Stink bugs show up early this year

Frances Gould, Schultz, Bruce, Benedict, Linda F.  |  11/13/2013 11:22:22 PM

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A redbanded stink bug was found on June 3 in a soybean field at the South Farm of the Rice Research Station near Crowley. (Photo by Jeff Davis)

LSU AgCenter entomologist Jeff Davis found stink bugs in agricultural fields earlier than expected this year.

"We found them active in clover reproducing during the winter. They are not supposed to be active at this time," he said.

More alarming, though, was finding redbanded stink bug nymphs on June 3 on soybeans only 8 inches tall, and adult redbanded stink bugs in 12-inch-high soybean plots. Both discoveries were at the South Farm of the Rice Research Station in Crowley, where he rarely finds any stink bugs.

If left unchecked, the redbanded stink bug can cause damage so extensive that farmers may lose an entire soybean field, Davis said. The redbanded stink bug is the No. 1 pest of Louisiana soybeans.

"We are not supposed to be finding stink bugs in Louisiana this early in the vegetative stage. All the literature says we won’t find them until pods have developed," Davis said.

He is working this year with a new sampling device that uses a leaf blower on a backpack to suck insects from soybean plants. He said the vacuum finds insects often missed with sweep nets, which can also damage small plants.

Davis has two studies funded by the Louisiana Soybean and Grain Research and Promotion Board. The first study examines possible traits that make some varieties of soybeans undesirable to soybean pests, while integrating natural enemies of the pest and insecticides. The second study is aimed at determining when stink bugs move into a soybean field and how they survive winters.

Clovers appear to be a bridge species that harbor stink bugs until soybeans are growing. Farmers who use clovers as cover crops should be aware that this practice could increase populations.

Two other insect pests also could be problems for Louisiana soybean growers, Davis said. The kudzu bug was found in Madison and Tensas parishes, and the brown marmorated stinkbug has been found in Texas.

To detect movements of those two insects in Louisiana, small plots of 10 high-yielding soybean varieties were planted at several research stations and sampled weekly.

"We use them as our early warning system," Davis said.

Yield and quality will be examined after harvest, he said. Half the research plots will be sprayed, and half will be left unsprayed for comparison.

Fortunately, the brown marmorated stink bug is not in Louisiana yet.

Alabama and Georgia soybean farmers have found the kudzu bug in their crops. Yield losses in nontreated fields could be as high as 40 percent, Davis said, but several insecticides are available that are effective against the insect.

Davis also will be monitoring soybean insect pests for insecticide resistance. He said some populations of stink bugs were showing resistance to recommended products last year.

Bruce Schultz

(This article was published in the 2013 Louisiana Soybean & Grain Research & Promotion Board Report.)

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