella) is common throughout Ireland. Traditionally it is associated with many natural animal origin products especially woollen fabrics, fur, feather and leather products. Fibres are bitten off and loose ends discarded, thus destroying much more commodity than is consumed.
Adult female lays up to 160 eggs during a 2-3-week period amongst fibres of suitable material for the larvae. They emerge at temperatures above 10°C and begin to spin silk forming a mat or tent like structure. During the spring they hatch in 4-10 days to give an active, white translucent larva. This grows up to 10mm in length and the head becomes darker in colour.
Each larva constructs a smooth-lined tunnel by weaving the silk in amongst excreta (frass) and particles of substrate. The resulting camouflage serves as a home throughout the larva development period. The caterpillar emerges at night to feed and returns to the safety of its web tunnel by day.
The breeding temperature range is 10°C to 30°C and around 70% humidity is ideal for the species. Development is dependent on the quality of food
material. The move away from fibres and furs of animal origin to synthetic fabrics has seen a decline in the severity and frequency of occurrence in recent years. However other species of insects have filled the gap particularly the carpet beetle and fur beetle.
Much can be done in the home to prevent damage occurring. Keep woollen clothes scrupulously clean. Moth damage occurs where food stains, perspiration or urine stains have occurred. Cleaning carpets regularly with a vacuum cleaner particularly in areas covered by heavy furniture such as a sideboard or piano. A residual moth proofer spray should be used in these areas. Where carpets are being fitted it is wise to spray the underside of the carpet around the edge of the floor before a carpet is fitted.
Moth larvae cannot exist in bright light and good ventilation. A good old-fashioned spring-clean by regularly airing stored blankets, furnishings and other woollen products out of doors on fresh sunny days. Give them a good shaking and brushing or shaking before folding and putting away.
Upholstered furniture is sometimes a good reservoir of moth infestations as larvae prefer to feed in dark secluded areas. Removing the covering from the bottom of the chair, followed by a thorough spraying with a residual pyrethroid insecticide can be effective against larvae control. Look for carpet damage in corners and secluded hard to reach areas. Good hygiene is essential and the use of a vacuum cleaner to remove larvae. Where there are valuable fabrics at risk then specialist moth control is required in the use of pheromone traps and monitors to detect early presence of adults. Contact ecologica.ie for more information on (086) 812 0435.
Mervyn Walsh, Field Biologist