Insecticides favor pests

tomatoes with insecticide on them, pesticide treated tomatoes, tomatoes with seven on skin

Did you know that most insecticide treatments favor the pests? Though many gardeners believe the opposite, still, it’s true. The question is: “If insecticides kill pests, how can they also favor them?”

It’s important to see the garden as an “ecosphere.”

This means, that at least to some degree, it is an enclosed biological system. Of course it contains plants, but remember, the garden contains much more than the plants you put there. It contains other plants, which we sometimes refer to as “weeds.” It should also contain a whole lot of life. A healthy garden will probably host amphibians, reptiles, some mammals and birds as well as a host of invertebrates, both in the soil and above it. All these living things interact.

garden predator eating pest, robber fly eatiing stink bug, predatory fly
This is a robber fly eating a stink bug. Robber flies are voracious predators of garden pests

The relationship between predators and pests is especially important.

Some creatures eat your plants and some eat the ones that eat your plants. In an ideal situation, the predators keep the pests in control, so that you have a healthy, productive garden and a good harvest.

A healthy garden has both pests and predators in balance.

The predators keep the pests in line. The pests feed the predators. Without some pests, the predators leave or die out, making an opportunity for a population explosion of pests! Even if you had no pests in your garden, eventually some would arrive, and without the presence of beneficials, the pests multiply at an incredible rate.

Insecticides favor pests because they multiply MUCH more rapidly than do beneficials (predators).

It’s a fact, and herein lays the reason that insecticides favor pests. Most insecticides kill indiscriminately. The gardener sprays a crop, killing everything that lives under its cover. That’s everything, both beneficials and pests.

garden toad, Fowler's toad, garden predator
One toad will eat more pests in a summer than an application of pesticide. But if you need more toads, it takes nearly a year to produce them.

The insecticide may kill the beneficial outright, as is the case when one sprays their beans and we accidentally spray a robber fly or a praying mantis. Or, it may kill the beneficial when it eats the pest which falls, dying, to the ground (as happens to the toad).


praying mantis, beneficial insect
The praying mantis eats lots of garden pests.

Insecticides favor pests because, they kill both pests and beneficials and…

the pests’ population recovers much more rapidly.

When I was a boy our family garden was overrun with Mexican bean beetles, every summer. We waged war with Malathion and Sevin, often having to spray every week to ten days. In spite of our efforts, in some years our beans were devoured by the beetles. They simply reproduced too rapidly, as we had killed the beneficials while fighting the pests.

Later in life I learned my lesson. When Mexican bean beetles showed up in my garden, I hand picked them, dropping them into a can of water with some vegetable oil added. I also inspected the plants, squashing the eggs which I found hiding under the leaves. Within a few weeks, the bean beetle invasion petered out. My beneficials were alive and on duty. They were the “mop up crew.” But in future years, they did the job for me.

What can I do when I have an invasion of pests in my garden?

  • I can do nothing and wait for beneficials to arrive. This may cost me the crop, but with time, it will probably work (for future crops).
  • I can hand pick or selectively kill pests while I wait. Even though time consuming, this can really help.
  • I can order some beneficials from a reputable garden supplier.

Arbico Organics sells beneficial insects.

  • I can plant nectar producing crops, such as cowpeas, dill, buckwheat, sunflowers, mint, and other flowering plants. These help feed and attract beneficial insects. If I have them before I have a problem, it’s likely that some beneficials will be on hand when I need them.
  • Provide water and cover for some kinds of beneficials (such as toads, garter snakes, lizards and frogs).
  • Provide cover and water for birds. Even sparrows eat A LOT of insects.
  • If I absolutely feel obligated to spray, I can limit it to just the worst part of the infestation and use something which does not have a lingering toxicity.  Personally, I try to avoid this one.

Bug of the Week: Wheel Bug (One of my favorite beneficials)

Thread on Wheel Bugs: Green Country Seed Savers

Yard long beans not only provide a great vegetable but also loads of nectar to attract beneficials.



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2 thoughts on “Insecticides favor pests”

  1. wonderful article. This is our first year to have a decent garden. I’ve pretty much had a live and let live policy for pests this year. I just wanted to see what would happen. So far, so good. I try to plant a lot of companion plants such as basil with my tomatoes, marigolds, dill, etc. to help ward off pests, but also add variety to my garden.

    1. Variety is always a good thing! Eventually everyone encounters a serious garden pest, yet as a general rule it’s best not to use anything which kills both “the good guys” and “the bad guys.” Thanks for commenting, Christina!

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