Being No. 1 typically is a good thing, except when it comes to damaging insect pests in cotton. According to Mississippi Extension entomologist Angus Catchot, the tarnished plant bug (TPB) is now the No. 1 insect threat, particularly in the Delta region of the state.
Dr. Jeff Gore, research entomologist at the Delta Research and Extension Center (DREC), attributes the high cost of tarnished plant bug control (up to $100 per acre in some areas) in addition to pricey early season sprays for spider mites as the main reason for the reduction of cotton acres in the Delta.
For Mississippi producers who are growing cotton, Gore points out that 10 to 15 years ago, the blanket recommendation was to begin making applications for TPBs before first flower. Today, those early applications aren’t returning as much as they used to because so many applications are being made later in the year.
“A lot of our research shows more yield loss from larger late-season populations of TPBs compared to early season populations,” Gore says. “There-fore, rather than making an application based on crop stage, apply the commonly used insecticides, such as the neonicotinoids, if square retention drops to about 80 percent. This will save one to two pre-flower applications that can be used once the cotton is flowering and provide a greater return for producers.”
The Mississippi researcher notes that last year in Louisiana and Mississippi, a pre-flower application of Diamond insect growth regulator, which is active on nymphs, was made about the third week of squaring when large numbers of TPBs were moving out of corn or other wild hosts into cotton. This strategy translated into about a 150-pound lint increase.
Breaking The Cycle
For farmers who have both cotton and corn, Catchot recommends minimizing cotton/corn interfaces.
“Where this isn’t an option,” he says, “pay particular attention to scouting adjacent to corn. Before the plant bugs begin to move across the entire cotton field, it may be advantageous for farmers to make a couple of extra border treatments next to the corn.
“When we get into really heavy plant bug situations after bloom, producers have to break the cycle by tightening the spray intervals as well as incorporating Diamond insecticide in with an adulticide to break the cycle,” Catchot says.
“Instead of a seven- to 10-day spray interval, go to a four- to five-day interval. Good timing for the Diamond application would be between the third week of squaring or first bloom when the first nymphs begin to show up.”
As the crop moves into bloom, the Mississippi entomologist recommends using a mixture of products or pre-mixed products, such as Bidrin XP, Endigo or Leverage 360. If producers are making acephate sprays, Catchot recommends adding a pyrethroid.
A Consultant’s Perspective
New Strategies Against Plant Bug
Joe Townsend, a Mississippi Delta crop consultant, says that where cotton acreage has increased and corn and soybeans are not planted close by that treatments for TPBs are reduced.
“In other words,” Townsend says, “we are spraying plant bugs at eight percent, whereas a year ago at this time in the same field, we had to spray for plant bugs because populations were at 32 percent. We’re still having to treat, but populations are much less this year where we have higher concentrations of cotton acres.”
One strategy that Townsend recommends in the effort to hold TPBs at bay is destroying alternate hosts such as coreopsis, Queen Anne’s Lace and blooming rye grass, which produce tarnished plant bugs that end up in cotton fields. Once sprays begin, he also is conscious of what products go out.
“Today, we have a bigger arsenal of plant bug materials than we did a few years ago, but we still have to watch the legal label requirement as to the total amount of a given product that can be applied on a field during the course of the season,” Townsend says. “We continue to switch up products and seldom ever repeat the same application back-to-back.”
Although it’s clear that the tarnished plant bug may have muscled its way into Mississippi’s “worst cotton pest” position, industry experts and cotton producers continue to expand the playbook looking for ways to reduce the pest’s negative impact on the state’s cotton crop.
Contact Carroll Smith at (901) 767-4020 or firstname.lastname@example.org.