Building A Better Mouse Triangle

The Old Pest Triangle

I'm sorry, but it's time to update our thinking about the old "pest triangle".

You may have seen the old "pest triangle". It has been around for years. You will often find it in training manuals and power point presentations across the country. It is meant to represent what a pest needs to survive and become a problem within a structure. The theory goes that by exerting control over one of the three corners of the triangle you can collapse the pest problem.

Unfortunately, this model really only accounts for the survival and potential reproduction of pests within a structure. Don't believe me? What element of this pest triangle solves for a mouse entering from an open door? Or flies entering around a damaged window screen? Spiders Ballooning onto a structure?

In each of these cases, controlling the availability of food, water or harborage would do nothing to prevent or control these issues.

We Need a New Triangle

I've never much cared for this pest triangle. I have always felt that it doesn't represent the whole story all that well. Instead, I teach one of my own design.

After many years of contemplating my successes and failures battling pest activity within structures, I started to recognize that in nearly all of my successes, I was able to make impactful changes across at least one of three distinct dimensions. These formed the foundation of my new model.

Resources

I combine food and water into "resources" because food and water are not the only materials many pests require. Wood pulp for wasp nests. Insulation for rodent nests. Organic material for the cases of case making clothes moths. These are all essential resources that, if not obtained in appropriate quality and quantity, the organism will likely not survive or reproduce.

Resource control is what you are recommending every time you ask someone to clean their kitchen, put food in pest proof containers, recommend cleaning a dumpster or trash container, clean up clutter, etc.

Habitat

I change "Harborage" into habitat. (I also like the term "micro-environment")

To me "harborage" is a place to hide or rest. This is essential, no doubt, but for the organism to thrive, the harborage must be located within, or create, an acceptable habitat.

Stacked cardboard makes for excellent harborage for German Roaches. Stacked cardboard in an area of ultra low humidity, excessive dust and a constant breeze makes for an extremely poor habitat.

?? In fact, we have demonstrated in our Urban Entomology Lab that by only adjusting the humidity within a habitat, we can eliminate German Roaches.

Access

Finally, and most importantly, a pest MUST be able to gain access! You can have ideal habitat with plenty of resources and if an organism is not introduced to the location as a captive or volunteer, no pest problem will develop.

Exclusion is the most commonly practiced method of access control for pests. Sealing gaps and penetrations into a structure is essential for long term control.

The more difficult to control access issues tend to center around human activity and pest entering as captives. This is where a pest is transported to a new location via human activity. This is Bed Bugs hitch hiking home on a persons luggage. A house mouse catching a ride on a pallet from a food plant to a distribution warehouse. Moths infesting a wool rug being moved from the basement to a storage unit.

In Practice

With this new model in mind, we can then look for choke points where small modifications to structure or behavior can generate outsized results. Focus on Access, Habitat and Resource control first.

Often, complete control over any of these three elements is impractical if not impossible. The trick is to find where, with the least amount of disruption, you can have the greatest impact.

The exact nature of the activities or modifications necessary are dependent upon the specific opportunities provided by the location and the biology of the pest in question. The types of changes that would impact a German Roach, may have no effect on the life of a House Mouse. Likewise, the actions that are possible in a commercial kitchen may not be practical in a residential kitchen. The key is in understanding the service site and applying the biology of the target pest to the given scenario.