Can a new wasp help protect soybeans?

Asian wasp
To understand the Asian wasp experiment, it's important to understand the insect's lifecycle. George Heimpel, an entomologist at the University of Minnesota, says it's sort of like the movie "Alien." The wasps lay their eggs inside the soybean aphid and the aphid hatches and turns into larvae and that larvae feeds on the aphid from the inside out.
Photo courtesy Dr. Roy Scott

Asian wasps aren't very scary. They're only about the size of a speck of dust. They don't sting and they really can't fly far. Their only purpose is to eat the soybean aphid.

Researchers say to understand their project, it's important to understand the lifecycle of the Asian wasp. George Heimpel is an entomologist at the University of Minnesota.

"They lay their eggs inside the aphid and the aphid hatches and turns into larvae and that larvae feeds on the aphid from the inside out. So it's kind of like the movie "Alien," Heimpel says.

Aphids on plant
Soybean aphids on a plant in the South Dakota State University research greenhouse.
MPR Photo/Cara Hetland

Except in this horror scene, the aphid kind of dries up and the adult wasp emerges. Then, the cycle starts over again.

To the naked eye the soybean aphid is a tiny yellow dot. There are usually hundreds on a single plant. Their damage costs farmers millions of dollars nationwide.

The soybean aphid feeds by sucking the soybean plant dry; they can destroy as many has half the plants in a field. Because the aphid came from China, researcher George Heimpel went to the aphid's homeland to find its natural predator.

The last five years he's worked to get federal approval to release the wasps. The release of bio-control agents or insects is strictly regulated. There were tests to ensure the wasps won't eat anything else. Heimpel says there've been releases in seven midwestern states.

"The purpose of the first year is to see whether they'll reproduce in the field soybean fields and we're now showing that they will and the second goal is to determine if they'll over winter," Heimpel says.

Field cages
Field cages in the test plot keep Asian beetles and other insects out.
MPR Photo/Cara Hetland

The climate in China is similar to the extreme Midwest temperatures in summer and winter. Heimpel is almost certain the wasps will survive.

This experiment begins in a very controlled setting; a greenhouse. In a greenhouse at South Dakota State University, fans rumble in the background keeping the temperature constant. The soybeans here are covered in aphids. A few of the potted plants are in small white tents called bug dorms. In these dorms, the Asian wasps are reproducing by inserting their eggs in the aphid. Once there are hundreds of wasps ready to hatch, the next step is to release them in a soybean field.

On the edge of the South Dakota State University campus are research test plots. In the small area designated for soybeans there are three mesh tents called field cages. Inside are the potted plants from the greenhouse. The goal is to get the wasps to hatch and spread to other plants in the cage.

Kelley Tilmon, research entomologist at South Dakota State University is in charge of releasing the wasps in South Dakota.

Tilmon has removed one of the cages. The wasps didn't reproduce the way she had hoped. That's because another insect was already on the plants in the cage.

Kelley Tilmon
South Dakota State University research entomologist Kelley Tilmon.
MPR Photo/Cara Hetland

Tilmon is hoping for a better success rate in the other field cages. She says it could take several years before the wasps spread. That's one of the reasons the release is happening in several states at once.

"It's kind of a long term project. These things depend on population cycles of insects and migration patterns and they don't necessarily happen quickly," Tilmon says. "So, it is a long term investment that potentially has a long term pay off in the future. Because once they're established, they work for free."

The project is funded mostly by the North Central Soybean Research and Promotion Council. So far, the farmer-supported group has contributed about $2.5 million. Spokesman David Wright says this is the first time farmers are investing in a natural way to control a pest.

"It was time to think outside the box, it was a new species of aphid and one they knew could be controlled because the soybean aphid in it's homeland of China is not a problem," Wright says.

By next year, Wright says, farmers will be lining up to use their soybean fields to release the Asian wasps. He says as they get the soybean aphid under control, he's certain researchers will have a new pest or disease that will make its way to the Midwestern crops.

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