Stinkbugs reported in Arkansas: Southwestern corn borers in Delta

Southwestern corn borers are invading Mississippi corn fields, said Extension specialist Erick Larson. There's not a crisis situation yet, “but we are seeing an increasing number of the borers in our pheromone traps. Some fields are approaching threshold levels.”

In the past, Southwestern corn borers have been limited mostly to the Delta areas and bordering bluff counties in the state, said Larson. But in June, farmers saw a late infestation of first-generation borers in the extreme northeastern part of the state in Alcorn County.

The problem with corn borers is they have only a short time period when they're susceptible to sprays. Once they burrow into plant tissue, it's a coverage problem for insecticides.

Mississippi has received a Section 18 exemption for the use of Intrepid on Southwestern corn borers. “We didn't get the exemption because of a terrible outbreak. Intrepid may allow us better control, though. Intrepid may offer better residual activity so farmers can catch more of the young larvae when they hatch from egg masses,” said Larson.

The second generation numbers for borers are picking up. “I want to offer a warning that with northeast fields showing significant numbers, the consultants and farmers need to be aware of the situation.”

For each Southwestern corn borer per stalk, a plant is probably losing between 6 and 8 percent yield. The plant could also sustain stalk damage that results in lodging or ears dropping prior to harvest.

“So not only could a farmer lose that percentage of his grain weight, there's also a risk of additional losses. It can be a devastating pest,” said Larson.

Meanwhile in Arkansas, stink bugs are showing up in corn fields.

“We're getting a lot of calls on stinkbugs in the corn. No one knows quite what to do with them,” said Arkansas Extension specialist William Johnson.

The state already has some “stunted-up” corn from early feeding activity when corn was knee-high to waist-high. But now stinkbugs are piercing the ears.

“Most people think this won't be a huge problem. But one of our entomologists has some chemical trials out to see if something will work — just in case,” said Johnson.

Larson got a call from a grower in the Clarksdale, Miss., area who has stinkbugs were in his corn.

“Generally, once corn reaches tasselling and silking stages, its susceptibility to stinkbugs decreases considerably. There have to be numerous stinkbugs per plant to cause much damage.

“However, they can cause a lot of damage if they're in a corn field two or three weeks before silking,” said Larson.

Stinkbugs will actually pierce a plant and inject a toxin into developing ears. That leads to a deformed ear, often termed a cow horn effect. The affected ears are generally 6 to 8 inches long and curved.

In general, the corn crop across Mississippi looks very good. “I'd still like to see rain on the dryland crop for the next couple of weeks. Most of our crop should reach maturity beginning the last week of July. So there's still some time we'll need some moisture on the corn crop,” said Larson.

Johnson is even more enthusiastic about Arkansas' prospects. “From what we're seeing, this could be a banner year. The state had been needing some nice rains on our crop. We got those rains in most places and some cooler weather, too. As a result, farmers are saying this is the best corn crop they've seen.”

Just from pulling ears, it appears that Arkansas has an abundance of 175 to 220 bushel corn, Johnson said. The Arkansas River valley area (which, for the most part, isn't irrigated) should have 150- to 170-bushel corn.

“I think this will be a record crop. Our current record is 132 bushels or close to that. Not having to irrigate all hours every day, this has been a great corn growing year,” said Johnson.

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