Can you tell I hold a grudge here? Hmm. Well, let’s get down to it. There are a lot of confusing “facts” and misinformation about clothes moths out there. I’ve developed a system for dealing with them that works well for me, but I still wanted to know, from a scientific perspective, what actually kills them? What temperatures can they tolerate? What about water, can you drown moth eggs? Etc. Some of these questions remain unanswered, and I’d still like to team up with an entomologist some day and nail down some specifics. BUT (this is a big but) not long ago I stumbled on this post at Juniper Moon Farm. They are doing some great stuff over there, and this was no exception. The author, Lisa Stockebrand, lays out some specific advice which I heartily agree with: cleaning is the best response to finding moths in your wool, and you can kill all stages of them with heat or by freezing.
UPDATE: Big thanks to astute reader Gabe, who pointed out that even though this blog has vanished, you can still read the original post in the web archive here: https://web.archive.org/web/20150612112534/http://www.fiberfarm.com/2013/03/moths-a-public-service-announcement
After I read this, I told Bryan about it, and how, even though of course I’d like it if our house was 100% moth-free (it’s not—they were here when we moved in—and it won’t be until all the old carpet is gone, all the baseboards are removed and cleaned behind, etc.) and of course I’m bummed that they have done damage in the past, at this point I’d rather have a system that works for dealing with them. Sure, it’d be great to have a completely moth-free home, but as soon as one of my knitting buddies accidentally brings over an infested ball of yarn, it’s not moth-free any more, and so I would stick with my system even if I did think we were free and clear.
Less than a week after this discussion, I took a bunch of my felt samples to a small event, where they were displayed right next to an item which had clear moth damage, cocoons on it, etc. So I had a bunch of felt to treat when I got home, and that got me thinking that now is as good a time as any to let you all know what I know about wool moths so far.
They Do Exist
Unfortunately clothes moths are alive and well in the 21st century. I guess people who have never heard of them grew up in the age of acrylic (actually worse than moths in my opinion). Those folks definitely have not cleaned out the houses of older relatives who worked with wool!
Although the moths themselves are definitely up to no good, scouting around for your most precious garments to lay their eggs on, it’s the larvae that actually eat the wool. They also eat fur, and mixed fibers containing wool or other animal fibers, and can survive on dust bunnies alone, especially if said dust bunnies contain pet hair. Supposedly they also eat silk, although I have never seen one on a pure silk garment. There are two common kinds of wool moths (at least here in the US) and they both look pretty much alike: usually tiny (less than a centimeter long) shiny golden moths with tattered-looking edges to the wings, and red eyes. The eggs are incredibly tiny, and the larvae, when they first hatch, are practically transparent, and thinner around than a sewing thread.
How, pray tell, do I know that last part you may ask? Well, one time, years ago, we came back from a long trip and there were quite a few moths flying around the house (the woolens were packed away but I was still pretty mad). After crushing the first couple dozen I could catch, I decided to capture a few and leave them in jar to see what would happen, in the spirit of “know your enemy.” Probably the most interesting and disturbing thing I found out was just how practically invisible the larvae are when they first hatch. I could easily give an item a thorough inspection and not see one at all. Probably the second most interesting thing I found out was that yes, a couple of days in my freezer does seem to kill them.
They Can’t Eat It if You’re Using It
This is the most important thing I’m going to write in this post, so take note: moths are not a threat to woolens you’re using, only those you’re storing. I have lots of wool clothes, and I just love them. I wear them all winter long, without worrying a bit that little things with wings will attack them. That’s because if you’re wearing something, it’s out and about, it’s in the light (which clothes moths don’t like), it’s brushing up against other things, it’s being cleaned and then worn again … in other words, even if a moth did lay eggs on it, chances are very high the eggs would be destroyed or brushed off before they hatched.
Store it Well if You’re Not Using It
When the weather warms up, I wash my woolens, bit by bit usually, and store them for the summer, in a suitcase in the garage. Dirty clothes are more likely to attract moths, not to mention it’s not good for the fabric to let stains and oils just sit there. In a weird way I kind of love doing this, and especially love opening up the suitcase in the fall when it’s full of wonderful things for winter. I hand wash everything except a large rug and my not-me-made coat, which go to the cleaners.
I also use plastic tubs to store yarn and fabric scraps, and some plastic bags inside those as well. When I worked at a museum, I learned that airtight plastic bags are not really a good choice for long term storage of textiles, you want some airflow, otherwise the air in the bag will become different enough from the air outside that just taking the textile out can damage or destroy it. But while plastic bags aren’t the best choice for preserving your grandmother’s wedding dress, they should be fine for keeping your yarn stash organized, as long as you open them now and then. In my mind, the absolutely ideal container for wool storage is one that seals tight to moths but not to air, which is why I use a suitcase (with a tight closing zipper) for summer storage. Whatever you use, make sure it closes tight enough to keep a little moth from wandering in. Moths can eat through paper bags and cotton to get what they want, but they only will if what’s in there really grabs their attention.
Cold definitely slows moths down, and may kill them if the conditions are right. I’ve had good results storing wool for felting, and materials for making my cashmere hats, in big plastic tubs that stay on my back porch year round. About half the year, it’s pretty cold out there, and usually freezes at night. I keep my knitting yarn bin out there for part of the winter too. The rest of the time it stays in the garage. I’ve also had good results storing wool yarn and fabric scraps that I’m not going to use right away in the garage, either in plastic tubs or in a cardboard box with the seams taped shut. Again: treat/clean things, then store them.
Two Mistakes You Don’t Have to Make
As my friend Tom says, “You don’t have to make this mistake, I have already made it for you.”
1. Don’t bring home a new wool rug without having it cleaned, especially if it’s imported and/or has been stored for a while. Seriously, take it straight to the cleaners when you buy it, then bring it home. Same thing with any old yarn or sweaters someone donates to you. Treat them (see below), then wash them, then use them.
2. Don’t assume that something which has been hanging in your closet for a while is moth-free, and put it away. Treat it and/or clean it every time before you store it.
How to Kill Clothes Moths
If you find moths in your house, I can’t recommend a better strategy than what’s in Lisa’s article, which I linked to at the top.
It appears, from the incident with the jar of moths as well as other anecdotal evidence, that the ordinary freezer attached to my fridge is enough to kill moths, although that has not been scientifically proven for all stages of moth life. There was also an incident in which a moth attack got started in a storage bin (see 2. above) but then halted, and the larvae appeared dead when I found them. I have a theory that, while the temperature was not low enough to kill the eggs, at some point it did freeze hard enough to kill the larvae. This was in the garage. This is just a theory.
When I brought home my felt samples that were possibly exposed to moth eggs, I decided to try treating them with heat, since I could cycle through everything I needed to treat in a day, rather than over weeks if I used the freezer. Lisa recommends temps over 120° F for at least 30 minutes. Washing in water over that temp also works, but I decided I’d rather keep the wool dry so that I could store it right away. I’ve also steamed small amounts of yarn above boiling water, the way you would a vegetable, and that should work as well, as long as the heat penetrates to the middle of whatever you’re steaming.
I did put a pan of hot water on the lowest oven rack, so that the heat I was exposing the wool to wouldn’t be completely dry. The lowest temperature my oven will set at is 170° F, and I went for 200° just for good measure. I put an old towel directly on the middle oven rack, and put the wool items, not too many at a time so that the heat had a chance to penetrate, on top of that, and set the timer for 40 minutes before taking them out and putting in the next batch. At the end, the only thing that showed any signs of scorching was where the towel touched the sides of the oven, so I suggest folding your towel so that it doesn’t touch the oven walls. I keep a baking stone on the top rack of my oven, and I left it there to hold heat. If you wanted to, I think you could also do two racks of wool at a time, as long as you allow time for the oven to heat back up after you load everything in.
When one batch was done, I put it somewhere clean, and while the last batch was heating, I wiped out the plastic storage bin I keep the felt samples in with a damp cloth, and let it dry in the sun. The cleaning part always seems like no fun at first, but once I’m doing it, it occurs to me that it was high time anyway, and it feels good in a spring-cleaning kind of way. When I put the samples back in the bin I felt confident that they were good to go.
This is in Lisa’s article, but I’d like to emphasize it: please please do not use mothballs. This is another thing I learned from working at the museum: mothballs are truly horrible, they are toxic to all kinds of creatures, including me. I’m pretty sure I left a few brain cells behind while going through their collection of furs.
And Finally, Spiders
A thought about spiders: another time we returned from our summer journeys to find that moths had hatched in the house, but this time most of them were in a spider web in the studio. Ever since then, I have let spiders be in the house (except if they’re in the sink, the bathtub, or building a web somewhere very inconvenient) instead of trying to relocate them outside. It started me thinking that the spiders, being so much smaller than I am, and adapted to eat bugs, and hungry, might be much much better than I was at finding moth larvae under the edges of the carpet, etc.
I can’t say for sure what difference leaving the spiders has made, but I will say that over the past few years, all these strategies combined have meant that I only see a couple of moths a year (and, um, SQUASH them) and more importantly, I’ve managed to keep all the things I care about from getting munched on.
There’s a lot here (phew!), but I still promise to update/post more as I learn more!