This is Shannon, the summer student intern at the Food Security Institute.
In the past several weeks, I had the opportunity to contemplate the connections between our globalized food system, pesticide usage, and my own cooking habits. What prompted this contemplation? Unfortunately, I discovered that my kitchen had been infested by Plodia interpunctella, or as they are more commonly known, Indian meal moths.
***August 19th update: To clarify, I am discussing my home kitchen, at my house, in this post, not the kitchen at the Food Security Institute. Fear not, the kitchen at the Food Security Institute is moth-free!***
My discovery of the moths was rather abrupt and startling. One warm evening, I opened an overhead kitchen cupboard, and several small, brown moths flew out. Then I noticed some small white objects on the inside of the cupboard door. One of the small white objects then fell off the cupboard door, landed on the countertop, and began crawling around. On closer inspection, it turned out to be a moth larva. I immediately began inspecting my stored packages of rice, pasta, and dried beans, to see if the larva had any friends hiding therein. Several of the hefty plastic bags contained multiple moth larvae. When I found that my box of multi-grain cereal contained not only wriggling larvae, but several adult moths, I must confess I did what any rational, experienced foodie would do. After shrieking, running out of the kitchen, and succumbing to a two minute bout of serious heebie-jeebies (that is the scientific term, I’m sure), I turned to Google for more information. Allow me to share my findings with you.
Indian meal moths are a fairly common household pest in North America. They are found in kitchens, where they live off of stored foods such as grains, dried beans, flours, cereals, pasta, dried fruits, nuts, pet food, or birdseed. In severe infestations, they can also infest spices, teas, chocolate, crackers, or almost any food product not stored in an air-tight container. These moths originally come from Asia, and so they are more of a problem during the summer months when the weather is warm and humid, more closely approximating their native habitat.
These moths are an interesting example of the side effects of our globalized food system. As you are probably already aware, a lot of food eaten in North America is grown many thousands of kilometers away, sometimes on other continents. According to the World Watch Institute, the average food item eaten in North America travels an astounding distance of 2,500 and 4,000 kilometers from where it is grown to where it is eaten, which is as much as 25 percent more than the average as recently as 20 years ago. Indian meal moths are not a new occurrence in North America, as they were first described by an entomologist in New York in the 1850s. However, I wonder if their occurrence is more common now that much of our food comes from overseas?
So how does one identify these globe-trotting moths? You can identify an infestation by finding either adult moths or larvae (as I did), or by finding the cocoons that the larvae build so that they can pupate in to adult moths. The cocoons look like fine, sticky white webbing.
The adults are small, and often have two-toned colour markings (darker on the lower portion of their body, and lighter on the upper portion.)
How do Indian meal moths come to inhabit a particular kitchen? Usually, moths come in to a kitchen not as adults, but rather as eggs in dried food of some kind. For example, there may be eggs present in a bag of rice or lentils that you bring home from the grocery store. The eggs are less than half a millimeter in length, and so would be difficult to spot. Eventually, the eggs hatch, and voila, you have moths in your kitchen. The length of time it takes the eggs to hatch can be as short as several days in hot weather, or as long as 8 to 10 months.
So, now for the next two important questions: How does one get rid of Indian meal moths, and how do you prevent infestations in the first place?
Eliminating meal moths starts with eliminating all possible infested foods from your kitchen. Usually, this means throwing away most or all of your stored, dried foods, unless they were stored in moth-proof containers. The moth larvae are very small, and can get in to plastic bags (surprisingly, they are able to eat right through the plastic), cardboard boxes, some Tupperware containers, and non-sealed glass jars (for example, if you have re-used a spaghetti sauce jar and lid to store rice or flour.) Metal cans are fine, and sealed glass jars (e.g. a jar of unopened spaghetti sauce) are usually fine. Be sure to inspect any packages of food you are keeping for signs of webbing or larvae (e.g. look closely under the rim of jar lids.)
If for some reason you cannot throw away a food, then you can try freezing it to kill any larvae or eggs in the food. Food must be frozen for at least a week. Once you remove the frozen food from your freezer, you must store it in a moth-proof container. Throwing food away is probably a safer bet for preventing re-infestation.
After removing all the infested foods from your kitchen, then you must clean thoroughly.
It is imperative that you do not use pesticides in your kitchen, as getting pesticides near food, or areas where food is stored or prepared is a really bad idea, and potentially harmful to your health. Non-toxic ways of getting rid of these moths are available.
Start by removing everything from your drawers and cupboards. Then vacuum the insides of all your drawers and cupboards, using a brush attachment. Make sure to vacuum all surfaces, including the undersides of shelves, walls, doors, the ceilings and tops of cupboards. Pay special attention while cleaning to hard-to-reach areas, such as the crevices between shelves and cupboard walls. After vacuuming, wash all parts of your drawers and cupboards using hot water with a bit of bleach mixed in, and some dish soap too if you like. Also, spend some time cleaning other areas of the kitchen where spilled food could accumulate. Pull out your fridge and stove and clean behind them, and give your stove a thorough cleaning. After your cupboards have dried, you may want to wash your cans, jars, and dishes before putting them away. Be sure to check infrequently used dishes for webbing or larvae.
Throughout this strenuous cleaning process, be sure to kill any moths as soon as you see them. I used an electric bug zapper shaped like a tennis racket, and it was pretty effective. You can also purchase non-toxic moth traps from a hardware store.
Finally, you will want to prevent re-infestation of your newly cleaned kitchen. Continue killing moths on sight. When you purchase new food, keep it all stored in the refrigerator for at least one week past the time when you have seen your last moth. Also, you will want to get some moth-proof container for your food. One popular option is to use a glass jar with a rubber gasket and a latching lid.
You can also try Tupperware with very tight-fitting lids. You want to be sure that your storage containers are air-tight. To test this, fill the container with water, close the lid, and turn it upside down to see if any water leaks out. Store your dried foods in these types of containers, as it will help prevent re-infestation.
Finally, some people try to prevent re-infestation by freezing any new dried foods that they buy for at least one week before using them. This strategy should kill any moth eggs in your new foods. However, after thawing the frozen foods, their shelf life will be reduced to several weeks. You can try freezing larger bags of dried goods, and just thawing the amount you will need for two weeks or so, storing the thawed foods in glass jars in your cupboard. Alternately, you can store all new dried foods in moth-proof containers, so that if a new batch of moths comes in to your kitchen, they will be kept contained and not spread beyond their container.
Hopefully these tips will allow you to enjoy many happy, moth-free culinary adventures. If you would like more information on Plodia interpunctella, check out these resources: Washington State University Extension:
http://cru.cahe.wsu.edu/CEPublications/eb1396/eb1396.htmlNorthwest Coalition for Alternatives to Pesticides:
http://www.pesticide.org/pubs/alts/moths/indianmealmoths.html 
