An insect infestation can trigger panic in anyone—especially when a serious pest threatens your home or garden. And while we might be tempted to reach for anything that promises to stop whatever is causing the destruction, it’s worth hitting “pause” on this impulse to dig a little deeper. When it comes to pesticides, the promise of a quick fix often comes with unintended consequences. In some cases, the chemistry of the product is more harmful than the intended pest.

Don’t be fooled—pesticide chemistry is serious business. Even “eco,” “organic,” or “natural” pesticides need due diligence to ensure the product you choose won’t have harmful side effects on your health or your environment. The number one rule when considering or choosing pesticides is to read the label.

The law requires pesticide labels to provide information about safe use, storage and traceability. To determine which pesticides are the most effective and the least toxic to apply, it’s worth carefully reviewing a few areas on the label prior to bringing a pesticide home.

Signal Words

The words “danger,” “warning,” and “caution” are likely familiar to anyone who uses basic household cleaning products. These words are the first indicator of how toxic a product will be to humans and animals. If there are two products that control the same pest, signal words can help you choose which one is the least toxic. Here are standard terms ranked in order of the most toxic to the least toxic.

Danger PoisonHighly toxic by any route into the body.
DangerCan cause severe eye damage or skin irritation.
WARNINGModerately toxic either orally, dermal, or through inhalation; causes moderate eye or skin irritation.
CAUTIONSlightly toxic either orally, dermal, or through inhalation; causes slight eye or skin irritation.

Active ingredients

As a horticulturalist, the first thing I look for when I pick up a bottle of any chemical compound at a store are the “active ingredients.” What exactly am I putting around my home? You might want a product to get rid of ants, but what’s the active ingredient that’s going to do the work?

By law in Canada and the US, the formulation of the pesticide must be on the face of every pesticide container, listed as “Active Ingredients” or “Guarantee.” Each active ingredient is identified by its common name. The concentration is listed as the percentage by weight or volume.

While these names may not be part of your regular vocabulary, a quick search on your smart phone will help you find the LD50 rating and details of any health concerns. You can do a pesticide label search on your mobile device. Health Canada offers online searching or searching via apps. In the US, you can search online through the Environmental Protection Agency (EPA) or at

An LD50 rating is the measure of the lethal dose and concentration of a toxin, radiation, or pathogen. The value of LD50 for a substance is the dose required to kill 50% of the members of a test population over a duration of time. These figures are commonly used as indicators of a substance’s acute toxicity. The lower the LD rating, the more toxic the substance, no matter what it’s source.

You can also look up the Material Safety Data Sheet online for any product used to deter pests. The MSDS (often called the ‘safety data sheet’) provides the most detail about a product.

The Fine Print: Reading Pesticide Directions

More is not always better, especially with pesticides. The directions on a pesticide label describe the most effective application method, timing, and quantity to apply. These instructions tell you the exact amount needed to kill the intended pest with the least toxicity to the surrounding environment. Not only is it your responsibility by law to follow the instructions, it is also the most effective and cost efficient.

What to look for:

  • Is this product intended for the pest you are looking to manage?
  • Is this product the least toxic option for managing that pest?
  • Are there other physical or biological controls you can take to manage the pest instead?
  • If you do choose to use the product, can you carry out the instructions as prescribed?
  • How long after treatment can vegetables be eaten or an area re-entered safely?

Storage and Disposal

After you use a product, how will you store the remainder or dispose of it? Whether “natural” or “conventional,” these products are not safe under the sink or in the closet. They need to be stored in a secured space at the temperatures detailed on the bottle. To find out where to dispose of your unwanted pesticides, contact your local waste management centre for your municipalities hazard waste depot.

Protective Wear

While preparing this article, I polled a number of friends and family about their own use of pesticides. Unfortunately I found myself giving a few lectures when I learned most of them did not follow label instructions or don any protective wear for application. Even the smallest amount of a chemical on your skin, in your eyes, or inhaled into your lungs can cause serious health implications. It’s essential to wear gloves, safety goggles, and a respirator if you are ever using chemicals.

Poisoning Indicators

We’ve all heard stories of a person chopping chillies only to rub their eyes! The same unintended contact issues exist for pesticides. Even small amounts can trigger symptoms such as headaches, fatigue, dizziness, restlessness, perspiration, nausea, diarrhea, loss of appetite or weight, and more.

If you are suffering from any of these symptoms and suspect pesticide poisoning, seek medical attention immediately and bring the pesticide along. And don’t forget that your pets could also come into contact with these substances and suffer the same ill effects. Keep them indoors during application and take precautions to prevent them from encountering these substances when they go outdoors.

A word about homemade pesticides like rhubarb or tobacco…

There are a thousand homemade pest control remedies to be found on the internet, very few of which have actually been tested for efficacy or safety. Just because you are creating something from ingredients found around the home does not make it safe. A common home remedy that I’ve seen promoted is boiling parts of the rhubarb, tobacco, or chrysanthemum plant and using the water as a pest treatment. WARNING! Solutions made from these common plants have serious health risks and can even lead to death.

A Final Word

The overall recommendation for pesticides is to use them as a last resort after first trying physical, cultural, and biological controls. Though agriculturalists and some gardeners use pesticides on a schedule, this is especially destructive to beneficial insects and other organisms. If repeated applications are necessary, the pesticide is merely a band-aid solution.

Remember: treat chemicals of any sort with caution and use chemical pesticides only as a measure of last resort. Reading the label and educating yourself leads to well informed choices and ultimately a healthier garden and home.

Ed. Note: We’ve never needed to use chemical pest treatments in our vegetable garden. Using organic methods when gardening builds healthy soil, which produces healthy plants. A vigorous plant is more resistant to pests or disease.

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