By: Timothy Best, ACE, BCE

Being an entomologist and PMP in New York City, I often find that many folks assume my days are spent crawling through the city’s underbelly steeped in a battle against hordes of Norway rats, or that I am waist-deep in American cockroach infestations. While some days that sentiment may be correct, more often than not, I am actually out in the field tackling what I consider to be a much larger but definitely lesser-known problem with an adversary of a much smaller size: the black carpet beetle.

An Overlooked Pest

The black carpet beetle, Attagenus unicolor, is arguably the most ubiquitous and likely most destructive species of carpet beetle in the United States. Despite this fact, it garners little attention, as these insects are not widely considered pests of medical importance. While some research indicates that individuals living in close association to these pests may suffer varying allergic reactions from exposure to cast skins or beetle fragments, the black carpet beetle primarily remains a nuisance insect pest.

It is worth noting, however, that economically, the black carpet beetle, owing to its exceptionally diverse diet, can infest and damage everything from plant-based products such as stored grains to common household fabrics such as wool, resulting in significant losses. While not the norm, the black carpet beetle also may attack synthetic fibers, meaning those not derived from animal matter or containing keratin (the primary protein found in animal hair). Black carpet beetles are often free living in outdoor environments but will quickly invade structures, as they are attracted to light (the adults can fly) and, more importantly, to the presence of food and favorable living conditions inside buildings.

Life Cycle

The black carpet beetle presents many challenges, not just because of the diversity of its diet, which also lends itself to diversity in larval habitat, but because of its often-lengthy life cycle. Females will lay about 50 eggs in their lifetime, which will hatch anywhere from six to 10 days later. Eggs may be deposited in a multitude of locations, but always in areas near a likely larval food source, often in areas out of plain view. The larva will continue to grow as they progress through anywhere from five to 11 molts, leaving behind their cast skins each time. The larvae will continue to feed until they have enough energy to pupate. Pupation varies but typically ranges from six to 24 days before an adult emerges.

While on average the black carpet beetle completes its life cycle from egg to adult in about 11 months, with adults living between 30-60 days, there are instances where under favorable environmental conditions that cycle can extend to upwards of 24 months. So, it is often possible that larvae (the damaging stage of this insect) may continue to feed for anywhere from nine to 20 months. The black carpet beetle’s combined abilities of locating food in overlooked places and spreading broadly throughout a building makes its control difficult, to say the least.

Management

Successful control should not be confused with or interpreted to mean elimination, which rarely occurs. Control of black carpet beetles should start by considering a more longitudinal or long-term approach. A longitudinal approach takes into consideration this insect pest’s unique life cycle, diet complexities and varying and available habitats. So, what does that really mean? It means offering (when possible) a service that is recurring and avoiding a quick one-off service with a limited warranty window.

A one-time service equals short-term control. Rendering a single service, or even multiple services within the context of, say, a 30-day agreement window, is only going to be marginally effective. Depending on what methods you employ, it is likely that new broods will emerge or newly introduced individuals will establish themselves after the agreement period ends. Many times, this leads to client complaints about ineffective service after the fact.

Recurring services with frequencies at intervals varying from monthly to bimonthly or quarterly are a better approach, as they allow you stay just slightly ahead of emerging broods or newly introduced individuals. A recurring service aims to stay ahead of these population growth curves and generational cycles (typically one generation per year).

So, if you have ever experienced failures with black carpet beetles in the past, it may not have been your methods, per se, but your approach and a lack of longitudinal management. The true value of a quality carpet beetle management program should not be underscored or driven solely by price, but more so by anticipated outcomes. Philosophically, I am not averse to one-time services; they do have their place. I am just encouraging a sounder approach to black carpet beetles. Being able to articulate these points and provide a crash-course on black carpet beetle biology to clients may help you get more robust buy-in and cooperation. Educated and engaged clients make the best clients, in my opinion.

Integrated Your Approach

There are any number of methods, materials and approaches to black carpet beetle management, but to truly be successful, you must integrate a number of components. Always start with an inspection. Inspections should be resource-focused and not just a cursory look with a flashlight. Where are the likely food sources? Where are the undisturbed harborages? Ask yourself, “If I were a black carpet beetle in this environment, how would I survive?” The very basic tenets of IPM postulate that for any pest problem we are dealing with, if we can successfully find and modify the pest’s habitat (remove food, water and shelter), then we can greatly impact and influence the pest’s ability to survive. Find the resources, determine causation, and then solve the problem. Here are tips for control:

1. Interview the client and ask questions regarding sightings, damaged goods, products infested, clothing and furnishings. This can be used to better inform your inspection.
2. Identify the species. It is also very useful to learn and to be able to identify these insects not just in their adult stage, but also as larva and by what cast skins look like. By knowing the species, you can better research and understand its biology and habitat. Then, go on the hunt for the resources.
3. Work to cause these pests stress. What resources or conducive conditions did you find during your inspection, and how can you modify or eliminate them? By reducing the resources needed for their survival first, you will increase your overall treatment efficacy.
4. Treatment. Simply put, it cannot simply consist of an interior perimeter treatment with a residual insecticide. Applications, regardless of chosen formulation, need to be targeted to these pests’ harborage areas.
5. Use an appropriately labeled insect growth regulator (IGR). Research and science indicate the use of an IGR can significantly disrupt life cycles of dermestids. This is population management.
6. Engage and educate the client in their shared responsibilities. It is absolutely critical that clients work to eliminate (or reduce as much as possible) accumulations of lint, hair, dust and other debris that could serve as food for carpet beetles. Regular and thorough cleaning of rugs, draperies, upholstered furniture, closets and other locations where carpet beetles congregate is important to prevent and control these pests. Frequent, thorough vacuuming is an effective way of removing not only the food sources but also carpet beetle eggs, larvae and adults. Vacuums should be a go-to tool for PMPs. Instead of just applying a material next time, think about vacuuming first.

Black carpet beetle control is ultimately about creating a partnership between the pest management provider and the client. Offering an integrated service on a regular basis, combined with client education and engagement in source reduction activities, will offer broader, more substantial and lasting results.

 

Timothy Best, A.C.E., B.C.E., is the technical manager for Terminix Commercial, a sister brand of Copesan. 

This Tech Talk article was originally published in the August 2021 edition of PCT magazine.