Effects on biota

Plants
Nitrogen fixation, which is required for the growth of higher plants, is hindered by pesticides in soil.The insecticides DDT, methyl parathion, and especially pentachlorophenol have been shown to interfere with legume-rhizobium chemical signaling.Reduction of this symbiotic chemical signaling results in reduced nitrogen fixation and thus reduced crop yields.Root nodule formation in these plants saves the world economy $10 billion in synthetic nitrogen fertilizer every year.
Pesticides can kill bees and are strongly implicated in pollinator decline, the loss of species that pollinate plants, including through the mechanism of Colony Collapse Disorder,in which worker bees from a beehive or Western honey bee colony abruptly disappear. Application of pesticides to crops that are in bloom can kill honeybees,which act as pollinators. The USDA and USFWS estimate that US farmers lose at least $200 million a year from reduced crop pollination because pesticides applied to fields eliminate about a fifth of honeybee colonies in the US and harm an additional 15%.