The redbanded stink bug took a year off from assaulting Louisiana soybeans in 2010, and the question on grower minds today is whether or not it will return in 2011. According to LSU AgCenter entomologist Jeff Davis, the answer may start to reveal itself as early as April.

Davis spoke at the Louisiana Agricultural Technology and Management Conference in Alexandria La. The conference was sponsored by the Louisiana Agricultural Consultants Association.

No doubt, the redbanded stink bug is the major stink bug pests in Louisiana, according to Davis. Studies conducted in 2009 on soybean plots at the Ben Hur research station indicate that 63 percent to 81 percent of the stink bug species present were redbanded stink bug.

But winter temperatures and spring weather can have a significant impact on in-season populations, according to Davis.

For example, from October 2008 to June 2009, the Red River research station recorded only one hour of temperatures at 20 degrees or below. None of the other stations in the state recorded any hours at 20 degrees or below. The following year was a heavy redbanded stink bug year.

During the same months in 2009-10, however, the St. Joseph station recorded 14 hours at 20 degrees or lower, the Ben Hur location recorded 10 and the Dean Lee station, 5. No hours below 20 degrees were recorded at the New Iberia station in 2010. The following season, only New Iberia reported significant infestations of redbanded stink bug, although they did appear late in the season.

So far this winter, the Red River station has reported 10 hours at 20 degrees and below, the Dean Lee station, 4 and the St. Joseph station, 14.

From this preliminary data, Davis calculates that for each hour at 20 degrees or less, there is an 8 percent decline in redbanded stink bug population. “It will be interesting to see what level of redbanded stink bug populations we have in 2011. Indications are that we may have another low year.”

Drought conditions in April can also impact populations of redbanded stink bugs, according to Davis. “This is when they are emerging from their overwintering sites and looking for secondary hosts to feed on. There are no soybeans podding at that time, so they’re looking for clovers or any other legumes they’ll be able to feed on. In the droughty conditions of April last year, that vegetation did not emerge or they were cut off early and redbanded stink bugs didn’t have a lot to feed on before they moved into soybeans.”

The redbanded stink does have an edge over other stink bugs in that it is simply harder to kill, noted Davis. Adult vial tests indicate that an eight-fold increase in the rate of Karate is required to kill a redbanded stink bug versus a southern green. Nine times as much acephate was required to kill a redbanded stink bug versus a southern green.

“Pyrethroids don’t work as well as they do on southern greens,” David said. “Organophosphates don’t work as well and neonicotinoids don’t work as well either.

Tank mixes are more effective, according to Davis, and include Endigo (which contains thiamethoxam and lambda cyhalothrin), Leverage (which contains imidacloprid and cyfluthrin), and cyfluthrin and acephate.

Davis recommends that growers budget for three stink bug applications per year. “We want you to rotate those products because we don’t want to build resistance to a single product. We need to maintain susceptibility to these products.”