Myth: Pesticides Only Kill Bad Bugs

Can We Use Pesticides Without Harming Beneficial Bugs?

~ Do not draw your sword to kill a fly – Korean Proverb

Whether you’re wrangling with Japanese beetles munching on your flowers, slugs eating holes in your vegetables, or caterpillars feasting on your trees, it’s tempting to use pesticides to solve the problem. And it’s easy to forget that there’s more going on in your backyard ecosystem than meets the eye.

We often resort to pesticides to deal with garden pests. But pesticides don’t just control unwanted beetles and slugs. They often kill more than just the target nuisance, including beneficial natural predators like lady bugs. If a pesticide gets into your soil, it may also harm soil organisms that help to keep your plants healthy. There are many ways to control pests before resorting to pesticides.

FYI: Natural Solutions Really Can Work!

Pesticides define a broad category of products that are designed to prevent, kill, or reduce pests such as insects and mice. Pesticides also include products that control weeds, fungi, bacteria, and viruses. By their nature, pesticides present risk to animals, humans, and the environment because they are designed to harm living organisms. At the same time, pesticides are also useful to society because they help control disease-causing organisms, pests, invasive weeds, and insects.

U.S. Fish and Wildlife Service (USFWS) acknowledges the potential benefits of pesticides, but also monitors their potential impacts on the environment, including fisheries, birds, and threatened and endangered species. According to a recent U.S. Geological Survey study, pesticides were found over 90% of the time in streams, in more than 80% of fish sampled, and in 33% of major aquifers. USFWS also cites pesticide use as the likely cause of deformities and declines in amphibian populations as well as declines in species of pollinators and other beneficial insects.

The Problem

Bugs and other tiny creatures are all around us. But it is important to differentiate helpful insects from harmful ones. Many insects that we see are actually beneficial, such as butterflies, bees, ladybugs, lacewings, and fireflies. Butterflies and bees perform the important function of pollinating our crops and flowers, helping plants to reproduce. Ladybugs (technically Coccinellidae or Lady Beetles) and brown lacewings eat aphids, scale insects, mites, and insect eggs. Firefly larvae are predators of various insects, slugs, and snails.

Soils also are home to many beneficial organisms including bacteria, fungi, earthworms, ants, and beetles. Above ground, it is easy to see the plants, birds and bugs. But we don’t often think about the microorganisms that help keep our soils healthy. They’re vital to our backyard ecosystems just the same. Our plants draw their nitrogen from the soil, for example, and they count on beneficial soil bacteria and fungi to breakdown dead organic material (leaves, for instance) releasing ammonium and nitrate that a plant can easily absorb.

Beneficial bacteria and fungi also help control diseases that might otherwise run amok. They decompose dead animal and plant material into nutrient-rich, organic matter that helps your garden thrive. They even help the soil retain water. (For the record, bacteria and fungi are not doing this from the good of their little microbial hearts; breaking down dead material in the soil liberates the energy and nutrients they need to satisfy their own needs; their usefulness for the plants in your garden are an advantageous by-product) (Source: USDA Soil Biology Primer).

Unfortunately, pesticides may kill beneficial insects and other organisms right along with the bad.

In the soil, chemical pesticides may lead to unfavorable conditions. If pesticides are overused and seep into on the soil, they can harm insects and other living organisms that contribute to the health of your lawn. “Healthy soil is part of a functioning ecosystem and within the soil itself there is an ecosystem.” says Kim Stone of the Safer Pest Control Project, a non-profit Illinois agency. “The repeated use of pesticides may throw the soil ecosystem out of balance, by killing beneficial organisms that help keep the soil rich.”

Above the soil, pesticides create unwanted problems too. The use of broad spectrum pesticides sprayed all around the yard, rather than spot treatments on affected plants, can harm beneficial insects like ladybugs and lacewings. If pesticides drift onto plants that are attractive to bees and butterflies, these insects could be unintentionally killed.

The Solution

It’s natural to have a few bugs nibbling on your plants. If you keep your soil and your backyard ecosystem healthy, Mother Nature will normally keep things from getting out of hand. The discovery of one caterpillar in a row of thriving tomato plants is probably not a portent of doom. One possible solution is to expect and tolerate a certain amount of pest activity.

When control of pests is necessary, there are many options to choose from before resorting to pesticide. The best way to control pests is to head the problem off before it gets started. Plant a diversity of plants that bloom all summer. Many predators supplement their diets with pollen and nectar, so the same blossoms that make your garden beautiful will tend to attract the insect predators that you need to defend it (For more information see University of Illinois Extension horticulture article: “How to Attract Beneficial Insects to the Garden”). Plant some marigolds alongside those tomatoes and you’ll get more than just the splash of color. You’ll get protection, too.

Before you act, identify the insects you suspect are pests and understand how they can be controlled. The Illinois Natural History Survey website has helpful online ID cards with brief descriptions of beneficial and detrimental landscape insects and other organisms (“The Good Guys” and “The Bad Guys“), what they eat, and how to manage or encourage them.

You may find that you can control your particular pest with relatively non-toxic measures. Spraying pests off plants with a stream of water from a garden hose may be sufficient. For easily visible pests, like Japanese beetles, shake them into a cup of soapy water- which kills them without damaging the surrounding environment. Catch winged aphids, whiteflies, and leafhoppers with yellow sticky boards, which you can make yourself with yellow poster board and sticky glue. Even homemade garlic spray (15 crushed garlic cloves blended in one pint of water and strained) is effective against most insect pests.

If homemade solutions are not enough, you may need to use an organic pesticide. These include horticultural oils, insecticidal soaps and botanical insecticides. However, use organic pesticides in a targeted way in order to prevent unwanted consequences on other insects, birds, and soil microorganisms that are part of a healthy garden ecosystem. Fortunately, organic pesticide impacts are short-term because they tend to breakdown quickly and have no lasting impact on the environment. Other non-chemical pesticides are also an alternative. According to the U.S. Environmental Protection Agency, “Biologically-based pesticides, such as pheromones and microbial pesticides, are becoming increasingly popular and often are safer than traditional chemical pesticides”.

When no other solution is available, US Fish and Wildlife recommends careful use of chemical pesticides, to minimize impact on the environment: “It is important to use these products only when necessary (rather than on a regular schedule), use the minimum amount required to be effective, and to target application so that only the intended pest is affected.”

Many lawn fertilizers include pesticide, so if you do want to avoid adding pesticide to your soil you are better off also avoiding certain fertilizers — particularly those labeled as weed and feed. See EcoMyth’s articles from April 2010 on Fertilizer and May 2010 on Mulch for more information on alternatives to fertilizer.

Green Things You Can Do

  • Anticipate and accept some pest activity.
  • Attract natural predators and pollinators with a diverse and colorful garden.
  • When possible, use non-chemical practices to keep the lawn healthy and the ecosystem in balance.
    • Remove pests by hand or shake into a cup of soapy water
    • Spray pests off plants with the garden hose
    • Water adequately to keep plants healthy
    • Keep insects off plants and vegetables by using polyester row covers
    • Remove insect-damaged plants
    • Pull weeds and remove fallen leaves where insects can hide
  • Shop for natural lawn care products: A listing of Natural Lawn Care Product Suppliers in the Chicago Wilderness region is available from Safer Pest Control, a non-profit Illinois agency.
  • If pesticides are necessary, choose organic pesticides and those that are least toxic to non-pest species. Target pesticide applications to avoid water and non-target species. Avoid spraying in windy conditions.

Information in this publication is provided purely for educational purposes. No responsibility is assumed for any problems associated with the use of products or services mentioned. No endorsement of products or companies is intended, nor is criticism of unnamed products or companies implied.