For centuries, farmers – and their crops – were defenseless against diseases. Insect pests can ruin a crop in days. So can diseases like “rust” and “molds”. Weeds can outcompete crops and rob vital nutrients from the soil. They also shade sunlight, starving crops of sugars from photosynthesis. All these threats reduce yields, crop quality, and hurt profitability.

Whatever the culprit, agronomists have developed ways to help farmers fight back. Sometimes the answer is using better seeds. Farming practices like crop rotation help manage pests and diseases. Tighter row spacing can make crops more competitive with weeds.

But just like humans need antibiotics when we have strep throat, some crops need chemical help in the form of pesticides.

“Pesticide” is a very general, chemical term. There are several categories:

• Insecticides fight insect pests
• Herbicides fight weeds
• Bactericides fight bacterial illness
• Fungicides fight fungal illness

Each pesticide type is designed for a different target. When used properly, pesticides save time, fuel, and money. For example, it’s been estimated that if we quit using herbicides, everyone in the US would need to take a siesta from their regular jobs. The National Center for Food and Agricultural Policy calculates that to maintain today’s level of crop yields (to feed the world’s population), each American would need to do backbreaking weeding for one week straight¹. Most people probably don’t want to give up their vacation to join the “weeding corps”. And that’s really one dimensional – it doesn’t factor in diseases caused by fungi and bacteria, or insect pests nibbling away.

Despite this, pesticides get a bad rap. Why not just pluck off insects with our hands, remove diseased plants, or pull weeds? In a small garden plot, that’s not a problem. But on large farms, hand-removal is not a practical or affordable option.

There’s another problem if we stopped using pesticides. We’d have to use more land to produce the same amount of food. For example, if our yields are halved because of pests, it would require double the land to produce the same amount of crops. The problem is, land is in short supply. Either it’s too hilly and not suited for farming, or it’s already been paved over and developed as a city. And we can’t use areas like rainforests, because they’re an important part of Earth’s ecosystem.

When used properly, pesticides are also safe for human health and the environment. A farmer usually buys pesticides in 2.5 gallon jugs. You’d think s/he would go through that pretty quickly. Not always, because the use rates are really low. Sometimes ounces to the acre. Take Roundup, a very common herbicide. A farmer will add 22 fl. oz. of Roundup (roughly the same as a bottled drink) to a spray tank and add maybe 40 gallons of water. That Roundup is now really dilute – but it’s enough to take out 1 acre of weeds and not have any lingering effects on the environment or human health. One, because it breaks down quickly – and two, because there’s so little actual Roundup spread out over such a large area.

Then there’s Roundup Ready crops. A farmer can plant biotech corn, cotton, or soybeans that have the ability to breakdown Roundup – a chemical that would ordinarily kill the crop. But not in this case. The farmer can make a single spray pass over the field – scorching the weeds, sparing the crops, and minimizing soil erosion.

Whatever the delivery method, pesticides have a safe and effective track record when used properly. And pesticides are just one option in a pest management toolbox that farmers can rely on. If you’re using pesticides in your home garden, always read the directions! Farmers and agronomists are trained professionals. Your use impacts the environment, too.

So why pesticides? They’re chemicals used at low rates to treat pathogens, pests, or weeds. Antibiotics, and even your dog’s heartworm medication are pesticides! Plants get sick too. Anything that impacts crop health affects the affordability and nutrition of our food supply. Pesticides are an important tool to maintain crop yields, feed the world, and keep our food supply sustainable.

Answered by Timothy Durham, Ferrum College

1. Gianessi, L., and S. Sankula. 2003. The Value of Herbicides in US Crop Production. National Center for Food and Agriculture Policy. Available online

To read a story about robotic weeders being developed by agronomists, read here.

To watch a video about Weed Scientist Anita Dille, click here.

About us: This blog is sponsored and written by members of the American Society of Agronomy and Crop Science Society of America. Our members are researchers and trained, certified, professionals in the areas of growing our world’s food supply, while protecting our environment. We work at universities, government research facilities and private businesses across the United States and the world.