The ecological, economic and agronomic disaster accompanying herbicide-tolerant transgenic crops is by now well known: over 10 million acres of superweeds resistant to Monsanto's weedkiller, RoundUp; farm machinery breaking on RoundUp-resistant pigweed thick as a baseball bat; Monsanto paying farmers to spray their fields with competitors' herbicides; a new generation of transgenic crops in the pipeline engineered to withstand older even more dangerous chemicals like 2,4-D.
Last week brought more bad news for Monsanto: the same phenomenon is also occurring in insect pest populations that are developing resistance to transgenic "Bt corn" in the Midwest.The Wall Street Journal recently reported Iowa State University's findings that the corn rootworm is for the first time proving resistant to the insecticidal toxin, Bt, in transgenic corn in Iowa. Four days later, Business Week reported Bt corn plants in northwestern Illinois toppling over after root damage caused by the same insect, apparently as impervious as its Iowa cousins to the engineered Bt toxin. Likewise, insect resistance to transgenic Bt crops in India (where dramatic crop failures resulted) and South Africa has been reported.
This is a classic case of the pesticide treadmill. A pesticide application (whether sprayed the old-fashioned way or applied through a crop plant engineered to contain that toxin in its cells) typically kills many - but not all - of the targeted pests. Of those that survive, some will pass on their genetic traits of pesticide resistance to their offspring, gradually leading to a more and more resistant population. Farmers get trapped on this treadmill as they are forced to use more - and increasingly toxic - chemicals to control pest populations that continue to develop resistance to each new type or class of pesticides.