At only about one-quarter inch in length, this diminutive spotted creature seems innocuous enough. However, the tarnished plant bug's impact on cotton production is so dire that dozens of the country's top entomologists gathered recently in Stoneville, Miss., to address the increasingly difficult task of controlling the pest.
The Oct. 22 plant bug meeting at the USDA's Agriculture Research Service in Stoneville, Miss., featured an update on much of the Cotton Belt's ongoing battle with the pest.
Cotton producers in Arkansas have seen high populations of tarnished plant bugs this year, and insecticide treatments were made weekly in many areas trying to control the pest, says entomologist Gus Lorenz.
“We experienced populations as high as 15 tarnished plant bugs per row-foot in our test plots, and it wasn't an isolated case,” he says. “There were many control complaints. We have a problem determining when in the growing season we can quit spraying and determining how much damage these insects are causing.”
The tarnished plant bug has become as much a late-season as an at-squaring problem, he adds.
“There are a lot of producers out there making those late-season applications, but the question remains, are plant bugs causing economic damage after Aug. 15? Many growers are making weekly applications of products promising plant bug control, rather than as-needed applications. We're opposed to weekly treatments, but it's a concept being pushed by some chemical companies.”
There have been incidences of resistant tarnished plant bugs, according to USDA entomologist Gordon Snodgrass at USDA's Stoneville, Miss., facility. “The resistance level to Orthene and the pyrethroids has remained at about the same level for the past six years. It goes up and down, but there shouldn't be any associated control issues. Resistant pests are in the general population and likely will remain there.”
Gordon Andrews, an entomologist with Delta Research and Extension Center in Stoneville, Miss., says, “Some people say we're spraying too much and some say we're spraying too little — I agree. It really all depends on the crop situation.”
Aubrey Harris, also at the Delta Research and Extension Center, says he's seeing tremendous variability in the levels of infestation.
Mississippi cotton consultant Herbert Jones, says some of his grower-customers sprayed for tarnished plant bugs as late as Sept. 1 this year, and he thinks it made a difference in their harvested yields.
There were many cases of field failures, he says, but they may have to do with coverage issues. In addition, he's seeing a migration of plant bugs from neighbor to neighbor.
In Louisiana, entomologist Gene Burris says, plant bugs have been a problem throughout the 2003 growing season. “We've got the boll weevil down to extremely low levels, but a lot of growers are locked in on the plant bug. It's affecting us early, mid- and late-season,” he says.
Questions remain, Burris adds, about the timeframe for recommended treatments. “We do know it's a very effective pest in removing fruit from cotton plants.”
Fellow Louisiana entomologist Roger Leonard says tarnished plant bug control is an evolving problem, and that it's becoming more of a key pest. “It has persisted late in the season, moving in and about whenever it wants. We don't have many effective tools to use against it when it becomes a problem in cotton,” he says. “The industry is focusing on products that can get a label as quickly as possible.”
While there are two classes of chemistry currently available for plant bug control, Leonard says their future availability is not assured. “If we lose one of these, we'll see many growers exceeding the allowable use limit on the remaining class of chemistry. We're just around the corner from being in a serious situation,” he says.
Tarnished plant bugs were also the number one cotton insect pest this year in Tennessee, according to entomologist Gary Lentz with the University of Tennessee.