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Moth flights, stink bugs, 'Mohawk' corn

“Most cotton farmers have probably gone across at least part of their acreage treating for bollworms,” says Gus Lorenz, Arkansas Extension entomologist. “A lot of producers are currently spraying. We’ve got a serious moth flight going on right now.”

The flight appears to encompass the entire east half of the state. This is an unusual occurrence as flights normally begin in the south and move north, says Lorenz. In speaking with consultants from Mississippi County (in the northeast corner) all the way down to Desha County, “we’re typically looking at about five times threshold.”

The flight primarily consists of bollworms. But as focus moves to the northeast (Clay County and parts of Mississippi County), there’s a mix of tobacco budworms too. Producers there are treating conventional cotton with Tracer or Steward.

Also thrown into the mix in some fields: spider mites.

“We just came out with a new publication on spider mites. This pest is a pressing issue for some producers right now,” says Lorenz, who spoke at the July 24 Monsanto field day in Coy, Ark. “That throws a whole new twist into situations where bollworms are also in the field. Where you’ve got both pests in Bollgard cotton, Capture is probably a product of choice. In non-Bt cotton, Denim gives good suppression of spider mites.”

Regarding Monsanto’s new Bollgard II cotton, Lorenz and colleagues have evaluated it for the third year.

“We’ve been very impressed with its efficacy – particularly with the cotton bollworms and armyworms. It appears that Bollgard II will bring a lot more to the table than Bollgard.”

Pod delays

Stink bugs have shown up in the state’s cotton and soybeans. In cotton, the threshold for stink bugs is one per six row feet. For that reason, “stink bugs are tough insects to handle because with that kind of threshold they can be hard to find,” says Lorenz.

“With green stink bugs, pyrethroids work okay. In Bollgard cotton, some over-sprays should do a good job. If you’ve got brown stink bugs – and many fields hold browns – you’ll find they’re harder to kill. On browns, pyrethroids give about 50 percent efficacy so you might want to tank mix in some Bidrin or Orthene,” says Lorenz.

Speaking from the road where he’s touring fields, Byron McVay, Garst area agronomist for Missouri and Arkansas, says he’s also seeing stink bugs regularly. “At the end of the last couple of seasons, because of this pest, soybeans tended to stay green way past time for them to go ahead and mature. Also, there have been a lot of pod and seed damage from the stink bugs. This season, we want to get the word out early to make sure producers start watching for populations and get sprays out in time.”

McVay is seeing “a lot” more brown stink bugs this year. A typical scenario from Arkansas is stink bugs heavy at the edge of fields, he says.

“Last year, in one field around Hughes, I saw stink bugs 150 feet into the field. The plants stayed green clear through to frost and never generated a pod.

“No-till fields tend to draw stink bugs too. Primarily what I’ve seen is delayed senescence of leaves and larger stems (because of the toxins secreted by stink bugs when they hit plants). Plants just keep blooming but never put a pod on. This was commonplace last year. I think the damage will be apparent when we get to pod fill. When the determinates start trying to make a crop, the problems will show.”

‘Mohawk’ corn

McVay is also finding rootless corn throughout the Delta. Such corn is normally seen when seed is planted too shallow.

“This year, no-till has been tough for rootless corn because the ground was wet for so long. The roots didn’t go deep and if they did, they could have drowned. So that meant shallow root systems. The plants kept making stalk, but when the wind blows now the plants fall over. That leads to ‘goose-necking’ where the plant tries to right itself,” says McVay.

The other thing McVay has seen – and it’s been severe in some no-till fields – is where growers had to plant into a slit when the ground was wet. Roots grew down the slit but were unable to break through the sidewalls because of compaction.

“When a bricklayer works, he uses a trowel that makes a very slick surface. That’s what happens when steel cuts through wet soil. As a result, the root masses become warped. I call it ‘Mohawk’ roots because the plants look like they’ve got Mohawk haircuts,” says McVay.

If rain comes, soils around “Mohawk” roots loosen and might be penetrable. That leads to height variability within fields. The plants able to break through the sidewalls get taller than those that can’t.

“In any year – especially when it’s wet – there’s a good chance of this happening, especially in the Delta. This season, we’re seeing it regularly,” says McVay.

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