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This is Jack Bacheler, extension entomologist at NCSU with the Wednesday cotton insect update. This is late Wednesday afternoon, August 20, 2008.

A significant portion of our cotton continues to cutout rapidly, with a number of fields well past the stage of being either attractive or vulnerable to bollworms and stink bugs. Any cotton which has reached the stage where small terminal squares and blooms are hard to find in representative areas of cotton fields is no longer susceptible to bollworm, stink bug or plant bug damage. This was the case in a Bertie County stink bug threshold test yesterday where blooms were getting scarce, the upper square retention had dropped to less than 10%, and the recent stink bug damage to quarter-sized bolls in the untreated check had dropped to approx. 2%.  In our Wayne County stink bug test this morning, where moisture has been very good throughout the season and the cotton is 5+ feet in height, stink bug damage had averaged just under 30% internal boll damage in the untreated over the past three weeks. The untreated check this morning was still at 30%, indicating that decent stink bug populations may be present in the high moisture or late maturing situations. However, because the cotton was in its 6th week of blooming in this test, the 30% internal boll damage threshold would have just barely been met in producer fields.

On very rare occasions, beet and/or fall armyworms can migrate into North Carolina cotton fields in high enough numbers to cause economic damage to conventional and Bollgard cotton as late as the first week in September. Bollgard II and Widestrike cotton varieties are not susceptible to this damage. We have not been made aware of any economic damage by the above two pests, though both species are present in some cotton fields at low levels.

With our 2008 year’s cotton crop rapidly coming to a close, this would be a good time to plan on attending the September 10 Cotton Field Day at Rocky Mount, beginning with Registration at 12:30 and the tours at 1:30 p.m. This year’s tour stops will include a look at new weed management systems, managing difficult thrips problems, defoliation strategies, bloom-time fungicide applications for boll rot and hard lock control, fertilizer cost savings strategies, underappreciated soil compaction problems, and OVT tests of current and promising varieties.