A Conversation with an Herbicide Expert

Featuring Sara Allen: Crop Protection Engagement Manager

What are herbicides and how do farmers use them? What other tools and processes do farmers use to protect crops? Are herbicides safe? Let’s talk about herbicides and their role in modern farming.

Herbicides are a crucial tool to help farmers safely and effectively manage weeds, which rob farmers’ crops of vital nutrients and water. Herbicides help farmers grow food as efficiently as possible while conserving natural resources, like water and land.

Q: What is an herbicide?

A: An herbicide, also commonly known as a weed-killer, is a chemical that protects crops from weeds.This is important because weeds can steal water and nutrients from plants that farmers are trying to grow.

Left: Soybean field with weed, disease, and bug injury. Right: Clean field.

Q: What is the difference between herbicides and pesticides?

A: Pesticide is a general term for tools that farmers can use in a very targeted way to protect their crops from weeds, insects, and diseases that can ruin a harvest. There are three main types of pesticides: herbicides, which protect plants from weeds that can steal water and nutrients; insecticides, which protect plants against harmful insects; and fungicides, which protect plants from fungi that spread disease.


Can you tell me why pesticides are such an important tool?


Every year, nearly 40 percent of the world’s potential harvests are lost to weeds, insects and disease. These losses could double without pesticides and other crop protection practices. Most farmers, including conventional and organic farmers, use some type of pesticide to protect their crops.

Q: How are herbicides used?

A: Herbicides are most effective when used in the right place, at the right time, and in the right amount. Farmers use them in combination with a variety of other tools and products. Technologies like GPS, variable rate sprayers and data analytics help farmers apply only the necessary amount of herbicide.

Q: How do we know herbicides can be used safely?

A: Like all pesticides, herbicides undergo comprehensive evaluations from regulatory authorities, including the Environmental Protection Agency (EPA). In the U.S., more than 100 safety studies are conducted before a product becomes available to farmers. Once an herbicide is approved, it is routinely reviewed by regulators to make sure it can continue to be used safely based on new information, and no regulatory approval is permanent.

In many states, farmers are even required to receive regular training and certification in proper use of herbicides. State Pesticide Education Programs provide information about safe and effective use of these products.


How much herbicide do farmers use?


It’s important to understand just how small the amount of pesticides involved in growing food is. The amount of active ingredient that goes on one acre of crops (a space large enough to hold about 240 cars) is roughly 12 fluid ounces, or the size of a can of soda. That’s because modern herbicides are very effective and targeted tools. Discussions around “dousing” crops with chemicals are misleading.

Q: How often are farmers thinking about controlling weeds?

A: Daily! During the off season, they’re trying to figure out what they need to buy and what they can buy ahead of time at the best price. During the season, they’re constantly looking at the weather, predicting challenges, scouting their crop, determining how to time applications. It’s a fine balance between wanting maximum effectiveness and timing things with nature.

When it comes to their livelihood, farmers live it, eat it, and breathe it. When they put a seed in the ground, at that time it has its greatest yield potential. Every day after that, it is threatened by weeds, rain, weather, diseases, animals and insects. To protect their bottom line, farmers want to control pests by using the right product in the right amount at the right time. Farmers only want to apply as much pesticide as needed to control the issue.


In addition to using herbicides, how else do farmers fight weeds?


Crop rotation, tillage, seed selection, scouting fields for signs of weeds, pests and disease, hand-weeding, cover crops and even adjusting the spacing between rows during planting are effective weed management tools.

Q: That’s interesting about row spacing. How does the spacing between rows help fight weeds?

A: The faster a crop reaches canopy—the point at which plants from consecutive rows nearly touch each other—the better it can suppress weeds. That’s because the shade cast by the canopy prevents sunlight from reaching weed seedlings, preventing robust growth of the weeds. When plants can protect themselves from weeds, farmers let nature take its course.

Continuing the Search for Efficiency

Herbicides are an important tool that help farmers have better harvests while using resources more efficiently. Using only what’s necessary, whether it’s water or the herbicide itself, is good for farmers’ crops and their bottom line. Crop protection scientists truly value open and transparent discussions. The most important thing to remember is that herbicides are just one tool in the crop protection toolbox.