Floods, droughts, pests, oh my!

Listen to this story
Aphids on soybean plant.
About the author
Reporter, Iowa Public Radio
Kathleen Masterson was a Harvest reporter, based in Ames, Iowa, from 2010 to spring 2012.

When people hear the words "climate change" they generally think: the planet's getting hotter.  And while that's the big picture, the effects of climate change will be far more complex and far-reaching – and will likely vary drastically from region to region. 

Farmers in parts of Africa are experiencing extreme, debilitating droughts, and regions such as Bangladesh are facing flooding and sea levels rising as much as three feet.

In the Midwest, though, farmers are seeing warmer springs and more humid summers—and so far, on balance, that's been good for agriculture.

“Plant breeders have attributed at least one bushel per acre per year yield increases to better, more favorable climate,” said Gene Takle, a climatologist at Iowa State University.

Many of these weather changes that have boosted yields were predicted by NASA climate models in the 1990s, Takle said.

“The model showed that both winters and summers would have higher temperatures, winter temperatures would increase faster than summer temperatures, and that has occurred,” he said. “Nighttime temperatures would increase faster than daytime temperatures, and that also has been manifest. “

The result has been a longer growing season and more soil moisture.

But researchers say the changes also could bring more extreme —and unpredictable – weather such as more intense rainstorms, especially in the spring.

And that could spell trouble for farmers, said Iowa State University soil scientist Matt Helmers. More frequent pounding rains could wash away precious soil and fertilizer that the crops need to grow.

“During the spring of the year, there’s not much crop canopy and soils can be susceptible,” he said.

Stripped down

One of the likely consequences of climate change in the Midwest is more frequent, intense rainstorms, particularly in the spring — a time that's already ripe for soil erosion.
That's one of the reasons Iowa State University researchers are experimenting with how to reduce soil loss. At the Neal Smith Wildlife Refuge in central Iowa, they've set up small 1-acre plots of corn and soybean rotations on the undulating hills. Then they planted strips of prairie grass in parts of the fields to see if the long roots that remain in the ground year-round help hold soil in place.

Many farmers till crops under in the fall, and this churns up the soil, leaving it exposed, without roots to hold it in place all winter.  

 But there’s more.  In the last 30 years, moisture in the air in Iowa and the region has increased by 13 percent, Takle said.  

With more humid nights: “It means that we have dew on crops longer; it comes earlier in the evening, and it lasts longer in morning, so that's more favorable conditions for pests and pathogens, molds, fungus, toxins and so on.”

Gray leaf spot, white mold, sudden death syndrome, mycotoxin infestations, crazy top, common smut, stem rust, soybean mosaic virus ... Those are just a few of the crop diseases that have surged northward with warmer, wetter weather in the Midwest, according to report by NASA scientists.

And Iowa State entomologist Matt O'Neal said warm weather currents also could serve to transport the insects more effectively because of the way many insects find food and homes – by flying straight up. 

“And then they get sucked into weather patterns... currents that pull them up into the atmosphere, get them into the jet stream, and then use that to get them far, far away, and then they literally get rained out of sky,” O’Neal said.

Higher temperatures also allow some insects to overwinter and emerge earlier, when young plants are still vulnerable.

O'Neal is studying aphids. Infestations of these pen-point sized critters can literally suck the life out of crop plants.

“They're also flying dirty hypodermic needles, with their piercing sucking mouth parts, as they move from plant to plant, their mouth parts are these sort of dirty needles that might pick up a little virus from infected plant, and then travel to another plant and spread it,” he said.

It doesn't sound good.  But O'Neal said there are things farmers can do to limit pests and pathogens. He's working with scientists breeding aphid-resistant soybeans, and a plant pathologist who's trying to develop a sort of natural vaccine that could make plants resistant to the viruses.

“Farmers adapt to everything: new pests, markets, rising prices. They have just over years learned to adapt,” Takle said. “Climate change is nothing new for them."