Sunday, August 29, 2010

Grain or Meal Moth Infestation Out of Control - Help!

Indian meal moth trap catch
This question was sent to our 'Bugs site:

Briefly, the top floor of our small church building is simply full of grain moths (meal moths) and despite our best efforts, we seem to be losing the battle.
The problem came to light over a year ago, primarily in the kitchen. Problem areas were located and much work was done to clean everything in the area. Even at that time, traps were catching many, many moths (see photo) in areas that spread far from the kitchen. We did what we could, then the weather cooled and things seemed pretty quiet. We kept monitoring traps and replacing as needed, rarely seeing activity.
As the weather warmed in early summer, boy oh boy did we see a resurgence. Traps needed replacement as often as every 3 days. We continued to seek sources of infestation and clean, clean, clean. Then we realized our sanctuary -- a significant distance from the kitchen -- was heavily infested. Again, we've done what we can to clean and clean and clean. Sometimes we seem to be making progress, then another crop hatches as we feel back at "square one" as the saying goes.
We're basically monitoring and cleaning all areas of the top floor, and not making perceptible progress. Today we tipped over a piece of furniture and found the underside laden with worms, webs and eggs.
Other details:
  • Last year, in frustration, we had an extermination service spray. As you would guess, that was a waste of money.
  •  On the lower level of our building there is limited evidence of moths, though we have traps strategically placed.
  •  I am the coordinator of an emergency food pantry, located on the lower floor.  The pantry is not infested and was not a source of the problem.  We have mega monitoring in this area; it is closed off from everything else and was completely cleaned and painted within the past 2 months. Obviously my deepest concern is allowing the upstairs. problem to compromise the pantry and we're working hard to ensure that does not occur.
  •  It is my personal opinion that the moth problem began perhaps 2 or more years ago and no one noticed the problem quietly spreading far and wide.
Answer

The short answer is the primary moth infestation must be somewhere that is not obvious or you would have already found it. The larvae of these moths infest grains, seeds and other course material like cereal. A common and difficult-to-find source of moths is sometimes a cache of seeds/grain from a rodent nest inside the walls or ceiling. I agree that the moths are probably spreading out from this primary infestation to other parts of the building and I agree that it has probably been going on for awhile. I also agree that pest control is not the answer, unless they eliminate the rodents.

Pheromone traps (below) won't eliminate the moths but they may help to pinpoint the highest concentration and therefore where the primary infestation is located so definitely keep traps out. General cleaning won't help much either since these insects require a quantity  of seeds or grains not just crumbs. See Meal Moths & Traps for more information.

From your description of where you find moths I'd first suspect the second floor ceiling/attic space may be the source. Rodents often nest in these areas and will store seeds or grains. Your best bet, if I'm right, is to control and exclude the rodents, then the moths should go away. If you can actually find the nests, or caches of seeds/grains, and remove them the you'll speed things along.


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