Pesticides are substances intended to kill or repel insects, animals, plants, fungi or pathogens considered to be pests. Though people have used pest control methods for thousands of years, the 20th century was the first time mass-produced synthetic pesticides were used on an industrial scale.

Science has brought to light many concerning health, environmental and economic impacts of pesticides.

What are common categories of pesticides?

From common weed killers used on lawns to common household cockroach bait and ant spray to the more than 1,000 agricultural pesticides used in conventional farming, the term pesticides includes insecticides, herbicides, fungicides, rodenticides and other categories of substances that target specific pests.

How are pesticides applied?

Pesticides in liquid form can be sprayed via a tractor or hand-held device. Those in solid form may be spread as granules, dusted over the targeted area or applied as a seed coating. Some pesticides may be applied via cropdusters – small planes or helicopters that fly over crops.