• Chelle Hartzer

Let Nature Take Its Course (AKA: How much is "acceptable"?)

In my position, I am constantly researching new information on pests. I also have many alerts on keywords that relate to pest control so I can find out what’s going on in the non-academic world. That means I occasionally get things like this:


Let’s back up just a minute. IPM is about using all the tools we can to deal with pest issues and attempting to get to the root of the pest problem to deal with it at the source. In the wider world of pest control (including agriculture, veterinary, greenhouse, etc.) many tools can be used. Using parasitic wasps, natural predators, and even fungus are options along with inspections, sanitation, trapping, and pesticides. For example, in a field of corn, it is okay to have a certain number of corn earworm because below that number, the monetary damage they cause is less than the cost of treatment. In a livestock area, it’s great to add in parasitic wasps that attack the flies attacking the cattle. It won’t eliminate them, but it will reduce the numbers. This process of “how many are okay” is usually referred to as the economic injury level (EIL).

In urban pest control, there is a slightly different situation. How many cockroaches are okay to have in a restaurant before it needs treatment? I think most of us would say none! How many bed bugs are okay to have in a house? I would guess most homeowners would say none! Would you be okay with one fly baked into your morning doughnut? Are less than five rodents okay in a grocery store? Are you cool with less than twenty ants crawling through your house? No, no, and no.


The EIL for most urban pests is one. This means that “letting nature take its course”, isn’t going to resonate with the customers calling up saying they have a pest issue. They want something done now. They want the problem eliminated. I once had a cereal plant ask me about releasing parasitic wasps to help control the stored product pest issue they were having. I asked them if their customers would be okay with finding dead (or living!) wasps in their breakfast cereal. Of course not.


It's not just releasing another insect into a contained space that is an issue. Parasitic wasps and other natural predators can never eliminate a pest population. Think about it this way:

You have a pest


You release parasitic wasps


Wasps attack pests



… but they can never get to every single individual pest


Wasps develop and kill pests they have infected.


They emerge and look for more pests, the cycle repeats.


If there are no more pests (impossible really), the wasps would die out. What will happen is the system eventually reaches an equilibrium where there are always some pests and always some predators. In the case of this article, sure: the hawk can kill a snake. It can never kill all the snakes in the area.


Then there is my favorite “natural” remedy: cats. I have written about this numerous times, you can find the latest here. Spoiler alert: they don’t work.


Betsy, outside doing her thing

Does that mean that as urban pest control professionals we can’t use economic injury levels or predators to combat our urban pests? We absolutely can. Particularly in outdoor situations, encouraging native predators to keep pest populations in check is a great idea. I typically leave as many web-building spiders around my home as I can to reduce the mosquito population. There will be natural predators and parasites outside that are bringing down populations of flies, cockroaches, and more. That’s why treatments should be targeted to specific areas to prevent those predators from getting knocked down with the pests.





We get in all the tight spaces!

However, the minute I see some ants inside my house, I’m not waiting until I see ten or twenty, I’m going to be doing something right away to deal with that. Letting nature take its course sounds great, but customers are calling because they have a problem they want dealt with (often yesterday!) so “nature” has had a chance and failed. Pest control professionals are nature’s superheroes, here to help out.


And if you want help with any of your “natural” pest problems and how to get to the root to solve them, contact us, we can help!


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