Tarnished plant bug Ben Thrash, University of Arkansas
Hot weather can often help control insect pressure. But cotton, corn and soybean producers needed plenty of assistance in taming tarnished plant bugs, stink bugs and other insects in the warm 2022. To be prepared for their 2023 production, entomologists advise growers to have a well-planned insecticide program ready to roll.
Tarnished plant bugs (TPB) are considered the most economically important insect pest in cotton across the Midsouth. Many crops have been stained by their presence. Adult TPBs are typically more abundant during cotton’s pre-flowering stage. Focus shifts to nymphs during flowering.
“Depending on the year, fruit damage may start early,” said Whitney Crow, Mississippi State University Extension entomologist. “TPBs prefer to feed on squares instead of small or medium bolls. Square damage or loss directly impacts yield and can occur throughout the fruit set.
“Damaged squares that do not abscise often develop into flowers that have malformed anthers. Damage to anthers that is greater than 30% can cause issues with pollination and lower yields.”
Brown stink bug (Angus Catchot, MSU)
Plant bug management is expected to become more efficient when regulatory approval is granted for the ThryvOn technology. Reams of university and private research studies indicate the Bt technology will provide tolerance to plant bugs, as well as thrips. Until then, TPB control is possible, with various cultural practices and insecticide rotation, Crow said.
Crow and her MSU associates indicate that an average of two to four insecticide applications are needed for the best TPB control, depending on the year and the location. “Results from our research in the Midsouth show that TPB management is best achieved with a few insecticides,” Crow told Farm Press. “They are Diamond (novaluron), Transform (sulfoxaflor), Orthene (acephate) and Orthene plus Brigade (Bifenthrin).”
Scouting for TPB begins at the first square to detect adults. After three weeks, sweeps are made to identify adults. The economic threshold is two to three TPBs per sweep or drop cloth sample. If the threshold is met early, Crow said Diamond should be applied at the third week of squaring at a rate of 6 oz. per acre.
Green adult stink bug (Scott Stewart, University of Tennessee)
At bloom, scouting shifts to drop cloths to detect nymphs. If threshold is met, rotate treatments of Transform applications at 1.5 oz., Orthene at 12 oz., or Orthene plus Brigade at 12 oz. + 6.4 oz. Bidrin can be used in place of Orthene at a rate of 8 oz.
Crow says growers should measure the costs of chemicals in developing a TPB control program. With the potential for tight chemical supplies again for 2023, dealers should be contacted to determine insecticide availability.
Sound cultural practices can help growers manage TPB. They include sound fertility, and management of alternate host plants, such as ditches with weedy hosts.
Stopping stink bugs
Along with TPBs, stink bugs also held their own in attacking corn, soybeans and cotton in 2022. Numerous treatments were needed to keep them beaten back. “Stink bug populations are often higher following mild winters,” Cross said. “Higher populations have been detected early in the season, resulting in increased control.”
Redbanded stink bug (Angus Catchot, MSU)
There are several stink bug types. The most common are brown, green, southern green and redbanded. In corn, brown stink bugs often feed in the whorl of young plants at about 2 ft. tall, or on developing ears before silking. This can cause plant stunting or plant death. When feeding during ear development, stink bugs cause total ear loss, or what is called“cow-horned” ears.
Crow noted that the economic threshold in corn is when 10% of the plants have one or more stink bugs present. “They can be hard to find at the base of corn,” she explained. “Stink bugs are more concentrated on the edge of fields near tree lines or ditches and generally not evenly distributed across the whole field.”
Foliar application of a pyrethroid usually provides good control for stink bugs in corn. “That’s our main recommendation for them,” Crow said, adding that thorough coverage with a pyrethroid is essential in foliar applications.
For soybeans, fields may encounter browns, greens, southern greens or redbandeds. The threshold is about 4 stink bugs per 25 sweeps for redbandeds and 9 per 25 sweeps for the others.
“Redbandeds were a bigger issue in soybeans after last year’s mild winter,” Crow said. “With southern greens, greens and browns, they are only an issue up to the plant’s R6.5 stage. Damage can occur at up to R7 for redbandeds unless there are adverse weather conditions. Then we recommend treatment a little longer.”
Southern green adult stink bug (Angus Catchot, MSU)
Pyrethroids are good for controlling greens and southern greens in soybeans. For browns and redbandeds, a pyrethroid with acephate is recommended, Crow says. Of course, stink bugs can also hit cotton fields. However, Crow points out the treatments made for TPBs will usually keep stink bugs managed.
Growers are encouraged to work closely with their local Extension office, as well as seed and insecticide suppliers and crop consultants to help manage insect pressure — pressure that will most certainly be part of Midsouth crop production in 2023.
