Controlling Those Critters: How to Use Pesticides Safely

By Danny Klittich
Published: November 1, 2014 | Last updated: May 4, 2021 10:55:36
Key Takeaways

Danny Klittich and Bob Starnes share some tips to help you wade through the plethora of products available and answer some common questions people have about pesticides to help you determine what you should be spraying.

Source: Mhlam/

Pesticides are broadly defined as any material used with the intention of controlling and managing a pest. Annual global pesticide sales are in the billions of dollars, and the number of different pesticides available at garden centers can be overwhelming.


The assortment of brightly colored bottles and pictures of pests crawling off the labels are eye-catching, but how do you compare multiple products that claim to kill the same thing? How do you know how hazardous to human health each product is? What does it really kill? How long does it work?

How long after application should you wait to harvest the plant? All of these questions can be answered somewhere on the label, but this article will discuss some simple aspects of pesticides that you can discern just from looking at the front of the bottle. We will also share some safety advice and resources that will help you learn more about what you are spraying or what you should be spraying.


Types of Pesticides

The word pesticide can be used to describe literally anything you intend to use to kill something. This includes materials such as rubbing alcohol, hand soap, bleach and even a high-pressure spray of water. Because of this broad definition, we often refer to pesticides by their target. For example, pesticides that target insects are insecticides, products that target weeds are herbicides and materials that target plant pathogens are fungicides, just to name a few.

Pesticides are further classified based on their mode of action, or the specific way in which a product kills the target pest. For example, horticultural oil suffocates the insect, Bacillus thuringiensis (Bt) is a stomach poison and neonicotinoids are neuro-active insecticides. Many products act on specific physiological pathways within the target organism and, like the neonicotinoids, have more complicated modes of action.

The mode of action is extremely important to know if you are applying pesticides repeatedly to a crop. It is possible for the pest to develop resistance to a single mode of action. For this reason you should always rotate your pesticides between multiple modes of action.


If you would like to learn more about different modes of action or find out what mode of action a product is, the Insecticide Resistant Action Committee website, an international organization devoted to reducing pesticide resistance, has all the details. The site also lists all insecticides by active ingredient and where they fall by mode of action to enable you to rotate products appropriately. There are many examples of pesticide-resistant pests, from whiteflies to weeds, and this is an important issue in a production setting as well as at home.

Breaking Down the Labels of Your Pesticides

The pesticide label is a federally regulated legal document that is required to be on every container of product sold. There are different registrations for agricultural versus home use and there can also be state-mandated labeling rules on top of that. California, Washington and New York have some of the strictest pesticide labeling laws and regulations, and many pesticides take longer to get registered in these states. Because pesticide labels are regulated by the federal government, there are several attributes of a product that must be listed on the label. Thanks to this, deciphering pesticide options becomes much easier.


One of the most helpful bits of information on a label, from a purchasing standpoint, is the active ingredient, or the substance that does the killing. This is usually found towards the bottom of the front colored label on the bottle. The active ingredient is listed as a percentage, which allows you to compare products based on the amount of product in the bottle.

For example, a bottle of concentrate may have 80% of the active ingredient, but a bottle of ready-to-use product in a spray bottle may have only 2.5%. It is common for different companies to sell the same active ingredients under different names.

This active ingredients section allows you to compare different brands. It’s also helpful to look at the other ingredients in the bottle, which may contribute to the efficacy of the product, but not actually kill the target. For example, some products include water conditioners and other compounds that increase coverage on plants.

The front of the bottle will also have helpful information like the trade name, or the name assigned by the company for marketing purposes. This is done so you do not have to remember you used glyphosate to kill your weeds last time—the name Round-Up may pop back into your mind a bit faster. You can also find the EPA registration number showing the EPA has approved the product for sale, and another important thing to look for is the signal word.

This is a single word you can pick out that is prominently displayed, allowing you to determine how hazardous the product is. The signal words are Caution, Warning and Danger/Poison, in order of increasing hazard, so you know instantly if you are dealing with a product that could be hazardous to your health.

Safety Considerations When Using Pesticides

When using pesticides, always read the entire label before opening the container. Many people only look for the directions on how much to use, but the label also has important information that goes beyond this, such as what to do if you spill some on your skin, what safety gear you need to wear when you are spraying it, and what pests it kills. It cannot be emphasized enough how important following the label is when applying pesticides, not only for your safety, but also for the efficacy of the product.

More is not always better. Application rates are written based on tests the manufacturer performs to maximize efficacy. Some insecticide and fungicide products may harm the plant if concentrations are too high.

For example, horticultural oil is a common product for controlling insects and plant pathogens, but if you spray too much, you can actually suffocate the leaves of the plant. This is a great example because horticultural oil is also used as a dormant spray on fruit trees and rose plants when there are no leaves. This allows it to be used at a higher rate. If you do not read the entire label and only pull the dormant spray rate, you can defoliate your plants.

Pesticides are a controversial topic in many circles and even organically registered products require proper handling and application. It is important to remember that the reason you are applying pesticides is to kill another organism and this is inherently hazardous.

Even products marketed as safe, such as pepper or garlic oil, can be eye and lung irritants. If you are interested in learning more, the National Pesticide Information Center’s website is a great resource.


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Written by Danny Klittich

Profile Picture of Danny Klittich
Danny Klittich M.S. is a doctoral candidate in entomology at the University of California, Davis and a research consultant with CleanGrow. His research focuses on increasing plant resistance and tolerance to arthropod pests. Other interests include biological control, integrated pest management and woodworking.

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