By Rhett Butler   |  Last updated July 22, 2007

Plants have been synthesizing chemicals for millions of years to protect them from predation by insects and infection from disease. Thus rainforest plants have developed a complete array of natural pesticides. These pesticides can be isolated, and some can be synthesized in the laboratory by pharmaceutical companies. These natural pesticides are effective for protecting cultivated crops from destruction by pests and disease, without the adverse effects of chemical pesticides like DDT.

New research shows that using natural predators like wasps and flies combined with limited use of pesticides is more effective in eradicating pests in the tropics than regular spraying with synthetic pesticides. Chinese scientists have even engineered wasps to deliver lethal viruses to insect pests.

In addition to protecting crops from infestation, many rainforest plants can be used as insect repellents. The roots of the liana, a philodendron from American rainforests, have an odor that keeps away mosquitoes, while the bright orange berries of another New World plant, Bixa orellana, are effective in deterring biting insects, in addition to being used as a body paint and dye. These compounds may be further studied and analyzed by pharmaceutical companies to create new insect repellents that might be less detrimental to the skin and plastic materials than conventionally-used DEET. These highly effective insect repellents are more ecologically sound and inexpensive to produce.

White fungi in Peru's Manu National Park
White fungi in Peru's Manu National Park. (Photo by R. Butler)

Review questions:

  • Why are plants a good potential source for natural pesticides?

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