Managed Pollinator CAP Coordinated Agricultural Project A National Research and Extension Initiative to Reverse Pollinator Decline

摘要

In the last 10-15 years, the EPA has gradually eliminated many uses of several "older" classes of pesticides. These include the widely used organophosphates, a staple of many agricultural systems. This left farmers and chemical companies looking for alternatives. Anew class of pesticides called neonicotinoids, or neonics for short, were initially developed in the 1970's. The chemical structure of these is derived from nicotine (also an insecticide, keeps tobacco plants safe from caterpillars) and they are relatively non-toxic to most vertebrates. Most are water-soluble and break down slowly in the environment, so they can be taken up by the plant and provide protection from insects as the plant grows and develops. During the late 1990's this class of pesticides became widely used (primarily as imidaclo-prid, trade names include Gaucho, Provado, Merit). Beginning in the early 2000's, two other neonics began to see wide use to treat corn and other field crop seeds. These compounds are clothianidin (trade name Poncho) and thiamethoxam (trade name Cruiser), the latter rapidly breaks down into clothianidin in living organisms. Currently, virtually every corn seed that is planted in the Midwest is treated with one of these two compounds, along with a cocktail of fungicides. In addition, most soybean seeds are also treated with neonics (usually thiamethoxam). Clothianidin is one of the most toxic substances we know of for honey bees. The lethal oral dose to give a 50% chance of death (the LD50) among anexposed group of adult honey bees is about 3 nanograms per bee. That's 3 billionths of a gram, a tiny fraction of the weight of the bee (1/10 of a gram). Of course, toxicity by itself is not informative without exposure data. How often do honey bees encounter these pesticides? Where does this issue rank among the challenges facing honey bee health? These are