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

LSU AgCenter entomologists Jeff Davis and Rogers Leonard are evaluating pest management strategies to reduce its potential damage to soybean. Experiments are being conducted in plots located from New Iberia to Bossier City and east to Winnsboro.
 
"We are continuing this study to determine the most effective economic threshold, biological control, and host plant resistance and chemical control strategies for the redbanded stink bug," Davis said.

This insect has a built-in tolerance to a number of the insecticides commonly used to control most stink bug species. 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 will become resistant," Davis said.

Another problem caused by increased spraying is the destruction of 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 are looking at some of the new Pioneer varieties, which have shown lower infestations of redbanded stink bug compared to some other varieties," Davis said.

The redbanded bug is able to inflict an amazing amount of damage to the soybean crop because of the way it uses its piercing-sucking mouth parts, Davis said.

"This pest injects enzymes into the bean’s seed, which dissolve it and then allow it 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, which decreases harvest efficiency.

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

Not only do they cause yield loss just from feeding, but they also cause entry points for fungi into the seed pod as well, Davis said.

Under 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 for hog feed," Davis said.

In 2011, the highest infestations of the pest are in the Jeanerette area. Davis said this may 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 the soybean crop is planted there earlier than in many other areas of the state. In addition, host plants may be more available during the spring months and play a role in building populations.

"Surprisingly, the numbers are low in the Delta so far this year," Davis said. It is believed that the cold weather along with the drought may be causing the suppressed numbers. However, this may be a false impression, and those numbers are likely to increase.

Davis said the end goal of the project is to have a website where growers can punch in the numbers found in their fields and be provided with a recommendation on when they need to spray.

Johnny Morgan

(This article was published in the spring 2011 issue of Louisiana Agriculture Magazine.)