Texas High Plains Cotton: Insects to Watch Out For

Insect pest pressure continues to be relatively light across the South Plains. The major pests to monitor closely at the current stage of crop development include cotton bollworms, plant bugs, and stink bugs. Cotton bollworm population remains extremely low in cotton. I have noticed some lygus activity, but the populations are well below threshold. At this stage, stink bugs are the primary insects on my radar.

We deal with several species of stink bugs in cotton, with the most common being the green stink bug and the Conchuela stink bug. Stink bugs are challenging to scout, especially in tall, vigorous cotton. I have observed stink bugs in several fields, but their numbers are very low, and there has been no internal boll injury detected yet. Based on my experience over the last few seasons, stink bugs often go unnoticed during August and early September, and their damage becomes apparent in the later stages of crop development when it is too late to prevent losses.

Conchuela stink bug adult

Stink bugs have piercing-sucking mouthparts and damage cotton by piercing the bolls and feeding on the developing seeds. Infestations cause economic losses through reduced yield and loss of fiber quality. Stink bug feeding can also transmit plant pathogens that cause boll rot.

External signs of stink bug feeding

Generally, stink bugs prefer medium-sized bolls but can feed on bolls of any size. Feeding on young bolls (less than 10 days old) usually causes the bolls to shed. In larger bolls, stink bug feeding often results in dark spots about 1/16 inch in diameter on the outside. These dark spots do not always correlate with internal damage, such as callus growths, warts, or stained lint. There may be several spots on the outside of a boll without internal feeding damage.

Decisions to treat stink bug infestations are best made based on the percentage of bolls with evidence of internal damage (warts or stained lint associated with feeding punctures). To use this technique:

1. Remove about 10 to 20 bolls, 1 inch in diameter (about the size of a quarter), from each of the four parts of the field, avoiding field edges.

   

   Boll wall warts (Photo: Pat Porter)

2. 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.
3. Check bolls with visible external lesions first to determine if the internal damage threshold has been met, as bolls with external lesions are more likely to be damaged internally.

   

   Lint staining caused by stink bug feeding
   
   

 

Alternatively, detection of one or more stink bugs per 6 row feet can also be used as an action threshold.