9.02.2012

Clothes Moths

The shame of wool moths. Nobody likes to talk about it, but let's face it: many bikers, especially randonneurs, own their share of wool, and that wool is not always stored clean. These conditions favor wool moths. What I've learned might be useful to others, and if anyone has more knowledge to share I'd like to learn more.

We had a wool moth infestation. It probably traveled up with me from Portland, lay dormant for years, and resurfaced in 2004 or so. I thought we cleaned the problem up, but I have now learned the measures I took were probably entirely ineffective. The moths came back last summer. (Or, it may have been an infection from a wool item bought used. Now I quarantine wool that comes into our house, regardless of whether it was bought new or used.) I threw out some expensive suits and one very nice wool hiking sweater. I took measures. The problem abated, but has not entirely gone away.

When the problem recurred last winter, I found moth damage on the sweater and two wool suits. I threw out the now hopelessly damaged items and started researching.

There are two problem moth species: the webbing moths and the casemaking moths. The casemaking moths are rare here, and the casings they leave behind are obvious. You can get pheromone traps for the webbing moths. The "Pro-Pest" ones seem to work well and are available via Amazon and etc. The traps attract male moths, which then get stuck to the trap. They are supposed to be good for 3 months, but seem to still be pretty effective after 6 months, at least at room temperature.

When I discovered the moths, I ordered some traps, and looked into what wool moths liked and what killed them. Clothes moths like dark, warm places that smell like humans. They lay their eggs in wool that has human sweat, urine, or the like on it, as this is what the larvae eat. Apparently they don't need the wool to live so much as our blood, sweat, and tears, so to speak. So clean wool is usually safe. Besides wool, moths will sometimes infect silk, down, and in rare cases even cotton.

Dry cleaning kills the moths, so everything dirty that was dry-clean only went straight to the cleaners. (Washing and drying clothes does not reliably kill moth eggs.)

Cold kills moths, but slowly. Suddenly taking clothes from room temperature to a cold freezer and leaving them there for a week should do it, but I am not super confident in this method.

Heat kills moths. Half an hour at 120 degrees should do it, so I cranked the sauna up to 140 degrees and put the remaining clothes in for about an hour. This method is more difficult than it seems. I used a radiant thermometer to find out what temperature the clothes were really at. Just because the room is 140 degrees doesn't mean the clothes are.

Permethrin kills moths. We have plenty of permethrin around. It's an insecticide. We treat clothing we are going to wear in areas where malaria is endemic. Once it dries on the clothing, it's almost entirely non-toxic to people. Also, permethrin repels bed bugs. We've never had bed bugs, but we visit a variety of hotels, so I treated our luggage inside and out with permethrin to discourage bed bugs from hitching a ride on our luggage. And, permethrin kills clothes moths. So I put on a respirator and the big rubber gloves and sprayed down all of the seams and crevices of all the closets that had had wool in them.

The permethrin and sauna treatments were hot, sweaty jobs, but seemed to work. I put the moth traps in the closets, and, well, moved on.

But I did some more research. I found out two interesting things:
- Moth speed of development is highly temperature dependent. This means that they are more likely to emerge in the summer.
- Carbon dioxide kills all life stages of moths.

A CO2 concentration of as little as 15% should kill moths eventually, and higher concentrations should kill them in a few days. I decided that, to be sure, I'd shoot for a CO2 concentration of over 95% and hold it for a week.

My first test was with a more-or-less airtight plastic storage box that I put the skiing woolens in at the end of ski season. I put about half a pound of dry ice wrapped in a rag at the bottom, put a heavy book on the lid, and left the latches open. As the dry ice sublimated ("melted"), the CO2 gas would collect at the bottom, and displace air at the top. At the time, I didn't have a real way of measuring if it worked, but recently I found out it had. It doesn't take long doing this to realize that you can smell really high concentrations of CO2. It's the smell of getting a fizzy drink up your nose, without the wet part. So, when I opened the box of winter woolens recently, I could smell the CO2 that had been there since spring. I have to think that any moths or moth eggs were long dead.

I had decided to treat our woolens once or twice a year, just to be safe. My method was to buy Space Bag storage bags. These bags seal air tight, and they have a vacuum port. (Several of these bags are shown in the picture, above.) Put the woolens in the bag with a chunk of dry ice wrapped in a rag. Suck all the air out. Close the cover on the port until the bag starts to inflate. Open the port. As the pressure inside the bag rises, it will push air and CO2 out the port, until the final CO2 concentration will be quite high. Leave for a week. It works great. I know, because after I open the bags after a week, I can smell the CO2 in the bag quite easily.

But a funny thing happened, just as I was about to embark on the Space Bag project: I had been checking the moth traps every week. Never a moth. I decided to Space Bag treat the woolens at the end of an unusually warm and dry August.

Literally as I was collecting the woolens to bag them, I checked the traps one last time. They all had moths, in some cases, quite a few. So now I know the traps work.

Where did the moths come from? I don't know. I literally checked all the wool and silk in the house, including carpets. Nothing. No holes, no dead moths, no webbing, nothing. Did they come from outside the house? Maybe. They might also have come from some bulky wool sweaters where damage might not be obvious.

Actually, none of my theories for where the moths came from are all that persuasive. So I don't really know. I treated with CO2. Most of the woolens are in airtight storage now, and almost all of the rest will be soon. I ordered fresh traps. I plan on treating the woolens twice a year until we go two years with no moths in the traps.

To be continued....

18 comments:

Dr Codfish said...

Nice!

I don't know about the rest of the country, I'm a native but these little home wreckers have deviled me on and off in various places I have lived almost as long as I can recall.

I like that you are trying to 'wipe out' your infestation but I think it is at least possible that these little devils come and go.

Some great tips, but if you are looking for that 'essence of retro', try moth balls, reminds me of visits to grandma's house. Actually I like your dry ice trick.)

Yr Pal Dr Codfish

Erik Nilsson said...

Thanks, Dr. C, for your comment.

I agree that it's likely our clothes moths invaded from outside. Most authors claim this doesn't happen much, but I think that this is the least implausible explanation in our case. Clothes moth invasions from outdoors during warm weather may be more frequent than is commonly believed.


I don't use mothballs for a couple of reasons. Both of the common mothball ingredients are likely carcinogens. One can cause a potentially lethal breakdown in red blood cells in children. (Although some children are more genetically vulnerable than others.)

Some plastics plastics softened by mothballs. Some clothes buttons or other features could be affected, as could the the clear plastic bins I use to store close. (These are the only light-weight, airtight ones I can find hereabouts.)

Finally, mothballs smell nasty, so I have to plan ahead to air out items well in advance of needing them. Of course, clothes items are vulnerable while they are being aired out. I could do some testing to figure out what plastics are affected enough to worry about, but hopefully somebody else will undertake that project.

I am sure there are situations where mothballs are the best solution, but CO2 is non-toxic to people in moderate concentrations.

jaka said...

How have the moths been this year? I live in Seattle as well, and have had a hell of a year with moths getting into carpets, sweaters, and the cracks of carpet tiles, where they eat pet fur. We didn't have any moth problem until one xmas party coat check that seemed to infest several people. But now we seem to see them flying around all the time, including pantry moths. I'll be trying the dry ice this week as I don't want to use pesticides and moth balls due to our health, sanity, and the the pets.

Erik Nilsson said...

Jaka,

Sorry you're having a bad moth year!

I think we must have been close to moth-free, but our traps have also been catching moths this summer! I think that it has been so warm, so maybe the moths have been unusually mobile.

Maybe clothes moths can move around more outdoors than people realize. I think moths may be able to survive for at least a short time on food residue in our recycling bins, so I am rinsing those bins out regularly now. I do it about every other time the recycling gets picked up, which works out to once every four weeks.

Supposedly, the moth eggs don't survive outdoors well, not because it is too cold, but because the eggs need to be attached to a food source to survive. I am beginning to think that the moth eggs may be able to overwinter in recycle and compost bins. So, I am going to make sure I get all of the recycle and compost bins something like clean at least once this winter.

Also, while there are pantry moths, my reading suggests that clothes moths will lay eggs on food in the pantry if they can't find a better place. So the "pantry" moths you're seeing may actually be clothes moths.

Anonymous said...

Thanks for the idea of the CO2 treatment. I've been battling clothes moths for about two years with washing and drying and storing clothes in large plastic bags. I still occasionally find a moth in a trap or see one flying around. I do have a dog and wonder if the moths are dining on fur behind big heavy furniture I can't easily and regularly clean behind?

I do think you are right about moths coming in from outside and able to travel farther than realized. I live in a townhouse in Seattle and about two years ago I noticed one or two moths flying in my house. I assumed the were the usual small outside moth that must have come in from near a porch light. Shortly there after a neighbor and I were talking at our garages and he mentioned how weird it was that so many moths were in his garage. He lifted up a towel and no joking dozens of moths flew off of it. I'm certain that is the source of my problem.

I don't want to use moth balls around myself or my dog but I'm going to give your dry ice treatment a try.

And do let us know when you have won the battle over the pesky pests.

Anonymous said...

Dear Erik:

My suggestions:

-Dow Agro Vikane Gas Fumigant at 10X for 48 Hours, either in your tented structure, or a moving truck. At $600 - $2K for the largest residential moving truck - 26 feet - this is the most cost - effective starting point, believe it or not. A true gas, it penetrates deeply, but leaves no active residue.

-Continuous Steam Cleaners, like Reliable's Enviro Series. Clothes, furniture, walls - do everything

-Dyson Vacuum, or high - quality durable vacuum - every single day - everywhere!

-Enamel Sealed Caldron, such as from Le Creuset. Iron on the inside, enamel on the outside. Boil clothes for 30 minutes, then reduce to a simmer. Most clothes are surprisingly durable, and this method like steam enlarges the fibrous pores so they can release debris, and organic soil. Use tongs to fish out very not clothes.

-Commercial laundry detergent - most have an alkaline base, and Ph of 8.5 - 11

-Oven, at the lowest temp of 175 FH for...well, I did clothes for 22 hours, without melt, and wood drawers for 6 hours. Bed slats fit in when racks are removed, and they are angled in the oven.

-CB - 80 insecticide

-ScotchGuard clothing water proofer. This stupid stain repellant seemed to work well as an alternative to CB - 80

-Pre - Wash clothes, and use an OXO ny.on bristle brush to brush them. This will remove organic soils - blood, sweat, urine, food, etc. - and help prevent their re - deposit on clothing fibers in the wash

-I tried Orange Oil, which has a strong active ingredient similar to that of turpentine. No, it's not healthy! The clothes survived.

- Rubis stainless steel tweezers, and a fabric shaver. Get rid or the protein strands that infects leave behind.

- UV Light for detection. UV - C sanitizes, but most don't meet FDA standards

-Dishwasher, top rack for steam and heat sanitize cycle

-Most importantly, get rid of stuff. Clutter breeds pests beyond the insect world

Anonymous said...

Dear Erik:

My suggestions:

-Dow Agro Vikane Gas Fumigant at 10X for 48 Hours, either in your tented structure, or a moving truck. At $600 - $2K for the largest residential moving truck - 26 feet - this is the most cost - effective starting point, believe it or not. A true gas, it penetrates deeply, but leaves no active residue.

-Continuous Steam Cleaners, like Reliable's Enviro Series. Clothes, furniture, walls - do everything

-Dyson Vacuum, or high - quality durable vacuum - every single day - everywhere!

-Enamel Sealed Caldron, such as from Le Creuset. Iron on the inside, enamel on the outside. Boil clothes for 30 minutes, then reduce to a simmer. Most clothes are surprisingly durable, and this method like steam enlarges the fibrous pores so they can release debris, and organic soil. Use tongs to fish out very not clothes.

-Commercial laundry detergent - most have an alkaline base, and Ph of 8.5 - 11

-Oven, at the lowest temp of 175 FH for...well, I did clothes for 22 hours, without melt, and wood drawers for 6 hours. Bed slats fit in when racks are removed, and they are angled in the oven.

-CB - 80 insecticide

-ScotchGuard clothing water proofer. This stupid stain repellant seemed to work well as an alternative to CB - 80

-Pre - Wash clothes, and use an OXO ny.on bristle brush to brush them. This will remove organic soils - blood, sweat, urine, food, etc. - and help prevent their re - deposit on clothing fibers in the wash

-I tried Orange Oil, which has a strong active ingredient similar to that of turpentine. No, it's not healthy! The clothes survived.

- Rubis stainless steel tweezers, and a fabric shaver. Get rid or the protein strands that infects leave behind.

- UV Light for detection. UV - C sanitizes, but most don't meet FDA standards

-Dishwasher, top rack for steam and heat sanitize cycle

-Most importantly, get rid of stuff. Clutter breeds pests beyond the insect world

Anonymous said...

Will putting clothes in a dryer for a half hour kill all phases of case making moths?

Erik Nilsson said...

Anonymous asks "Will putting clothes in a dryer for a half hour kill all phases of case making moths?"

Surprisingly, no. Half an hour isn't long enough, and it's not easy to use a dryer to kill moths.

AFAICT, eggs for both moths common in wool will likely survive a trip through the dryer. Elevated temperature will eventually kill all phases, but it's hard to know exactly what temperature clothes are in a dryer, and how long they are at the hottest temperature: they start out room temperature, warm up, and cool down towards the end of the cycle.

Also, of course, wet wool at a high dryer temperature will felt, resulting is a much smaller garment. That's usually not a desirable outcome.

If you have a sweater rack for your dryer, then you can put a dry garment on the rack and use a timed dryer setting. In theory, an hour at a temperature around 130 ºF should do it. However, I have not been able to reliably kill wool moths with this length of time at this temperature, using a sauna and a radiant thermometer, so that I had a much better idea of the temperature that the clothes were actually at than I could easily get with a dryer.

Audrey said...

how much Permethrin did you use? about a half ounce to a gallon of water? or did you use ml/mg?

Erik Nilsson said...

Audrey, I used pre-mixed spray permethrin to spray cracks and crevices in our closets, and to spray our luggage to repel bugs we might meet while traveling. I think the spray was 0.5% permethrin by weight.

For treating clothing, I used a permethrin kit and followed the instructions on the kit.

ALB said...

I have read numerous articles! some say cedar will kill all stages of the moth cycle, which I know isn't true. since all of the information published isn't correct, I wanted to verify another method. I have read that ironing the infested clothes will kill all stages of the moth cycle. Do you know if this is true? or do you have any more information on the process? such as temp, ironing both inside and outside of clothes etc?

Erik Nilsson said...

ALB, I do not have direct experience ironing, but I don't think it's generally agreed that ironing is an easy way to make sure you get rid of moths.

Wool is usually ironed at a low temperature, and usually isn't ironed both inside-out and outside in. Also, the heat lasts for only a short time. It shouldn't make your problem worse, but I can't assure you it will work, and I think it often won't.

Anonymous said...

Eric;
Thanks for the post. This was a couple of years ago; do you feel this solved your problem? Thanks Rachel

Erik Nilsson said...

Rachel,

Yes, I think I've solved my problem. It has been a couple of years since I have lost anything to wool moths. I have occasionally found moths inside the house that appear similar to wool moths, but within the last year, it appears that they all flew in from outside.

It took at least a year, probably two, to really get ride of clothes moths, fumigating with dry ice every 6 months or so. I still fumigate everything once a year just in case, and I still quarantine or fumigate new wool purchases. If I'm not in the mood to fumigate a new purchase, I just store it in a ziplock bag when I'm not wearing it until I want to fumigate. Since it came out of a bag, it goes back into one: easy to remember.

I have the fumigation process down now, so it's not a big job, even for the whole family's woolens. I buy about 5 pounds of dry ice from the grocery store. The bags I have the suits and coats in will fill up on about 150 grams of dry ice, so I put that in, wrapped in a a rag or an old sock, zip up the bags, then suck the air out with a vacuum cleaner, seal the valve, and just forget about them.

I have everything else in watertight bins. Those, I put 2x their volume in dry Ice, put on the lids, leave the latches open, stack the boxes, and put a few heavy books on the top one. I used to put the dry ice in a rag, but now I just put it in a leftover clear plastic container and shove it down the side. When the dry ice is gone, I close the latches and leave the boxes alone.

The formula for how much dry ice you need is 1.8 g per L. or 0.11 pound per cu ft. So measure or estimate the volume of your container in either liters or cu ft, then multiply by either 1.8 or 0.11 depending on your units to get the weight of dry ice to put in that container. For a container like my suit bags where I can suck out almost all the air but I can't easily vent from the top, use dry ice close to the maximum volume of the container. For a container like my waterproof plastic boxes that will push the oxygen out of the top, put at least 2x if not 3x the volume of the box as dry ice, and make sure there is weight but well less than 1 PSI on the lid. A couple of heavy books should do it. Be sure the dry ice is low enough in the box that it will flow out below the seal and fill the bottom. Most boxes have at least some dead volume in the lid above the seal.

Using this method, I can run to the store for about $10 of dry ice, parcel out the dry ice in about half and hour, and then forget about the whole thing for two weeks, after which I have high confidence of 100% kill. Not really a big burden at all, compared to losing an expensive suit.

During a heat wave like now, I probably get a 100% kill in a couple of days, but I let it go at least two weeks. A 99% kill is not nearly as useful as a 100% kill.

Good luck! Let me know what you do and how it goes.

- Erik

Teresa said...

Thanks for that last explanation of quantities. I am planning to try this method with yarn and using plastic boxes. Just curious about how bad the smell is and how long it takes to dissipate? (It cannot be as bad as moth balls.)

Erik Nilsson said...

The smell doesn't bother me, really. It's the same smell as comes off of a carbonated, unsweetened drink. CO2 is a gas, so the smell dissipates quickly.

We are normally exposed to CO2 all the time, so a little extra is no big deal However, CO2 at high concentrations is potentially dangerous. Could you be exposed to a dangerous concentration by doing CO2 fumigation? You'd really have to work at it, and even then, probably not. CO2 Is directly toxic at around 5% concentration in air, AFAICT, although many people, particularly those with health problems, will notice some effects like drowsiness at lower concentrations.

Getting even a small closet to 5% concentration of CO2 would be very hard. Keeping the concentration that high long enough to harm someone would be even harder, as CO2 will mix with the air inside and outside the house quickly. A small closet is about 250 cuft. 5% of that is 12.5 cuft, which you get from about 1.3 lbs of dry ice. At the end of the fumigation, all you'll have left is the volume of the box you are opening, which will likely be smaller than 12.5 cuft if you're putting it in a small closet. The rest of the CO2 would have leaked away over several hours after you put the dry ice in. So opening the box is not going to be enough. To cause a problem, you have to use way more dry ice than necessary, in a space with outstandingly bad ventilation. A submarine would definitely do, I think. A bomb shelter would be good. An ordinary closet, even with the door closed, isn't going to be enough.

Any more, I only put the approximate weight of dry ice to fill vacuum bags once, and enough dry ice to fill boxes at most 3x. So I'm never putting so much CO2 in even a small closet for it to be dangerous. It could be done. Somebody could put a whole 10 lb block of dry ice in a smallish box in, oh, a phone booth or something, then curl up with a good book with the door closed while all of that dry ice cooked out. That might be enough to be dangerous. Maybe.

But I'm cautious, so I make sure. I leave the closet door open when I'm fumigating in there, or else I take the boxes into a larger room. Is that necessary? By the math, no, it's not worth the bother, unless your clothes closet is a converted iron lung, and even then I think it's a tossup.

I'm not qualified to make recommendations for health and safety practices, but I can tell you what I do, which is to not fumigate in a confined space, because a little extra caution isn't a bad thing.

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