Cotton fields that have accumulated 450 DD60 (degree days 60) beyond cutout (5NAWF) are generally safe from an economic damage from stink bugs. Late planted and heavily irrigated fields with fairly high number of young bolls still need to be scouted for stink bugs.
Stink bug feeding on young bolls (<10 days old) usually causes the bolls to shed. In larger bolls, stink bug feeding often results in dark spots ~1/16 inch in diameter on the outside of bolls. These dark spots do not always correlate well with the internal damage—callus growths or warts and stained lint.
Damage to the internal boll wall is a good indication that lint and seed are affected.
Base decisions to treat for stink bug infestations on the percentage of bolls with evidence of internal damage (warts or stained lint associated with feeding punctures). To use this technique:
- Remove about 10 to 20 bolls, one inch in diameter (about the size of a quarter), from each of four parts of the field, avoiding field edges.
- Break open the bolls by hand or cut them with a knife. Look for internal warts on the boll walls and stained lint on the cotton locks.
- Check bolls with visible external lesions first to determine if the internal damage threshold has been met because bolls with external lesions are more likely to also be damaged internally.
Use a 10 percent to 15 percent boll injury threshold during weeks 3 through 5 of bloom and 20-30 percent during weeks 6 or later of bloom. If using drop cloth or whole plant inspection method, detection of 1 stink bug per 6 row-feet would also justify treatment. Pyrethroids or organophosphate (e.g. Bidrin, Orthene) insecticides provide a good control against conchuela stink bug which is the primary species we encounter.
Products targeted at plant bugs such as Transform, Carbine, Diamond, and neonicotinoids will not be sufficient to control stink bugs. For the mix of stink bug and plant bugs, either Bidrin or acephate would be a good choice or a tank mix of plant bug product (e.g. Carbine, Diamond, Transform, neonicotinoids) and a pyrethroid or acephate.
Detailed list of suggested insecticides can be found here.