Climate Change Will Challenge Farmers as Crop Pests Spread

The Midwest's cold winters play an important role for farmers: They prevent devastating crop pests such as corn earworms and corn borers from becoming established in their fields. Corn earworm pupae, for example, can't survive more than about five days at temperatures below 14 degrees Fahrenheit.

As global warming continues, however, the range of crop pests and their ability to survive the winter increases.

"Increases in temperatures, even summer temperatures, generally benefit these pests. An effectively longer season, or more days exceeding their minimum temperature range, provides them with additional time to feed, mate and reproduce," said Purdue University entomologist Christian Krupke, who studies the impact of climate change on crops pests.

The corn earworm is just one clear threat. It's already established in the South and has resistance to many of the current pesticides, making it tough to manage.

Scientists expect climate change will similarly impact many types of crop production across the U.S. in the next several decades as deadly crop pests and fungi flourish in the warmer and, in some areas, wetter weather.

As warming increases, three issues affect U.S. crops in terms of pests:

*survival thresholds rise, leading to overwintering and more generations every year;

*ranges push northward, leading to new kinds of pests in areas that haven’t formerly had to deal with them; and

*increasing use of pesticides to offset the first two effects, leading to increasing tolerance of existing pesticides, will further exacerbate the pest problem.

A U.S. Global Change Research Program report (which was withheld by the Bush administration) projected that climate change would cause an increased use of pesticides over the next 80 years on corn by 10 to 20 percent, on potatoes by 5 to 15 percent, on soybeans by 2 to 5 percent, and on wheat by an unknown quantity.

Another potentially deadly impact on wheat was discovered in Uganda in 1999: the wheat stem rust Ug99. It is described as a "time bomb" for world wheat production and has already spread to Iran. Scientists are working on hybrid strains of wheat that show resistance to Ug99.

If the fungus makes its way around the globe, it represents a significant threat to global food security, says Rick Ward, a wheat geneticists at Cornell University. Wheat is the staple food of billions, matched only by rice in Asia.

For U.S. food in general, the impacts of climate change and hardier pests might be as straightforward as higher food prices, as farmers resort to more insecticides to keep crops from being ravaged and spend more in labor costs for “spotters” to identify pests in their fields. Or the effects might become as complicated and devastating as the food shortages currently being experienced in some third world countries. It all depends on how timely and comprehensive U.S. policy is in dealing with greenhouse gas emissions like carbon dioxide.

As David Wolfe, professor of plant ecology in Cornell University’s Department of Horticulture (and a leading authority on the effects of climate change and rising atmospheric carbon dioxide on plants, soils and ecosystems) asked in his recent op ed, how far are we willing to let it go?

His answer was more hopeful than one might expect: