Pest Control Part 1: What is a Pest?

Since I’m the resident entomologist on Biofortified, and because the main pests in almost all agricultural systems are insects it only makes sense for me to write something about pests and how they’re managed in agricultural situations. My role here on Biofortified is to write about the basic biology of pests, but I will be discussing management from time to time.

Ellipsidion australe: Cockroach? Yes Pest? No.

To say that insects are pests would be far too simplistic because of their sheer diversity. The two families of parasitoid wasps I’ve been discussing on the insects and pests information site, the Braconids and Ichneumonids consist of about 180,000 species together. If you want something to compare this to, there are roughly 10,000 mammalian species. There are a lot of insects around us, and they all have different ecological roles.
While some insects feed on crops, others feed exclusively on other insects which makes them the enemies of our enemies and thus…our friends. Even in a monoculture system, there are interactions between pest animals, their environment and people. Understanding these interactions is key to understanding things like why we need pesticides or why your town is inundated with ladybugs every year.
So…what, exactly constitutes a pest?

The most simple definition of a pest is an organism which pisses us off. That’s really it; the term is completely anthropocentric. Pests are creatures which interfere with our activities in any way, shape or form. In agricultural settings, insects cause damage in a variety of ways. The most common are the direct or indirect consumption of our goods such as a corn earworm or corn borer feeding on corn. There’s also the transmission of disease to livestock, plants and people. Some such as bed bugs feed on us directly and others like cockroaches share our dwellings and offend our sense of cleanliness. Others such as wasps or yellow jackets will inject us with harmful substances. Some like mosquitoes or aphids transmit diseases to us or our plants.
There are three very broad categories of pests which overlap: Medical/veterinary, urban and agricultural. Veterinary/medical and agricultural pests are fairly self explanatory; respectively they are insects which harm livestock and humans while agricultural pests harm crops. Urban pests are generally pests which infest our dwellings, although as I mentioned earlier there’s quite a bit of overlap between the categories.
Blattella germianica. Cockroach? Yes. Pest? One of the hardest to get rid of…

There are also natural enemies, the insects which feed on pests. A good example of natural enemies are the parasitoid wasps I’ve written about because they kill caterpillars which would normally eat our crops. There are several families of flies which feed on insects in a similar manner that parasitoid wasps do. There are also predatory insects which will help keep pest populations down.
There are also pollinators. Bees are a textbook example of this. Without bees, about 80% of the food we eat wouldn’t exist because they pollinate crops. No pollination, no fruit, nuts and other food crops. Even pollinators we don’t raise contribute millions of dollars to the economy every year.
Bear in mind, though, that there’s a lot of overlap between all of these categories. Whether an insect is a pest or whether it’s beneficial will depend solely on where it currently is, what it’s feeding on and what it’s interacting with.
Let’s use the example of the common insect family Meloidae as an example of how the term ‘pest’ and ‘natural enemy’ can almost paradoxically overlap. Some Meloid beetle larvae feed on grasshopper egg cases, which helps keep grasshopper populations down and reduces the amount of alfalfa lost through grasshopper damage. You’d think they’re a good thing to have around…and in some ways they are.
The problem comes when the adult beetles emerge. Meloid beetles are popularly known as ‘blister beetles’ because they produce a chemical called cantharadin which destroys skin and creates large, characteristic blisters. You can imagine how eating them would cause problems because cantharadin is incredibly toxic when ingested.
Herein lies the problem. Blister beetles are pests of alfalfa fields because alfalfa is fed to farm animals. You get a handful of beetles into a racehorse’s food and you’re out a multimillion dollar horse. Although they’re a good thing to have around as larvae, the adults are quite capable of killing animals as large as a horse. Some horse owners even take extreme measures to ensure the safety of their animals, sometimes buying feed from across the country to avoid any potential problems.
Ladybird beetles are another great example where this paradox comes into play. Ladybird beetles are prized in most agricultural situations because they consume aphids, which suck plants dry and transmit disease. They’re not prized in vineyards because they, too, secrete their own defensive compound in the form of bitter tasting alkaloids. They won’t kill you but even a small amount of ladybug can ruin very expensive wine by making it taste bad, which is known in the industry as Ladybug Taint.
They can also be urban pests, as anyone who lives in areas where asian ladybird beetles can be found. At the end of the growing season when food is scarce, the beetles look for places to overwinter. The best places are small cracks that allow high densities of ladybird beetles to congregate. Unfortunately for homeowners, they tend to find their way inside dwellings and become annoying uninvited houseguests.
Pest is a word that’s very simply defined. The problem is that a lot of the time, lines can be blurred depending on what you’re growing and the insect in question. Furthermore, a lot of the animals we consider pests play important roles in the environment. In the coming weeks, I’ll be talking more about the science of pest control and how it relates to agricultural settings.


  1. Excellent post! It can be really hard to remember that a given insect has value when you’re seeing it as a pest. I had no idea that it worked the other way around, where an insect that most people think has a lot of value actually is a pest in some situations. I’m willing to put up with ladybird beetles in my house over the winter as long as they keep eating aphids, but I might be less tolerant of them if they had the ability to ruin a product as valuable as wine that I was trying to make. I look forward to more writings from you about pest control. It’s such an important subject, especially when it comes to agriculture (including animal ag).

  2. Yeah…I should actually be thanking you. Your EGW post gave me a good jumping off point for the subject of pest control, which is exactly why we need pesticides. There’s also an economic aspect to pest control, and I’ll be discussing that in Part 2.

  3. Great post. As a pest control operator I’ve found that information about the important role of insects is not wide spread enough. Thank you for sharing – didn’t know that wasps keep the caterpillars in check.

  4. I have just become aware of your site, and I am impressed with those who post here. I know your primary issues deal with agriculture…at least for the few articles I have read, but I wonder if you would care to explore the concept of IPM and structural pest control.
    I maintain that IPM can only be explained scientifically in an agricultural context because IPM is based on threshold limits. If that is so, then there can be no such thing as IPM in structural pest control since the threshold limit for pests in one home or business is zero. Would you agree or disagree?

  5. Raleigh…both predatory and parasitoid wasps can do a good job keeping populations of various pests in check, but they still can outgrow their natural control measures. I’m working on a few posts about diseases in insects, as well.
    Rich, I’m actually in the process of working on a medical post but I’ve not been able to find any good sites which explain the life cycles of the organisms involved so I kind of have to make like three or four introductory posts first. It sucks, but I’d like to take it head on after a thorough introduction to the subject.
    As for threshold limits for urban pests, I think that’s a great question. It’s going to depend on the pest, the location and the people involved.
    Dumpster flies (Muscidae, Sarcophageidae and Calliphoridae), for example, provide a case where I think a threshold could be potentially set. If you have a dumpster set a certain distance away from the door of a restaurant, there’s probably a number of flies which would result in periodic invasion. Keep the flies below those levels (or just empty your damn dumpster every once and awhile), and you should be set. For places like poultry farms and hog confinements, there are thresholds which involve the point where the animals are too bothered to eat-but we’re getting back into agriculture even though the pests are the same.
    For some critters, like mosquitoes, I think a threshold can be set at the numbers where disease transmission occurs or merely where people are bothered. The former is relatively easy to measure, but the latter will depend on the people in the community. If you really want to be a dick, the economic threshold for disease vectoring mosquitoes is at the point where controlling mosquitoes is cheaper than treating the diseases they carry. I’d hope we would treat them long before that point, though.
    For others like termites, cockroaches, and bed bugs…I’d agree that no threshold can be set. Of course, this also leads to problems when these guys become resistant to pesticides because the number of pesticides which can treat these guys is relatively limited as I understand it. Treatments can get more expensive, risky and invasive as a result which may cause some people to simply live with the problem instead of getting it taken care of.
    I’d like to hear what you think, though. I’m a grad student who recently graduated with a BSc and despite a good knowledge base I don’t have any extensive experience in the field.

  6. Joe,
    My views on IPM are based on the original concept as presented in Hilgardia in 1959, i.e. as an agricultural concept based on economics. It became clear that it was impossible to eliminate pests in fields so threshold limits were set predicated on the idea that a certain number of pests would do a certain amount of damage, and it the amount of damage caused by pests exceeded the cost of pesticide applications then the fields would be sprayed. That is IPM. IPM can be scientifically defined in that context.
    The problem now is that so many are attempting to redefine IPM in ways that cannot be defined, or if you prefer, unending defined and redefined based on philosophy, not science. Anything involving the impact on human beings or animals and pests, cannot by the original definition, be IPM. Whether fewer pesticides are used, no pesticides are used or all pesticides are used it is not IPM if the threshold limit is zero.
    Whether it is flies or mosquitoes the threshold limit is zero when it involves human impact, and I agree with you that we must be concerned long before the numbers become large. Even though we know that in an uncontrolled environment a zero threshold limit is impossible to attain, that is still what IPM is based on.
    I maintain that there is no such thing as IPM in structural pest control as a result, and the only reason it exists is because the EPA and various state governments says it exists.
    Mechanical or structural exclusionary changes are not IPM. That has always been a part of pest control, although it wasn’t emphasized. Emphasizing it doesn’t make it IPM.
    Resistance is a natural component of pest control and is inherent to nature. Bed bugs are resistant to a host of pesticides, but not all pesticide categories. Cross resistance in pyrethroids is very real. They draw the same kind of immune response as DDT, and resistance to DDT started very early on. However, bed bugs are not resistant to carbamates, although in Australia they claim to be seeing resistance to bendiocarb (Ficam), and they show no resistance to organophosphates such as chlorpyriphos (Dursban) at all, we just don’t have them as tools any longer.
    I enjoyed your comments and will look forward to your next article. If interested you may wish to visit my blog. It is called Paradigms and Demographics. Just Google it with the spaces….it should come up first.
    Best wishes,

  7. I can only go by what I was taught, but in DoD Pest Controller training we learned the following:
    “Integrated Pest Management (IPM) offers a sustainable approach to managing pests by combining biological, cultural, physical, mechanical, and chemical tools in a way that minimizes economic, health, and environmental risks. IPM minimizes the use of chemical substances by utilizing routine monitoring to determine if pest control measures are necessary. IPM also employs educational methods to control pest populations. Application of least-toxic chemicals is used as a last resort. IPM can be used to control pests such as rodents, insects, fungi, weeds, and other vegetation, therefore reducing the use of rodenticides, insecticides, fungicides, and herbicides.
    “IPM often uses biological controls as a first defense. If non-toxic controls fail, carefully timed and targeted pesticides are used. These pesticides should be chemically targeted to the pest of concern; be chemically non-persistent in soil, air and water; be used only when needed; and be applied to as small an area as possible.”
    This quote is from the Joint Service Pollution Prevention Opportunity Handbook but I’ve seen similar in various Army and DoD manuals.
    Perhaps this isn’t the original definition of IPM but it’s certainly what is used today. This definition isn’t based on philosophy, but on sound science and economics. Minimizing chemicals used saves money. Using chemicals only when absolutely necessary reduces the risk of resistance.
    The idea of thresholds doesn’t have to be left out, though. It makes sense to have a certain level of infestation that can be considered below the action level, and it doesn’t necessarily have to be based on economics. I agree with Joe, we can have action levels that are based on health and nuisance.
    In my experience, no Dining Facility is going to have zero cockroaches, so the action level for pesticide isn’t necessarily 1 roach. When I was inspecting Dining Facilities, the first step was to work to eliminate food sources and to seal areas where pests might be entering the building or living. If we still see a few roaches, we might consider traps, and so on. The same applies for mosquitoes and flies. The action level will differ depending on the situation.

  8. Dear Anastasia,
    The quotes you cite are the usual stuff that can be found in all of the government handbooks promoting IPM, but the reality is quite different. Every state had to find its own definition for IPM in structural pest control, and in the process they wanted to make sure that they don’t come up with something that would interfere with IPM as an agricultural concept. I know this factually because I was part of the group that worked on this in my state.
    “Integrated Pest Management (IPM) offers a sustainable approach to managing pests by combining biological, cultural, physical, mechanical, and chemical tools in a way that minimizes economic, health, and environmental risks. IPM minimizes the use of chemical substances by utilizing routine monitoring to determine if pest control measures are necessary. IPM also employs educational methods to control pest populations. Application of least-toxic chemicals is used as a last resort. IPM can be used to control pests such as rodents, insects, fungi, weeds, and other vegetation, therefore reducing the use of rodenticides, insecticides, fungicides, and herbicides.
    “IPM often uses biological controls as a first defense. If non-toxic controls fail, carefully timed and targeted pesticides are used. These pesticides should be chemically targeted to the pest of concern; be chemically non-persistent in soil, air and water; be used only when needed; and be applied to as small an area as possible.”
    Most of that is great if there are no pests or are being used in an agricultural or landscape setting. I have accounts where I only monitor. That isn’t IPM. There are accounts that I apply pesticides on every trip. That isn’t IPM. I use every tool and technique available to our industry, including vacuuming, steam, dusts, liquids, caulking compounds, and I even repair access areas using mortar to seal off areas from rats, and drain gels for phorid fly control. That isn’t IPM.
    All this other stuff is claptrap, especially regarding biologicals. They have no place in structural pest control because they don’t work. Releasing wasps in structures to get rid of American cockroaches is non-workable as well as some of the even more exotic schemes presented over the last thirty years, including releasing peptides into a structural environment that would make cockroaches urinate themselves to death. Even if that had worked, it would not have been IPM.
    I am not opposed to the tools and techniques that are used in so-called IPM programs. These tools and techniques are what we have preached and practiced for 150 years. In the 1850’s there were ads in the New York newspapers advertising:
    “Pesticides such as phosphorus paste, arsenic, strychnine, cyanide, pyrethrum and a number of disinfecting compounds were available. In addition screening, netting, traps and fly paper were produced by American industry.”
    The names of those tools have changed, but the tools are the same. Liquids, powders, baits, traps cleaning up debris and trash, sealing up access and harborage areas, drying up wet areas along with trapping and netting, and yes…educating the consumer about what they need to do. These tools and techniques are 150 years old; just because we have added some new products such as IGR’s and some new baits that doesn’t make it some kind of brand new thing called IPM. That wasn’t IPM 150 years ago and it isn’t IPM today.
    IPM in agriculture can be defined because it has a basis for the definition; threshold limits based on economics. In structural pest control there are no action thresholds and the economics is still zero based. IPM in structural pest control is not based on science, because it has no basis for the any scientific definition as it does in agriculture. IPM in structural pest control is a philosophical concept with no hard scientific basis. The ability to redefine IPM in this context is unending as a result. That isn’t science, it is a philosophy disguised as a methodology.
    When Shay’s and others first outlined IPM in 1959 they noted that others were attempting to redefine IPM to mean anything they wanted it to mean, and this would undermine the value of it. He was right. IPM in structural pest control philosophical….it is not scientific. If IPM is ‘science’ in structural pest control then someone needs to tell me what it is?
    Who decided we needed something called IPM? The environmentalists and their allies in government who want pesticides banned as a long term goal; and universities who are desperate for government grant money. The most sure fire way to get grant money is to promote IPM. There was a time when the university extension departments were filled with pesticide users, believers and some were pesticide patent holders. That appears to have changed. They are retired and replaced with those that have become infused with the “litany” of the environmental movement. Grant money and environmental indoctrination has made many of them true believers. It would be interesting to see how the universities would react if the only grant money available was for the purpose of proving that IPM doesn’t exist.
    In summary, I object to using the term IPM, which needs to be eliminated from the lexicon of structural pest control terms, because I object to attempting the creation of something outside of traditional pest control called something other than pest control; something which cannot be defined because IPM in structural pest control has no scientific basis for a definition. I object to concept without form. I object to philosophical flavors of the day. I object to change for change sake. I object to the arrogance and propaganda of those promoting IPM in the universities and in government bureaucracies.
    Rich Kozlovich

  9. Rich,
    The worst reason to subscribe to a definition of a field is simply because it’s the original definition. Fields change over time because of new ideas. Some are good, some are bad…just like everything else. The reason thresholds are difficult to set in home settings is because the damage is based upon subjective, rather than objective means. The damage either can’t be measured reliably, or in the case of termites is essentially guaranteed to get to the point where the structure itself is in danger or unsellable.
    While I’d agree with you that it’s difficult or impossible to set thresholds for many household pests, that doesn’t mean that some places don’t end up setting their own thresholds out of sheer pragmatism. Try eliminating flies anywhere or smokybrown roaches anywhere in the south…it’s not going to happen. For this reason, management is key in these situations as it is anywhere else.
    I’d also disagree with your assessment that pests which afflict animals are not subject to IPM. We can measure biomass reduction as a result of red mites in poultry or stable flies in cattle, as well as hide quality reduction from warble flies and sheep ked. Lice and ticks are also subject to similar measures, and we can measure numbers which result in the transmission of disease. Epizootic diseases should also be able to be measured similarly (but not identically, of course) to crop reductions due to disease. Now, of course, biomass reduction can be a result of anemia or feeding disturbance but my point is that the result is real, it is measurable and it’s dependent on pest populations. This means that thresholds can be set using economic parameters.

  10. Dear Joe,
    When I first read your post I had to think about it for a while. I don’t think I can agree with the statement,
    “The worst reason to subscribe to a definition of a field is simply because it’s the original definition. Fields change over time because of new ideas. Some are good, some are bad…just like everything else.”
    Although the back half of that statement is absolutely true, It doesn’t justify the first half. Let me explain why I say that.
    Science has many of fields of study. Science is easily defined in the context of the first true science, chemistry, where the scientific method of experimentation and observation originated. Although chemistry was the first true field of science, that didn’t preclude other fields of study from being scientific fields of “science”. However, each of these fields, including chemistry, weren’t “science” they were components of what now makes up what is broadly called ‘science’. They became fields of study because they had a logical base from which to declare their area of expertise as a “field” of science and rightfully gave separate names to these fields of study.
    IPM isn’t presented in this manner; except in agricultural settings there is no logical basis for calling anything IPM in any other setting, including structural pest control. IPM is a practice that is s “form” of pest control with a logical basis for having a separate designation…i.e., threshold limits based on economics. One can say, “I practice IPM ” in an agriculture setting and everyone knows what that means. If one says, “I practice IPM” in a structural setting, no one really can be quite sure what that means because there is no logical basis for that statement.
    If threshold limits are the logical basis for IPM and pesticide use in agriculture setting, what is the logical basis for IPM in a structural setting to justify using that agricultural form of pest control in a structural setting? While structural pest control and agricultural pest control are components of pest control they are given these separate terms because they clearly are separate practices under the broad term of pest control. Even regulatory agencies make that distinction.
    The threshold limit is easy to set in a home or business. Just ask the homeowner or restaurateur! I can personally guarantee that its zero. That is the threshold limit in that setting. While I agree that it is impossible to guarantee that the zero threshold limit can be maintained at all times, it is the logical basis for “Structural Pest Management” or SPM if you will. (which just hit me, I think SPM is a great basis for a great article….this has been a good discussion and is leading me down another path of thought.)
    If IPM is to be a component of SPM it has to have some logical basis for use of that term. It can’t be borrowed from another field of pest control, redefined, and claim that it is IPM any more than zoology can be called biology or even chemistry. Each has components or each other, but there is a logical basis for each of these fields of science being defined separately. It can be “Reduced Pesticide Pest Management” (RPPM), or “No Pesticide Pest Management (NPPM), or “Exclusionary Pest Management” (EPM), Organic Pest Management (OPM) if they like, and then present their logic for justification to rename these efforts as a field of SPM in a structural setting. But it cannot be called IPM as there is no logical basis for IPM in a structural setting.
    Unless that rationale is philosophical; then if you wish you can call it Metaphysical Pest Control (MPM) and I won’t object.
    Normally I wouldn’t care how things are designated all that much except in this case it isn’t just nitpicking. IPM is being presented as an alternative to “traditional pest control” with the ultimate goal of eliminating pesticides. I feel that it is imperative that this issue must be vetted in its entirety. Believe me when I say that bed bugs are merely the tip of the iceberg.
    Thanks and best wishes,
    Rich Kozlovich

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