Climate Impacts on the Farm

There is a long list of things farmers keep an eye on. Top of the list: the weather. Because weather touches everything from pest management to planting. 

“The weather is something I look at three or four times a day, especially during the growing season,” said Neal Bredehoeft, soy checkoff farmer-leader from Alma, Missouri. “And that’s something I’m sure is true for every farmer —continually watching the weather.”

Researchers are also watching the weather. Changing weather patterns over time point to one big idea: the climate, or weather patterns we have grown to expect, is changing. 

“We’ve already felt some impacts of unprecedented rainfall rates,” said Andy VanLoocke, professor of agronomy at Iowa State University. “You don’t have to be an expert to see the impact intense weather has had on the ability to get things done in the field.” 

In the early 2000s, VanLoocke said it might not have been clear that precipitation rates were changing, but now it’s apparent. 

“Climate is a gradual phenomenon by definition and nature. But with each of the last few decades, it’s become increasingly clear that there’s been a shift in weather patterns,” he said.

Climate Impacts Pests 

Increased nighttime temperatures and higher humidity levels are also impacts of climate change. Those changes have an effect on pest patterns, said VanLoocke.

Daren Mueller, an associate professor, extension plant pathologist and coordinator of the ISU Integrated Pest Management Program at Iowa State University, agrees. He said frogeye leaf spot and Cercospora leaf blight used to be Southern region diseases. 

“We have some diseases we’ve traditionally thought of as Southern or mid-South diseases, and we’re starting to see those consistently further and further north,” said Mueller. 

Cercospora leaf blight is caused by the fungus Cercospora kikuchii and favors warm, wet weather, according to the Crop Protection Network. Foliar symptoms usually are seen at the beginning of seed set and occur in the uppermost canopy on leaves exposed to the sun. Leaves are typically only discolored on the upper surface, with symptoms ranging from light purple, pinpoint spots to larger, irregularly shaped patches. Affected leaves may become leathery and dark purple with bronze highlights. Symptoms may be confused with sunburn, which typically occurs on the leaf’s underside.

According to the Crop Protection Network, frogeye leaf spot of soybean is caused by the fungus Cercospora sojina. The disease occurs across the U.S. and in Ontario, Canada. It initially appears on upper leaf surfaces as small, dark, water-soaked spots. Eventually, these lesions enlarge and become round to angular, then the centers of frogeye leaf spot lesions progress from gray to brown to light tan and are surrounded by a narrow reddish-purple margin. On some soybean varieties, you may also see a light green halo around the lesion border. 

Changes on the Farm

Although flooded and swampy fields speckled the soybean growing region in recent years, Bredehoeft said increased rainfall has seemed to come at opportune times on his century-old family farm in Alma, Missouri.

“Our soil dries out pretty rapidly if we don’t get sufficient rain,” he said. “Over time, we’ve gotten rain that has been timelier for the crops, so overall I think the change has been more positive in my location.”

With increasing rainfall, Bredehoeft added he has taken extra steps to decrease erosion, such as implementing cover crops and no-till practices. 

“We’ve changed our operation a lot over the time I’ve farmed,” said Bredehoeft. “We went from heavy tillage to no-till and planting cover crops. We’ve made a lot of changes to reduce soil erosion and keep the nutrients on the field.”

Facing Whatever Comes

“The thing with diseases is, it doesn’t matter how the conditions are —something is always worse,” said Mueller. “It doesn’t matter if it’s a hot, dry year or a cold, wet year. The stars will align for one pathogen.”

Bredehoeft said he had experience with frogeye leaf spot about three years ago but nipped it in the bud by changing soybean varieties. 

Each field is like a fingerprint, with its own history, strengths and weaknesses. Being ready for changes in seed treatments, seed varieties and management practices to suit each fingerprint is key to not only success, but to stay ahead of changes and combat potential new resistance.

“We in agriculture adjust. We don’t do the same thing we did 30 or 40 years ago,” he said. “We adjust our operations accordingly because we do have to pay close attention to the weather and the climate. We as farmers have to have the ability to adjust according to conditions.”

Trent Ford, Illinois state climatologist, said climate models show increasing temperature and an increase in total annual precipitation throughout all seasons. All is expected to continue.

“The kind of trends that we’ve seen over the last 30 to 50 years, especially related to excess water, is something that is likely to continue,” said Ford. “Developing strategies for dealing with excess water issues and more water quantity variability, like having a lot of water in the springtime and possibly having some water shortages in the summertime, is something that would probably be beneficial as we continue to see these changes in our climate.”

Regardless of your climate, scouting is a critical practice for combatting pests. When scouting, it’s crucial you don’t use applications at the first sign of disease. Instead, keep an eye on the problem and wait until the pest reaches an economic threshold, which is different for every farm and field. 

Rapid resistance development among weeds has been documented. For many diseases, there are relatively few sites of action to choose from. In preparation to face whatever comes, farmers must diligently protect the management tools currently available.

Take Action, a stewardship initiative from the soy checkoff, has resources to help farmers adapt to changing climates and reduce the chance of fungicide resistance. Visit IWillTakeAction.com or download the app on the App Store or Google Play.