New Pest Threatens Soybean Producers

Jack L. Baldwin, Merrill, Thomas A.  |  4/19/2005 10:28:58 PM

News Release Distributed 09/09/04

Louisiana soybean producers are facing a new type of stink bug that is equally damaging but more difficult to control than the green and brown stink bugs they are accustomed to fighting, says LSU AgCenter entomologist Dr. Jack Baldwin.

Casually referred to as the red-shouldered stink bug, the new threat is more specifically known by its scientific name of "Piezodorus guildini," according to Baldwin.

"People call it the red-shouldered stink bug, but is not the correct common name for this species," Baldwin says, explaining, "It acquired the misnomer because of its appearance."

Adults of this bug have a reddish-orange band across the back, right behind the head, which is a common characteristic of another stink bug species, Baldwin says. That’s what’s led to the confusion.

He says the new ones threatening Louisiana farmers – Piezodorus guildini – also are light green and about 2/3 the size of a southern green stink bug.

"Piezodorus guildini is a more established pest of soybeans in South America, especially in Brazil," the LSU AgCenter entomologist says. "And research from South America indicates it is equally, if not more, damaging than the southern green stink bug."

The stinkbugs damage soybeans by reducing yield and quality. They also can cause leaf retention.

"While Piezodorus guildini is not a new stink bug species to Louisiana or the United States, it had never been documented as a major pest of soybeans here," Baldwin says.

This stink bug was first observed in light numbers in South Louisiana at the LSU AgCenter’s St. Gabriel Research Station in 2000. In 2002 and 2003, populations of the pest first became high enough for insecticide testing, according to Baldwin, who says these results were not alarming, but they did indicate it was generally more difficult to control than the southern green stink bug.

"Heavy populations were first reported this year from southern and southeastern Louisiana – where early-maturing soybean fields required multiple applications for, at best, mediocre control," Baldwin says. "Populations of Piezodorus guildini have since spread into the southwestern soybean parishes and into the Lower Delta parishes of northeastern Louisiana."

The LSU AgCenter entomologist says environmental conditions conducive to an epidemic year and its general tolerance to most insecticide treatments are probably the causes for this stink bug becoming a major pest in 2004.

"LSU AgCenter research in 2004 indicates that acephate is the most effective insecticide for control of Piezodorus guildini," Baldwin says, adding, "Because of the large acreage of late-planted soybeans in some areas of the state, a crisis exemption was recently declared for the use of acephate on soybeans."

That exemption was granted by the Louisiana Department of Agriculture and Forestry for the use of acephate on soybeans between Sept. 3 and Sept. 19.

Baldwin says methyl parathion at high rates also gives good initial control of this species of stinkbug, but that treatment lacks any effective residual control.

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Contact: Jack Baldwin at (225) 578-2369 or jbaldwin@agcenter.lsu.edu
Writer: Tom Merrill at (225) 578-2263 or tmerrill@agcenter.lsu.edu

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