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By Whitney Wyatt/The Red River Sun—
CHILDRESS – While the level of stink bugs in Childress County is normal for this time of year, it’s important to keep an eye out.
“Producers need to evaluate their crops, know the thresholds and only apply chemicals if they surpass the thresholds,” said Childress County AgriLife Extension Agent for Ag/Natural Resources Ryan Martin. “There is no need to waste money if they’re not at a level that will hurt their economics.”
Martin said he’s received some reports of stink bugs in cotton, and the levels are about 10 percent to 15 percent in Childress County. If he sees these numbers increase, they will start looking at chemicals for control.
Stink bugs have piercing-sucking mouthparts and damage cotton by piercing the bolls and feeding on the developing seeds, according to a release from the Texas A&M Agrilife Extension. Stink bug infestations can cause substantial economic losses through reduced yield, loss of fiber quality and increased control costs.
Although stink bugs favor medium-sized bolls, they can feed on any size boll, the release stated. Although stink bugs may feed on bolls 25 or more days old, bolls of this maturity are relatively safe from yield loss. Their 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 of bolls, the release stated. These dark spots do not always correlate well with the internal damage callus growths or warts and stained lint. There may be several spots on the outside of a boll without internal feeding damage being present.
Damage to the internal boll wall is a good indication that lint and seed are affected, according to the release. Excessive stink bug feeding causes reduced yield, stained lint, poor color grades and reduced fiber quality. In addition to direct damage, stink bug feeding can transmit plant pathogens that cause boll rot.
Stink bugs are difficult to scout, especially in tall, vigorous cotton. Adults tend to aggregate, and the distribution of stink bugs within a field may be highly concentrated, particularly along field margins. The release stated to use any of the sampling techniques such as visual inspection, drop cloth and sweep net for scouting.
However, the release stated recent research by entomologists at the University of Georgia and Clemson University suggests that decisions to treat for 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:
- 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. 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.
Once cotton has reached 450 DD60 (degree days 60) beyond cutout (five nodes above the white flower), sampling and treating for stink bugs may no longer be necessary since bolls produced after this point will not become fully mature or contribute significantly to the crop yield. However, the release stated it is possible that this value may shift slightly due to factors such as boll shading, variety and water stress.
Based on boll sampling, treat cotton with an insecticide when stink bugs are present and 20 percent or more of the quarter-size bolls have internal warts or stained lint. Use recommended insecticides to control southern green, green and Conchuela stink bugs, the release stated.