Beneficial insects offer numerous advantages to producers
There is no crime in plagiarizing Mother Nature.
That is, in essence, what farmers are doing when they mimic nature and interseed cover crops into established cornfields to suppress weeds, impact pests and beneficial insect communities, said Michael Bredeson, a doctoral student with the Ecdysis Foundation and South Dakota State University.
Bredeson spoke at the 2018 Soil Health U about his research.
A study he helped conduct last year showed that cornfields with a diversity of insects have fewer problems with pests, such as corn earworm and aphids. There also are more bacterial and microbial activity in the soils and on the ground.
“Insects are doing incredible things out there,” he said. “They work for us in many respects. There are crickets out there eating weed seeds. There are ground beetles and all sorts of spiders—thousands of different species in our ecosystems that are performing wonderful tasks for us. They are consuming herbivores that are trying to take yields away from us.”
Designing a landscape of covers
Bredeson compared farmers to architects designing an elaborate building. The same must happen in their barren fields.
Bredeson said farmers design rotations and cover crop regimens to improve and benefit their operation.
“We need to think about designing our agriculture system so these workers (insects) can maximize the benefits they can offer us.”
And, like an architect, the design must withstand the elements. A poorly designed system will leak, create soil erosion and lack water infiltration.
“Mother Nature has been doing this longer than we have and is pretty successful at it,” he said.
For most conventional operators with a monoculture growing in their fields, Mother Nature wants to heal the barren wounds.
“The first thing Mother Nature wants to do is put a Band-Aid on that,” he said. “That is where the weeds come in. By using interseeded cover crops, you will fill that gap.”
A cover crop between the rows prevents weeds from coming up, and this helps cut back on chemical use, he said. At the same time, farmers will see benefits from the different cover crops they select to fill the gaps.
Interseeding not only covers the bare soil but also lowers the wind velocity on the ground. It allows for greater water infiltration by slowing the velocity of the water and making it follow the root channels underground. Meanwhile, covers help absorb excess nutrients, increase organic matter and raise the carbon content of the soil.
Just like humans, each plant has its own special makeup and different smell. It is how pests that eat corn know where to fly.
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He noted the corn earworm has a reduced eye structure but incredible antennas that allow them to smell the chemical composition in corn.
With interseeded cover crops, that pest might land on something green, take a bite and realize it isn’t corn.
This leads to a concept called the flypaper effect.
“If we have designed a system supported by interseeded cover crops, then it might get gobbled up by beneficial insects,” he said, adding, “We have an army already established rather than reacting to a pest outbreak when it is too late.”
Simply having predators around, even if they don’t consume a pest, also reduces the performance of that pest that wants to feed on the corn plant.
“There are multiple ways to stack the deck against these corn pests,” he said.
Study shows benefits of covers
Last summer, Bredeson helped conduct a study with two volunteer farmers. Each farmer had two plots of corn they interseeded with cover crops and two plots with barren ground. They planted a seven-way mix that included flax, field peas, lentils and hairy vetch.
Bredeson and a team collected insects on the plants, crawling on the ground and also deep in the soil.
There were more beneficial insects in the cover crop plots than the plots with no cover.
“We had almost a thousand more animal arthropods per square meter in interseeded cover crop plots versus no cover crop plots,” he said. “In every two square centimeters of soil there was an animal milling around eating dead plant matter, hunting. It is amazing how much life there is after one season.”
He said yields didn’t decline much between the interseeded and conventional acres. One farmer saw similar yields in both plots. The other saw a slight decrease in his cover crop acreage.
However, there are a multitude of benefits, he said. Biological control will replace chemical control, saving on input costs, he said. Soil health improves. Also, interseeding can help increase other species populations, including pheasants.
“When we use things like cover crop rotations, diverse crop mixtures and interseeded cover crops, we are designing a more resilient system,” he said. “It’s a system that supports a lot of beneficial insects, both those that consume pests and those that help our soil’s physical structure.”
Amy Bickel can be reached at [email protected].