What's New At The Farm? 1/7/09

Moths flying out of my pretzel bag can't be a good sign. This week's article will be on Indian Meal moths; their identification, life cycle and control.

Indian meal moths are the most common pest of stored grains, seeds and flour products. They may be brought into your home in birdseed, dog food, flours and grains destined for your pantry, or any product that includes seeds or nuts in its makeup. Craft projects that incorporate grain heads can be home for enough insects to begin an unwanted population in your home. Open boxes of crackers, cereals and not-often used baking supplies (rarely used flours) make ideal homes and highways to bring the moths in. Nuts and seeds brought in by squirrels and mice can also harbor them.

One of the first indications you may have an infestation on your hands is their webbing. Webbing is often found inside bags of birdseed, especially if the seed is leftover from the previous year or stored where it's warm. Adults flying around are a give-a-way as well.

Identification of the Indian meal moth is relatively easy as the moth is about 3/8ths of an inch long with a wingspan of about 5/8ths of an inch. The overall color is dirty gray with some rusty brown on the tip portion of the wings. The adults do not feed, but rather are an indicator of a problem brewing.

The larvae is a cream colored caterpillar with a brown head about 2/3 of an inch long. It is capable of chewing through thin plastic and cardboard so keep this in mind when storing dry products. It can often be seen crawling ever so slowly where the walls meet the ceiling. These caterpillars are looking for a place to pupate. When pupating they surround themselves with a loose cocoon, and after pupating emerge as winged adults looking to mate and lay their eggs to repeat the cycle again. Three to four generations per year are common.

Now that you've got them, how do you control them? Notice I said "control" and not eradicate them. They're nearly impossible to eradicate without constant vigilance. The moths are easy to spot and easier still to kill as they are relatively a slow flying insect. A flyswatter will easily kill them; you can usually catch them while in flight although it's not as dramatic as catching a housefly in mid-flight. The larvae can be vacuumed up along with their webs when spotted. A thorough cleaning and checking of pantry supplies will go a long way in cutting their numbers down. Be aggressive in cleaning out the pantry. If a package is open or loosely sealed it probably has some eggs or larvae inside. For most products a trip to the compost pile or henhouse is in order.

A few things that "we can't live without" may be repackaged in a strong plastic or metal container and placed in a freezer for at least two weeks. Freezing will kill the adults and the eggs. Be fore-warned though that as soon as the product comes out of the freezer and put back on the pantry shelves it can become reinfested all over again. This treatment will only kill the insects, not remove them so if you see webbing or larvae you might toss these as well. The freeze treatment works best for products that have no signs of moth infestation but may be in close proximity to foods that do.

And so what to do once the moths' population is down or pretty much eradicated? I store all small batches of flours and baking goods in glass mason jars with tight fitting lids. Nuts, large bags of flour and whole or coarsely ground grains (like rolled oats) get stored in the freezer, especially in the warmer months when we don't use them so often. If I buy birdseed in the summer, it gets the two week freezer treatment then gets stored outside in an unheated building. Bird seed bells also get stored outside and dried ornamental corn gets put out for the squirrels. When buying bird seed check the bags, especially around where it is stitched, for larvae and webbing; if you see any don't buy it or at least store it outside.

Pheromone traps are available for the moths, but since they only attract the male moths their effectiveness for control is somewhat questionable. Traps should be used to monitor populations and if a population is discovered then the above mentioned controls can then be implemented.

Until next week, Brian