Insect pest populations can go undetected for decades before they become visible in tremendous numbers. That’s particularly true for pests like webbing clothes moths (Tineola bisselliella) and furniture carpet beetles (Anthrenus flavipes).
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A bank located in a high-end area of lower Manhattan had a noticeable clothes moth problem where employees worked in a large open room. While this situation occurred before clothes moth traps were commercially available, there were so many moths around that you did not need traps for proof.
We first suspected old, upholstered chairs in an adjacent area as the source, but inspection revealed no evidence or signs of clothes moths.
The bank manager was really upset, because he recently had all the carpeting ripped out of the problem room at great expense. Yet the clothes moths continued to persist.
With nothing found after an inspection, I sat in the main room to observe the occasional clothes moth flutter by. Because the moths are weak flyers, I knew there had to be a breeding source somewhere close by.
Then it hit me! Throughout the room were 40 to 50 large metal filing cabinets. I pulled out the bottom drawer of one as far as I could and peered behind the drawer. You guessed it: Inside were clothes moths and old carpeting.
▶ Solution: We first performed a space treatment on the void behind the drawers and the old carpet to knock down any live moths. We then removed all the old carpeting under the cabinets and immediately placed the remnants into large plastic bags as we went along. We sealed the bags as soon as they filled, so no moths had time to escape.
▶ Conclusion: Today, of course, we could have found the problem sooner with pheromone traps placed near the cabinets. Still, this is an example of where the client thinks the harborage was removed, but in reality, it was not. That part of pest management continues today despite our best efforts.
At least they weren’t bookworms
Furniture carpet beetle larvae suddenly were found crawling over books and the floor in a college bookstore. The building was about 60 years old, with no carpets or furs around. No bird or rodent problems were noted that might have accounted for a food source for the beetle larvae.
“What was the store initially used for when it was built?” I asked. “What else besides books was stored in this building?”
No one knew the answers.
During our search to find the source, we pried off a baseboard and found numerous live carpet beetle larvae. Apparently, to save money, the insulation originally stuffed in one wall was an old mattress stuffed with horse hair. The beetles had likely been there for decades. When the population was so high that they had to leave that environment, well, out they came.
▶ Solution: We opened the wall, removed the mattresses and vacuumed the area. We then applied a residual to destroy any larvae we might have missed.
▶ Conclusion: You have to keep asking questions until you get the right answers. And if the answers aren’t coming, you’ve got to keep inspecting. I suspect that eventually, the lack of a proper food source and the buildup of beetle fecal material drove the beetle larvae out.
Dr. Frishman, a PMP Hall of Famer (Class of 2002), can be reached at PMPEditor@northcoastmedia.net.
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