As cotton reaches bloom, stink bugs can become one of the most important fall cotton insect pests to keep on a grower’s radar. They often move into fields in July, but infestations commonly become most damaging during weeks 3 through 5 or 6 of bloom, when many susceptible bolls are present.
For retailers, this is a critical window to help growers scout correctly, make threshold-based decisions and choose insecticides that fit both the pest pressure and the crop’s pre-harvest interval.
Identification and stink bug damage in cotton
There are several stink bugs in cotton that growers should be aware of, with the shared characteristics of a shield-like back and five-segmented antennae. But what matters most is recognizing the boll damage they cause.
Stink bugs have piercing-sucking mouthparts that allow them to feed through the boll wall and damage developing seed and lint. External feeding marks can be easy to miss, and they do not always tell the full story. Make sure your growers cut open 1-inch diameter bolls and look for internal symptoms, including calluses, wart-like growths on the inner boll wall, stained lint or signs of boll rot.¹
Damage to small bolls can make them die and fall off, whereas large and medium-sized bolls can have small, shallow purple depressions on the outside and a yellow to brown stain in the seed areas.
Both stink bug and tarnished plant bug damage can look identical, so make sure your growers feel equipped to differentiate between the pests and determine economic thresholds for spraying.
Dynamic economic thresholds
Beginning at first bloom, growers should scout bolls at least weekly for internal injury. They should sample 10 to 20 bolls in four random parts of a field, then examine the bolls for stained lint or raised warts.²
During weeks 3 through 5 of bloom, cotton is especially vulnerable to stink bug injury and yield loss. If 10% of sampled bolls are damaged in weeks 3-5, insecticide treatments are justified. However, consider that the threshold can be much higher outside that window, but still necessary if damage is prevalent.³
This approach helps growers avoid two common mistakes: spraying too early when the crop can tolerate more injury, or waiting too long when stink bug feeding can still reduce yield and fiber quality.
Match product choice with crop timing
When stink bug damage reaches the economic threshold, growers need an insecticide that can provide rapid knockdown of mobile populations. Retailers should help growers choose products that fit the stink bug species present, local pressure, crop stage and label requirements.
Fastac® CS insecticide can be part of a late-season stink bug management plan when growers need fast-acting control and the application fits the label. As harvest approaches, product choice must also be balanced with strict adherence to pre-harvest intervals.
Retailers should also help growers know when to stop spraying. In many cotton fields, stink bug sprays can usually stop once the crop reaches cutout and has accumulated about 450 DD60 heat units. By then, most bolls are mature enough that stink bug feeding is less likely to cause economic damage.⁴
For retailers, the goal is to help growers protect yield during the crop’s most vulnerable window without adding unnecessary late-season applications. Scout the right bolls. Use thresholds that match the crop stage. Choose products that deliver timely control. And as harvest approaches, keep PHI compliance at the center of every recommendation.
Experts are available to help you support growers in making insecticide decisions. Reach out to a nearby extension office agent or a seed company professional, such as your regional BASF representative.
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Endnotes
- Reisig, Dominic. “Don’t Forget About Stink Bugs in Cotton.” NC State Extension: Cotton, North Carolina State University, 17 July 2024,https://cotton.ces.ncsu.edu/news/dont-forget-about-stink-bugs-in-cotton/.
- “Stink Bugs.” Cotton Insect Management Guide, Texas A&M AgriLife Extension Service, cottonbugs.tamu.edu/fruit-feeding-pests/stinkbugs/.
- Reisig and Huseth. “Stink Bugs.”
- Crow, Whitney, Tyler Towles, and Don Cook. “Terminating Insecticides Applications in Cotton.” Mississippi Crop Situation, Mississippi State University Extension, 16 Aug. 2023,https://www.mississippi-crops.com/2023/08/16/terminating-insecticides-applications-in-cotton/.
