Gall midge

Soybean gall midge larvae in the pith of a white mold infected plant. Originally, it was assumed the midge accessed the plant via damaged areas.

Soybean producers can rest a bit easier now that light is being shed on eastern South Dakota’s newest pest.

The soybean gall midge discovered last year first in western Minnesota and then later in other parts of the tri-state area was believed to be two separate species. In addition, researchers initially thought that due to the extensive hail damage across the area, the midge was gaining access via that damage. After the research was conducted mainly in Nebraska and isolated places in Minnesota, Iowa and South Dakota, it has been determined that neither is true.

Dr. Ray Gane, a researcher with the USDA, determined that the midges found that looked different are actually one single new species of midge now named the Resseliella Maxima. Because of this, University of Minnesota Extension integrated pest specialist Bruce Potter believes the pest could be more widespread than initially believed.

“(We) don’t know how it was introduced,” he said. “It means it’s been around for a length of time.”

Because this single gall midge got into the plants in various ways, Potter believes he may have seen damage from this specific pest in the past but associated it with white mold instead of the pest.

“That damage made us made think it was a different species,” he said.

The good news for producers, if there is any in a new pest infesting your soybeans, is that Potter believes the gall midge actually comes up through the soil, not through damaged stems. Because of the extensive damage the infected fields had last year, it was impossible to tell. But now, knowing it is one pest getting in multiple ways, researchers believe soil tests will tell them how likely it will be to experience damage from the midge.

“There may be a way to tell what the risk for the following year,” Potter said.

The only thing that is for certain is that beans planted later in the season last year were less affected by the pest than those planted early. But even that, Potter warned, is circumstantial to that year.

The midge got the name "maxima" because the adults are relatively large when fully grown. In addition, the soybean scientific name also carries the word ‘max’ so it has a double meaning to clearly identify what plant the pest infests.

At this point in the season, Potter is unsure how the pest will infect this year’s crop, but as a researcher he is hoping it returns to help producers better understand how to predict, treat and deal with the midge.

“We may not see any problems this year,” Potter said. “That’s a little disheartening but it will be good if there isn’t another soybean problem.

“One of the joys of science is that you’re always learning and finding out a little bit more about biology,” he added.

Whether there is a problem or not, Potter said the extension office is ready. While sending out surveys around the tri-state area to see how far the pest has spread, his team will be on the ground in Minnesota to test fields directly. Luckily for them, the pest infests at the edges first so it should be easier to test.

Potter assumes readings will show the pest is well distributed throughout Minnesota and possibly into eastern South Dakota and northeastern Iowa.

“If people start to see this damage, please let us know and we can get a lot of that groundwork done,” he said. “The more we know about the distribution (the better). If a farmer isn’t seeing it, he could still have a problem later on from down the road.”

For now, Potter said it’s a waiting game. Researchers will be ready, and farmers should be preparing for another round of infestations, but if they don’t come, Potter said he won’t lose any sleep.

“I’d be just fine with never seeing them again. We have enough problems out there as it is,” he said.

Reach Reporter Jager Robinson at 605-335-7300, email or follow on Twitter @Jager_Robinson.