Last updated: August 9, 2016 at 11:05 am

Pesticides include any substances used to kill, control or repel pests. We use pesticides almost every day, from ant and roach sprays for the kitchen, to weed killers for the lawn, mildew cleaners for the bathroom and mosquito repellents outdoors. Pesticides have become a widely accepted way to keep our homes and gardens relatively pest-free. About 85% of all American households keep at least one pesticide in storage.

Despite our willingness to use them, most consumers associate pesticides with pollution, health risks and toxic chemicals. Surveys show that about 75% of consumers are wary of using pesticides in the home. Many people today are avoiding certain synthetic (man-made) pesticides in favor of natural or “organic” products. But regardless of whether a substance comes from natural or artificial sources, if it controls pests, it’s a pesticide. And as long as pests are around, chances are that we will use pesticides.

There are many types of pesticides. Insecticides are pesticides designed to control insects. Herbicides are pesticides designed to kill weeds. There are dozens of others. In this f@ctsheet we will learn about the different kinds of insecticides and how to choose the right one for the job.

Choosing the right formulation

The first decision to make when selecting a pesticide is what formulation to use. A formulation is the way the pesticide active ingredient is mixed with inert ingredients to make it convenient and effective to use. Factors that influence the choice of formulation include cost, convenience in mixing and use, effectiveness against your target pest and safety. The following table describes the most important types of insecticide formulations and how they should be used.

Common types of pesticides

One way to think of pesticides is as low-impact or as conventional. Low impact products include those that are low in toxicity to people and pets (i.e., meets EPA Category IV standards) and have minimal impact on the environment, including beneficial insects. This classification is somewhat subjective, but still provides a useful way to select pesticides that meet most people’s definition of green or safer.  Some, but not all, low-impact pesticides may be classified as “organic.” Some organic products may not be considered low-impact if they are highly toxic. Here are a few examples of common low-impact insecticides that are widely available in hardware stores and garden centers.

Table 2. Classification of low impact insecticides, with examples.

Conventional insecticides include pesticides that are not considered low-impact because they are more likely to be hazardous to humans or pets (without careful attention to standard safety practices and following the label), or because they may impact beneficial insects or the environment even when used according to the label. Most of the products listed below have the potential to harm at least some beneficial insects and for this reason should be used when cost-effective, low-impact products will not adequately control the pest.

Just because a product carries the potential for harm, does not mean it cannot be used safely. Conventional pesticides include many useful and effective products that can be used safely by most gardeners. However, it is especially important to follow label safety directions when using conventional pesticides. Here are some of the common types of conventional insecticides.

Table 3. Classification of conventional insecticides, with examples.

Organic vs. Synthetic pesticides

In recent years a growing number of pesticide products advertised as “organic” have become available to consumers. To be considered organic a pesticide must be composed of only naturally occurring substances. Advertizers and others commonly imply that organic pesticides are safer and more environmentally desireable than synthetic products. While this may be true in some cases, there is no guarantee that natural substances are inherently safer than synthetic pesticides.

Organic pesticides usually consist of plant extracts with insect-killing or repelling properties. Plants produce many chemical compounds to protect themselves from diseases, insects and other threats. From a toxicology perspective, there is no difference between plant-derived pest control compounds and man-made pesticides. Both are chemicals. Both have some effect on the physical structure, development or metabolism of insects. And both organic and synthetic pesticides can be toxic to humans.

Most commonly sold “organic” insecticides, however, are reasonably low in toxicity and break down quickly upon exposure to water and sunlight. Their ability to degrade quickly and their relatively low toxicity is why botanical insecticides are usually classified as low-impact. However, there are exceptions. Rotenone, for example, is a popular insecticide with many gardeners because it is organic, effective in controlling many chewing pests and does not leave long-lasting residues on plants. In its concentrated form, however, rotenone is more toxic than many conventional insecticide active ingredients.

Don’t be misled by sales claims for many so-called “natural” products. Advertising which claims that any insecticide is “safe”, “pure”, “all-natural”, “EPA-approved”, “pesticide-free” and “chemical free” are at best misleading; and at worst, false and/or illegal. Many people get great satisfaction from using only substances found in nature in their garden. This is generally a good thing. However, use of synthetic pesticides can also be a safe and environmentally sound practice if practiced with care and discretion.

For more information

For more extensive information about the toxicology and safe use of pesticides visit the EPA-funded, National Pesticide Information Center at http://npic.orst.edu

Author:

Michael Merchant, Ph.D., Professor and Extension Urban Entomologist, Texas AgriLife Extension Center at Dallas