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Stink bugs move through soybeans

Even with the threat of Asian rust and concerns about late planting, the big story in Louisiana soybeans is the red-shouldered stink bug. Some eight to 10 parishes have been hit by the pest.

“Inundated doesn't come close to describing how many we've got in some areas,” said David Lanclos, Louisiana Extension soybean specialist. “Through discussions with (Louisiana Extension entomologists), there are some common things surrounding the pest. One is a perception that Orthene isn't working well on them. But a pound of Orthene is a potent treatment, especially for stink bugs. We feel it probably isn't the product that's the culprit but the spray technology.”

When spraying, everyone worries about drift. Because of that many still employ air-induction nozzles.

“If you're going after this pest, use a flat-fan or hollow-cone nozzle. And use it at a high gallon-per-acre rate under high pressure.”

The stink bugs are nothing new to Jack Baldwin, Louisiana Extension entomologist. “The recurrence of red-shouldered stink bugs is similar to last year,” said Baldwin. “But this time, we're seeing them much earlier in the season. The stink bugs have been found very early. We've found them in plants prior to bloom. They're certainly in our soybeans now.”

Red-shouldered stink bugs have been present in Louisiana at least since 2000. “Researchers at the St. Gabriel research station (in southern Louisiana) have seen this pest for a few years now. But last year was the first time we had serious control problems with it.”

The problem appears to originate in the state's southern “sugarcane parishes. That's where we first saw numbers building last year when they appeared in late July and early August.”

This year, Baldwin has received reports of the stink bugs as far west as Acadia Parish. They've also moved into central Louisiana and the lower Delta in the northeast. Still, it appears the “largest onslaught” is occurring in south Louisiana.

“They overwintered very successfully,” said Baldwin. “We started finding these stink bugs in alternate hosts in February and March. By May they were beginning to move into soybeans. So we've had our eye on them for a while.”

Two companies have 24Cs for Orthene/acephate in Louisiana. Field reports from last year “said (the products are) effective,” said Baldwin.

To combat the pest, which causes plant damage similar to its more common brown and green cousins, the state Extension Service has lowered threshold numbers. “Now, it's 24 per 100 sweeps,” said Baldwin.

Due to the pest, how many sprayings are in store for Louisiana producers?

“We don't know but we hope the knowledge we gained last year and Orthene it will keep sprays to a minimum,” said Baldwin. “This is just something else producers have to be concerned with. The fact insecticides are limited is an added burden. In some respects, though, even though it's occurring earlier, we're more on top of it. By being in that position, hopefully we'll be better off.”

Regardless of cultural practice or product, Lanclos is most alarmed with the need to spray so early. “It's about two months earlier than we've ever sprayed before. That's scary.”

In the case of red-shouldered stink bugs in soybeans, economic fears trump all others. “It's expensive controlling this pest,” said Lanclos. “If we're already spraying at such an early growth stage, it's setting up to be financially catastrophic. We're potentially looking at four or more sprayings. Eventually it gets too expensive to protect the crop. I pray we won't reach that point.”


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