Horror Show: Are There Moths Lurking in Your Stash? Here’s How to Check.

Once upon a time, many years ago, a new knitter and enthusiastic spinner visited a fiber festival and returned home with a beautiful bag of wool. What she didn’t know was that buried deep inside the bag of fluffy, purple wool lay tiny eggs that would hatch into a monster and require hours and weeks and years of anxious vacuuming to eradicate.

I’ve been through it, friends, and I never want to experience a moth infestation again! Because my house is not only brimming with my personal yarn and fiber, but also loads of fiber for classes I teach around the country, I need to take moth monitoring and security seriously.

Are there monsters—I mean moths—under your bed? I’ll share some easy ways to monitor your yarn and knits, and then I’ll add some tips for preventing an infestation. Tackling a moth infestation once it has started is another spooky story for another day.

Monitoring for Moths

Left: Webbing clothes moth (Tineola bisselliella) in both larval and adult stages. Courtesy of Clemson University - USDA Cooperative Extension Slide Series, Bugwood.org. Right: casemaking clothes moth (Tinea pellionella). Courtesy of Mohammed El Damir, Bugwood.org

1. Watch for adult moths.

Most of the moths that are known to infest our beloved textiles are fairly small. Two common moths, the webbing clothes moth (left) and the casemaking moth (right) are about the size and shape of a grain of rice when they land. That makes it easy to identify them compared to other common moths of similar size that have wings outstretched when they land.*

These moths prefer darkness, so you are most likely to find them in closets or closed rooms, and they might be more active at night.

2. Look for larvae.

The larvae are what do the damage to our textiles. They eat protein fibers, and they are especially drawn to unwashed fibers. Raw fleeces shorn from the sheep are especially delicious, but even your favorite cowl that has been worn a lot or a sweater with a food stain can draw larvae. However, they will eat other fibers, too—cotton, synthetics, silk blend. Monsters, they are.

Webbing clothes moths have cream-colored larvae with russet-colored heads (depending on the age), but when you see casemaking larvae, you’ll see what looks like a little pill or fluff of fiber. This larvae builds a wooly case around themself, which will often reflect the color of what they have been eating, making them hard to see. Unfold sweaters and look carefully at skeins of yarn where the larvae could have tucked themselves away from view. Check for skeins of yarn with loose ends that have been broken mid-skein.

The casemaking clothes moth (Tinea pellionella) creates a fibery tube, making it a challenge to spot. Courtesy of Ryan Jones, Colonial Williamsburg Foundation, Bugwood.org

3. Check the bottom of bins and baskets.

One of the easiest ways to quickly see if moths are about is to look in the bottom of baskets, bins, and yarn cubbies. Eggs and frass (poo) will look similar to salt and pepper.

4. Order pheromone traps.

Sticky traps are designed to emit female moth pheromones to lure males. Traps for the two types of moths discussed here have different shapes and instructions, so be sure to read up on how to use them effectively. These are often easy to find online or from a local pest-control business.

Pheromone traps are not intended to solve the infestation; they are to monitor an area. If you see males in the trap, you’ll know to start looking for all life stages—adults, larvae, and eggs—in the area.

Pro Tip: Since some moths that could damage our stashes live in the environment, I only use pheromone traps in the winter. I don’t want to draw moths into the house!

A webbing-clothes moth trap hanging in Kate's studio closet. Photo by Kate Larson

Preventing an Infestation

Separate clean and unclean knits and fiber.

Keep socks and sweaters that you wear several times before washing separate from clean knits and stash.

Vacuum and toss.

Vacuuming is one of the most important ways that museums prevent unwanted visitors to collections. At home, we can vacuum behind baseboards, the back of closets, and even air filters. Wherever dust and lint build up, a hungry larvae could take hold. After vacuuming, remove the vacuum bag and place it in the trash (outside of the house).

When in doubt, freeze it!

The number one best way to protect your stash is to freeze anything made from animal fibers that comes into your home. I have a lot of yarn and fiber that passes over my doorstep, and every bit of it, from yarn samples I picked up at a festival to a thrift-store find, goes into a plastic bag and then the freezer for several days. (Use the coldest freezer you have.) Then, I take it out and let it sit IN THE PLASTIC BAG for two to three weeks. Freezing will kill adults and most larvae but not eggs. Letting the item sit for at least two weeks will give the eggs time to hatch.

Then, refreeze the bag. Leave it for several days, take it out and let it warm up. Then you can breathe easy and get knitting, knowing that you’ve kept the monsters away for another day.

— Kate

*Depending on where you live in the world, you might have other types of moths in your environment.