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This is Jack Bacheler extension entomologist at NCSU with the Cotton Insect Update. Today is Wednesday, August 26.

Cotton continues to shut down in an ever-increasing number of cotton fields, but some fields that have received good or excessive moisture are still attractive to stink bugs. One example of this is our stink bug threshold test in Wayne County where the cotton is just over 5 feet tall and the quarter-sized bolls in the untreated checks are running right at 40% internal damage. However, even in this case, the dynamic threshold is within a few days “calling for” using 50% internal boll damage to quarter-sized bolls as the spray trigger. That’s because such a high proportion of the bolls are older that 3.5 weeks and can no longer be damaged by stink bugs.

In general, very few cotton fields are still susceptible to economic damage from stink bugs, and treatments from here on out can only be justified from late maturing fields with very high stink bug damage to young bolls.

Another thing to watch as the crop matures is that some of the purplish dots that always show up on mature bolls look like stink bug damage. Additionally, even though a boll older than 3.5 weeks can no longer be damaged by stink bugs, stink bugs can still cause the external spotting by their feeding. So some producers may think that they’re getting hammered by stink bugs are presently surprised to find their cotton opening normally. One final note is that the degree of stink bug damage to bolls is influenced by fall weather. The drier the harvest season, the better.

Most of our actual damage from stink bugs for 2009 will reveal itself as cotton begins to open. This is most easily appreciated when open cotton suffers from significant hardlock under dry conditions. It’ll be interesting to see how this year crop fares with stink bug damage.

We’ll have the next report in a week on September 2. See you then.