On WI visits, a question which always gets asked is “what’s the best way to stop clothes moths?” As yarn is a prime target for moths and I need it in perfect condition to sell, this is what I’ve learnt over the years from pest control experts, other shopkeepers and the internet.
In the UK there are three main culprits who chomp away at your natural fibres: common (aka webbing) clothes moths, case-making clothes moths and carpet beetles. The adults themselves do not eat yarn but they lay eggs on it and when those eggs hatch, the larvae do the damage. The warmer months – May to September – are prime moth season but due to central heating and mild winters, they can now party all year in your cupboards. Their lifecycles are flexible, and can completed within a month or take well over a year.
If you see one or two moths every now and then you probably don’t need to worry. If you see six or seven moths in quick succession, you’ve probably got a problem. (Three to five moths – quandary!) Don’t be tied to thinking the problem is where you saw them – the adults may be at one end of the room having already laid eggs at the other.
Traditional preventatives like cedarwood and lavender don’t work. They *might* deter an adult moth who doesn’t like the smell but they won’t kill eggs or grubs. You can’t rely only on direct sunlight or just small amounts of handling to disturb critters either. If you are lucky enough to keep fleecy animals, they can even live in fleece whilst it is on the animal.
So what do you do? Mothballs are illegal for a reason. There are newer chemical control methods like Pest Control Formula C which are safer. However, don’t rely on pesticides as a pre-emptive measure, as moths can build up resistance then cheerfully ignore them.
Here in the shop I have a system called Exosect. Dotted about are tabs of waxy powder impregnated with female moth pheromones. If a male flies in, it gets all excited thinking there is a super-sexy female nearby and heads towards a tab. Its getting-jiggy-with-it hopes are dashed, but it isn’t killed, and gets coated with the powder. As it then flies about, it scatters a trail of female pheromones. The males get overwhelmed with these fake pheromones so if a real female flies in ready to mate, she gets ignored and doesn’t lay any eggs. This is now available for home use, but is still expensive.
Pheromone traps are the next best method to prevent a problem, renewed every couple of months throughout the year. There are two different pheromone traps for different types of clothes moth and another for beetles (some brands specify which they target, others do not) and they all only target males. Keep items made of natural fibres out of harm’s way in airtight storage, even better vacuum-pack them, or pop them in bags and freeze them.
If you’ve got a problem, you need to clean everything (including the furniture), vacuum all the dust (which may contain eggs) from the cracks of the room and use insecticide. I have read you can use diatomaceous earth alongside or instead of pesticide, but not put it to the test. If you’ve got grubs already hiding, spraying the (fabric-friendly) types of pesticides might work on clothes and upholstery but isn’t going to help much if they are safely shielded by a nice thick yarn ball. Affected items worth salvaging can either be put in the freezer for a whole two weeks* or put in a low oven (56°C) for at least an hour** to kill off eggs and grubs.
*Some sources say a few days but friendly experts say that’s not enough.
**Some sources say 30 minutes, others say two hours. The experts specify a non-scientific “hour or two”. Kindly souls in 1982 tested out the quicker version, a microwave-as-death-ray-machine.