Redband stink bug research continues

Frances Gould, Morgan, Johnny W.  |  11/20/2013 3:02:48 AM

LSU AgCenter entomologist Dr. Jeff Davis uses his sweep net to collect insects in a soybean field at the AgCenter’s Central Research Station in Baton Rouge. Using the numbers of insects collected and other data, he is able to determine the optimum time to spray chemicals to decrease insect pressure. (Photo by Johnny Morgan)

The adult redbanded stink bug is an insect that causes tremendous damage by eating the soybean seed before harvest. The damage can be so severe in some fields that growers have nothing to harvest. In others, damage from this pest can result in grain being rejected by the elevator. (Photo by Bruce Schultz)

Progress is being made, but research continues on the redbanded stink bug problem in soybeans across Louisiana.

LSU AgCenter entomologists Dr. Jeff A. Davis and Dr. B. Rogers Leonard are evaluating integrated pest management strategies to manage this pest and reduce its potential damage to soybeans.

Formal experiments are being conducted on research plots from New Iberia to Bossier City and back to Winnsboro. As part of that research, the LSU AgCenter scientists are looking at the threshold numbers of the pest that actually cause yield and quality losses, Davis said.

"We are continuing this study to determine the most effective economic threshold, biological control, host plant resistance and chemical control strategies for the redbanded stink bug," Davis said.

Leonard said this insect has a built-in tolerance to a number of the insecticides commonly used to control most stink bug species, so growers must spray more often to manage redbanded stink bug infestations.

"The problem with this intense spraying is if we keep using the same insecticides, the pest could become resistant," Davis said.

Another problem caused by increased spraying is killing beneficial insects that keep other pests from becoming established in the fields, Leonard said.

To avoid these problems, manipulation of planting dates and new varieties are being looked at as alternatives.

"We currently are looking at some of the new Pioneer varieties, which have shown lower infestations of redbanded stink bugs compared to some other varieties," Davis said.

The redbanded stink bug is able to inflict an amazing amount of damage to a soybean crop because of the way it uses its piercing/sucking mouthparts, according to Davis.

"This pest injects enzymes into the bean’s seed that dissolve the seed and then allow the stink bug to remove the liquid almost like a milkshake,"
Davis said. "They are able to pierce harder surfaces than you would expect."

Davis said this pest puts high stress on soybean plants, causing them to stay green when the crop should be maturing and thus decreasing harvest efficiency.

"Sometimes the damage is so bad there is no reason to even harvest," Davis said. "There’s just nothing there."

Redbanded stink bugs don’t just cause yield losses from feeding; they also cause entry points for fungi into the seed pods as well, Davis said.

With the most severe instances of seed injury, the damage is so bad the beans are turned down by the grain elevator. "When this happens, about the only use is (processing) for hog feed," Davis said.

So far in 2011, the highest infestations of the pest were in the Jeanerette area, Davis said, adding that might be because a number of cane growers are now planting soybeans on fallow sugarcane acres.

"Cane growers are taking advantage of the good price on soybeans right now by planting in late March and early April and harvesting in early August in time to put plant cane in," Davis said.

Stink bugs are a problem in the cane-growing areas of the state because of the warm, moist climate and because the soybean crop is planted earlier in those areas than in many other areas of the state. In addition, alternative hosts for the stink bugs may be more available during the spring months and play a role in building populations prior to them immigrating into nearby soybean fields.

"Surprisingly, the numbers are low in the Delta this year," Davis said, explaining the cold weather this winter along with the drought conditions through much of the year may be causing the suppressed numbers.

But he warned low numbers the early part of the summer may leave a false impression, since those numbers were likely to increase across the state during late July and early August.

Meanwhile, the research project is evolving. The biological control survey portion of the project is ending this year, and research with border sprays already has ended.

Davis said the end goal of the project is to have an active website where growers can punch in the numbers concerning stink bugs found in their fields and get back a recommendation on when they need to spray.
Johnny Morgan

2010-11 funding for these projects:
$67,968 (soybean)

(This article was published in the 2011 Louisiana Soybean & Grain Research & Promotion Board Report)

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