What is an infestation?

The first time a maintenance technician asked me what evidence qualified as an infestation, it didn’t immediately strike me as difficult to answer. But as I paused to go through the Rolodex of pests in my brain, I realized that I couldn’t answer his question with confidence.

My first thought was, “An infestation is a breeding population of insects.” Adult male and female pests with access to food, water, and a place to hide that could find each other and make babies.

But the scientist in me tends to complicate these simple matters by asking questions. What if there is one viable cockroach egg case containing over 30 eggs? If those eggs hatch in the right location, the nymphs could grow to adults and breed. What if there are two bed bug eggs? Those could be a male and a female that could reach adulthood. But the reality of one couple starting what we think of as an infestation is… We don’t really know for a lot of pests. What about one mouse? What if it’s a pregnant female? How would you know from the furry blur that runs along the wall? I could keep going…

Integrated pest management programs can often avoid this difficult topic by setting action thresholds—the number of live pests or certain set of evidence that warrants further action. In agricultural settings, the action threshold is often based on the amount of damage done to the crop. Maryland Department of Agriculture's publication details action thresholds for various pests in schools (which are similar to housing buildings).

In both schools and housing, our tolerance is low when it comes to public health pests. For these pests, we take some sort of action (not necessarily chemical) when one live pest is seen. One cockroach can produce enough allergens to trigger an asthma attack in a sensitive individual. We scale the response to the level of infestation. There’s that “infestation” word again…

Defining what an infestation is can be a fun science discussion. But if you’re a housing inspector or preparing for a Real Estate Assessment Center (REAC) inspection, you need an answer. I was recently informed that there is one for cockroaches and I wanted to make sure everyone was aware of the change.

Effective September 4, 2012, the REAC definition of “Infestation” is clarified with regards to roaches:

“When either one dead roach or only roach droppings is observed in a Unit or in an inspectable item location in Common Areas (e.g., halls/corridor/stairs, laundry room, lobby office etc.), the inspector is to record this observation as Health and Safety, Hazards, Other, and in the comment field write either ‘One dead roach’ or ‘Roach droppings only.’ 

When more than one dead roach is observed in a Unit or in an inspectable item location in Common Areas (e.g., halls/corridor/stairs, laundry room. lobby office, etc.), the inspector is to record this observation as ‘Infestation.’

When the inspector observes one or more live roaches in a Unit or in an inspectable item location in Common Areas (e.g., halls/corridor/stairs, laundry room. lobby office, etc.), the inspector is to record this observation as ‘Infestation.’

Revision #1, effective September 4, 2012, is a new provision and will be added to Part II: Definition Clarifications, Page 33, Health and Safety, as a new Item ‘E. Infestation.’ The Index will be updated accordingly.”

From: http://portal.hud.gov/hudportal/documents/huddoc?id=Comp_Bulletin_Rev2-3.pdf

These revisions are to supplement the existing Uniform Physical Condition Standards (UPCS) guidance which can be found in the Physical Inspector’s Field Guide:

[Images used with permission from American Property Consultants, Inc.]

Other notices that are applicable to housing and pertinent to pest control are:

• Promotion of IPM as an environmentally-sound, and effective means to address a major resident concern
• HUD Office of Housing's Notice on Bed Bugs
• HUD Office of Public and Indian Housing Notice on Bed Bugs

Comments

[KaciBuhl]

Interesting topic! It's also an important definition for homeowners trying to set their own action thresholds. When is it time to act? I think you're right; it depends on the pest species and situational factors. Are there sensitive people living in the structure? Is there a public health risk?

[Don]

One dead roach is NOT an infestation....yet one live Roach IS an infestation? Wasn't the dead roach ALIVE at one point in the area? So, at what point does the live roach turning into the dead roach go from infestation to non-infestation? A roach runs in under a door from the outside. Infestation? Or, just a single roach in the room? A person steps on the roach. No infestation? Just before it gets stepped on, it drops an egg case with 30+ nymph in-stars......dead roach but active roach egg case. Infestation? INFESTATION refers to the state of being NUMEROUSLY overrun or invaded by insects or animals in LARGE numbers as to cause damage or disease......Wikipedia, American English, Oxford. One "bug" is NOT an INFESTATION!

[Dennise Belmaker, StopPests in Housing]

Don, this can be indeed a confusing and gray area when dealing with pests - even for professionals. And that's the point we wanted to convey with this article. In most cases, you probably can't tell if that dead cockroach has been dead for days/weeks, or someone stepped on it earlier today. And for that matter, whether or not it left a viable egg case in the kitchen before dying... However, we all need to make certain decisions when it comes to choosing our course of action.
You probably wouldn't treat a 1 bug sighting the same as dozens of critters crawling up your walls, right? But also, as we've mentioned before, this will depend on who lives in your home - is there an infant, or someone with asthma? As surprising as it may sound, yes, even one cockroach can trigger an asthma attack! To make things even more complicated, most people wouldn't care about 1 ant as they care about 1 mouse or rat... so it also depends on which pest(s) you're dealing with.
When it comes to public health pests (e.g. cockroaches, rodents, bed bugs), not only we have a much lower tolerance, but it can be critical to have some clear thresholds to guide our decisions and actions towards an effective solution. This becomes even more important for organizations such as housing authorities, regulatory institutions, or pest control companies, that perform inspections and work under very specific policies, contracts, and procedures. These folks use numbers and other types of measurements every day to decide what treatment to apply, how much, how often, and so on.
The definition and thresholds for infestation in the pest management world are all but 'set in stone', they rather vary based on various factors (as alluded here) and interpretation. However, researchers and different organizations - like HUD, EPA and others - continue to work hard to create better protocols, including clearer thresholds and action levels.
~Dennise

[KF]

I found info on Orkin's site that seems reasonable. Finding a live cockroach during the day, droppings, smells or egg cases would be a clear sign of an infestation to me.
http://www.orkin.com/cockroaches/signs-of-cockroach-infestation/

[Dennise Belmaker, StopPests in Housing]

Thanks for sharing, KF. Yes, those would be typical signs of a roach infestation. For more information on how to recognize and address cockroach and other pests issues, check out the Pest Solutions page on our website: http://www.stoppests.org/pest-solutions/