Thrips are staking claim as the No. 1 cotton pest in west Tennessee. And the plant bug isn't that far behind. According to Cotton Insect Losses 2002, compiled by Mississippi State University Extension entomologist Mike Williams, thrips infested 97 percent of west Tennessee cotton acreage in 2002 and reduced yield by 15,543 bales, both tops in those categories in west Tennessee.
“Thrips is probably the most important early-season pest that we have,” said Scott Stewart, Extension cotton entomologist at the University of Tennessee's West Tennessee Experiment Station in Jackson. “Ninety percent of our acreage is treated every year for thrips. Most of the treatments are in-furrow insecticides and those are pretty expensive treatments.”
Damage from thrips, can be all across the board, Stewart said. “Very often, if thrips aren't controlled adequately, it can result in replanting (which occurred extensively in 2002). Yield losses can vary from none at all to 10 to 20 percent depending on the year.”
With cool weather almost a given at planting in west Tennessee and with so much acreage infested by thrips year after year, growers often go with preventative applications of a systemic in-furrow insecticide such as Cruiser or Gaucho seed treatments or Temik in-furrow, according to Stewart. “That prevents us from having to replant and limits the amount of damage that we take.”
Stewart noted that a few farmers don't use anything at planting and apply a foliar spray if thrips infest young cotton.
The problem with going with a foliar spray only is two-fold, notes Stewart. “One is that weather may not permit you to put on the application. Second, a lot of the data suggests that even if you wait for that first true leaf when that cotton is coming out of the ground, if you've had a heavy thrips year, you could have already sustained economic damage. It can occur very quickly.”
Stewart says the data he's seen indicates that a seed treatment or in-furrow insecticide for thrips control, are pretty comparable. It becomes a preference for the grower and what system he wants.
There are a few things to consider, however, according to Stewart. If a grower has a problem with reniform nematodes, they are going to be more inclined to use Temik because Temik does have some activity on nematodes and the seed treatments do not.
In addition, in cold, wet springs, the in-furrow insecticide can play out before the cotton begins to grow. It's very common in those environments to have to spray on top of an in-furrow or seed treatment, Stewart said.
“Once cotton gets past the thrips window, which is the first two to three nodes, we usually don t have a significant problem until we start putting squares on the plant,” Stewart said. “Then plant bugs are a primary concern up until about first bloom. It's a pest that sometimes we are over-concerned about, but it certainly can be very damaging in some years and in some fields.”
According to Williams survey, plant bugs infested 93 percent of west Tennessee cotton acreage in 2002, which was second only to thrips, and reduced yields by almost 6,000 bales, fourth behind thrips, budworm/bollworm and stinkbug.
Elizabeth Pugh, who farms 4,400 acres of cotton with her father, Eugene Pugh in Halls, Tenn., has seen plant bugs rise in importance, too. “We used to chase boll weevils and bollworms. But with the onset of Bt cotton and boll weevil eradication, that's really changed. Plant bugs and stinkbugs are becoming more and more important,” she said.
The Pughs went with Centric and Trimax for the pest in 2002. “We like both of those products,” Elizabeth said. “We also like the safety (handling) issue.”
The products, which are neonicitinoids, have the same active ingredient as Gaucho and Cruiser seed treatments, Stewart noted.
The Pughs aren't sure about a direct yield benefit from plant bug control. Rather, taking out the pest itself is helping, not delaying maturity or losing fruit, Elizabeth said. “We want to keep all the fruit on it that we can. Keep the plant on track instead of delaying maturity.”
Somerville, Tenn., consultants Len and Clint Doyle like the residual activity of the neonicitinoids. “We got control up to 10 days on plant bugs and 14 days on aphids, Len said. “So that gives us a bigger window for control. So whether they're feeding or breeding, we're going to get them.”
One concern is that growers could develop a potential for resistance by over-relying on any one class of chemistry, noted Stewart. “People need to be aware that if they are putting on sequential applications in the early season for plant bugs and aphids, they have several different classes of chemistries they can choose from.”
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