Agricultural chemicals are wiping out bees that pollinate our crops and flowers.

RODALE NEWS, EMMAUS, PA—Bee fan or not, we all rely on the insects to pollinate the fruit, nut, and vegetable crops we enjoy every day. But in the last few years, the populations of our pollinators, particularly honeybees, have been plummeting. Dubbed colony collapse disorder, the cause of the devastation isn't known. There are many theories, from mites and viruses to cellphone towers. One potential cause—pesticides—gained more credibility this week with the release of a new study by Pennsylvania State University. Researchers found "unprecedented levels" of pesticides in honeybees and hives in the United States.

THE DETAILS: Scientists tested wax, trapped pollen, and honeybee specimens for chemical pesticides and chemicals originating from those pesticides. Investigating pesticide residue in samples taken from beekeepers from 23 states and one Canadian province during the 2007 to 2008 growing season, researchers found 121 different pesticides and metabolites in the 887 wax, pollen, bee, and hive samples. Nearly 60 percent of the 259 wax and 350 pollen samples contained at least one systemic pesticide—a type of poison that doesn't remain on the surface of plants, but is taken up inside the plant, too, where honeybees go to feed. Here are just a few of the chemicals they uncovered:

• Coumaphos—An insecticide used to control livestock pests, such as flies, lice, scabies, and ticks. It interferes with proper functioning of the nervous system of both humans and insects and is also highly toxic to birds. This type of pesticide falls into the organophosphates category, a class of pesticides that has been linked to the most common type of childhood cancer.

• Carbaryl—A wide-spectrum insecticide designed to kill insects on citrus, other fruit, and cotton, and on trees and in lawns.

Read on to find out other harmful chemicals that have been found in hives.