QUESTION:

We have a house that seems to get Indian Meal Moths every year for the last 3 years from March through fall and quits in winter. The attic seems to be the major area and they trickle into the inside of the house. Insulation in the attic prevents access to the entire attic because it is too low to crawl. There may have been squirrels in the attic soffit several years ago. I have dusted and fogged and no success. I have screened all roof vents with tight window screen and they still are present. No larvae or webbing are ever found anywhere except maybe 4 times in odd places with no food areas. The customer understands we are doing everything for him but is still upset that it continues. What advice do you have?

ANSWER:

It sounds like you do have a moth infestation within the home, perhaps the attic, and that it is just providing continuing generations of the moths from some food source they have found. Over time this would finally disappear on its own as that food source is finally depleted, but this could take awhile depending on how much food their is. Since the attic would cool down tremendously through the winter this also would slow down the rate of development of the larvae/pupae, and this could account for the seeming lack of activity those months. But, since these moths are capable of having many generations in a single food resource you may not be getting new adult moths coming in, but just adults from one generation mating and depositing eggs back on that food material.

The larvae of the IMM typically does leave the food resource and go wandering great distances from it looking for the perfect place to create their little cocoon and then pupate. This could account for finding them in areas of the home where they should not be, and long distances from whatever it is they are infesting. In an attic it may be rodent bait tossed there by the homeowner, and often people will "toss" bait blocks or packets to the far reaches of the attic without considering the future consequences of not being able to retrieve that bait. Rodent baits are not toxic to insects. It also may be food caches placed there by squirrels or other rodents, and if so these could be large quantities. Rats often steal pet foods and store them in inaccessible places - inaccessible to people but easily available to insects, and these could take many years to finally be consumed by the bugs.

So, there are all my explanations as to why you may be seeing this lingering infestation. Eliminating it is another question, but it boils down to a need to find the actual source of the problem and removing it permanently. Fogging and dusting would be superficial applications that are going to contact and kill some adult moths and some wandering larvae, but normally are ineffective at controlling the problem at its source. Even if you somehow killed all of the larvae on that food material, the material is still there and eventually will be discovered by new insects that are determined to recycle it. The best I can suggest is to make an even more thorough and detailed search of the attic to try to isolate the location of the food material.

Another possibility might be the use of one of the "mating disrupter" pheromones such as the Cidetrak IMM. These use large amounts of pheromones that cause the male moths not to be able to locate the females, and therefore be unable to mate. This can help to break up the continuing life cycles and stop the production of new moths. However, this does not stop the ultimate problem which is the presence of some food source in that area.

Another consideration is that the IMM will feed on a great many different kinds of foods, and I have seen them in homes feeding on dried-flower arrangements. They also get into pet foods, dried fruits, nuts stored in the garage, decorative arrangements in  boxes, etc. Anything that is grain or fruit based is subject to their activity, so you may do another inspection and look for other possible sources.

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