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Aphids top concern in Arkansas cotton

Having “put up” so many tobacco budworms last fall, Arkansas cotton fields have been remarkable free of the pest in recent weeks.

“Thankfully, following some really high catch numbers early, trap counts for tobacco budworms are down right now,” says Gus Lorenz, Arkansas Extension entomologist. “The south half of Arkansas is trap-catching a minimal number of budworms. We may face problems further on, but there's a lull in the budworm action right now.”


Unfortunately, there are other concerns.

In the southern part of the state — “say Lincoln County on down” — producers have seen a spike in bollworm trap counts. Consultants are beginning to report white eggs in the fields associated with those high counts.

“I've spent a lot of time around Pine Bluff the last few days, so I've been kicking up my fair share of bollworm moths,” says Lorenz. “We're in the early stages of this population, so it's difficult to say how it will turn out.”

In the last couple of days, several fields Lorenz has walked have been at or just below threshold. He says there's no indication the situation will improve.

“What we've got going for us is that the majority of the cotton is Bollgard. On top of that, most of the cotton isn't blooming since we have a very late crop. On pre-bloom cotton, Bollgard does a pretty good job on bollworms. It's much better on bollworms pre-bloom then it is after.”

Aphids, thrips plant bugs

The thing that concerns entomologists now is the statewide aphid population. Aphid numbers continue to boom. Lorenz thinks it has a lot to do with Arkansas' slow-growing cotton crop.

“We're still treating this crop for thrips! It's almost unbelievable to think that we're still treating thrips in the later portion of June. That's a perfect indication about how late the crop is,” he says.

Many producers are using a broad-spectrum insecticide to treat thrips. That approach is knocking out beneficials and is a factor in why aphid numbers are so high.

“We're in a cycle that benefits aphids. The aphid fungus will show up in a few weeks and I hope it will take a bunch of them out before a lot of spraying is required.”

Plant bugs have also been bad.

“The biggest thing we need to do with this late, young crop is to maintain fruit set at around 80 percent. We don't want to do anything to delay maturity. Everyone needs to tighten their thresholds a bit and keep as much fruit as possible.”

It's a delicate balance, admits Lorenz.

“You don't want to try to save everything, but you also want to protect the fruit that's there. It's damned-if-you-do or damned-if-you-don't. If you keep too much fruit and it turns off hot and dry, the plants will pitch fruit like crazy. At the same time, we've got a late crop and need to retain the early fruit as best we can to keep from delaying the crop further.”

Grape colaspis

A large grape colaspis population also concerns Lorenz and colleagues. More and more of the pest has been seen over the last couple of years. “A lot of rice has been dinged by this pest, and now it's starting to show up on soybeans.”

The larva of the tiny beetle lives in the soil and feeds on a plant's roots. Areas within some counties — Woodruff, St. Francis, Lee, Monroe and part of Prairie — have chronic problems with grape colaspis.

“We're trying to come up with solutions. Colaspis has always been around, but it seems to be getting worse.”

In samples pulled from around Hunter (just north of Brinkley, Ark.) “very high populations” are being found in the soil. Physical symptoms of plants hosting the bugs are very similar to plants affected by cyst nematodes. Grape colaspis shows up more in fields repeatedly planted in soybeans or rice.

“The Icon seed treatment has done a good job of controlling colaspis. But word is that EPA may soon pull Icon because there are problems with the chemistry getting into crawfish. So the label could be jerked for that use,” says Lorenz.

Corn borers

“North of I-40, we're in pretty good shape with corn borers. There's not a bunch of activity in the fields I've looked at,” says Lorenz

While he's aware that higher numbers of borers are being seen in Louisiana and the southern half of Arkansas, Lorenz isn't terribly concerned over the pest thus far this season.

A recent, quick survey done over the areas of the state where there is normally corn borer pressure shows hot spots harboring the pests' first generation, says William Johnson, Pioneer field sales agronomist. But since most corn was planted prior to April 10, farmers can look confidently to historical precedent.

“That precedent shows that the corn crop outruns the second borer generation before it can do much damage,” says Johnson. “The next flight is expected around July 10. By that point, ears should be developing and borers won't be as large a concern.”

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