Webster’s Collegiate Thesaurus identifies a “pest” as an annoyance, offering up useful idioms such as pain in the neck, pea in the shoe, and thorn in the flesh. The American Heritage Dictionary takes it one step further and adds “harmful” or “injurious” to the definition:  Pest  n. 1.  An annoying person or thing; a nuisance. 2. An injurious plant or animal, especially one harmful to human beings.

In the pest control business, pests are not just unwanted insects and spiders —  rodents, birds, other animals and arthropods, even some beautiful flowering plants can be pestiferous “weeds.” We’re well aware that what might be a pest to one person may not be a pest to another. It’s all in the eye (and attitude) of the beholder.

PEST? IT DEPENDS ON INDIVIDUAL TOLERANCE LEVEL

Some people may not tolerate any kind of pest in their home, no way, no how. Sometimes potential pests only become pests at a certain level of pestiness. For example, most people can tolerate a single house fly, or even two, in their home but when there are suddenly 30 house flies buzzing about inside, the perception changes and they begin to take steps to control this new pest. Classical integrated pest management programs actually have a name for this – the “action threshold.”

In agricultural pest control, and even sometimes in urban pest management, the action threshold is the point at which control methods are undertaken. In other words, a particular pest can be tolerated until, and if, its numbers reach the action threshold. Above the action threshold, the insect, rodent, or other pest can be expected to cause unacceptable damage or irritation. This action level is different for each pest, each situation, and often each individual.

When it comes to pest control around homes and buildings, the action threshold rarely applies because we assume that when a person contacts an exterminator, they have already made the determination that the pest in question is at an unacceptable level for them. One mouse in the house is one too many for most people. Action levels may be higher for certain insects such as fruit flies but might be set at 0 for blood-sucking bed bugs or poisonous black widow spiders. On the other hand, if the presence of one mouse, or 5 cockroaches, or 3 spiders does not bother an individual, it is not a pest in their eyes and they are not likely to take control action at all.

PEST? IT DEPENDS ON TIME AND PLACE

Insects or other creatures may be considered to be pests in some situations but not in others. It’s all about being in the wrong place at the wrong time. We may be perfectly happy to see bats hunting insects in our backyard but we don’t want them roosting in our attic, beneficial or not. Likewise, the lady beetle is beneficial and a friend of children everywhere and we’ve been taught to appreciate this harmless outdoor insect. In recent years, however, we have been inundated with the invasive, multicolored Asian lady beetle that can move into homes by the hundreds to spend the winter, still relatively harmless but now a pest. A weed is often just a plant in the wrong place…a pest.

Photo Credit : By D. Sharon Pruitt from Hill Air Force Base, Utah, USA – Ants On Cheese, CC BY 2.0, Link