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This is Jack Bacheler, Extension Entomologist with North Carolina State University with this week’s cotton insect update. Today is Wednesday, May 24.
Thrips really began asserting “themselves” this week. All of our May 1 and 2 planted seed treatments, with the exception of one seed treatment with a mega-rate of imidacloprid, were pretty banged up today at the Rocky Mount research station. However, damage to the untreated check plots were certainly no worse so far than in an average year. If not already sprayed with a foliar insecticide following a seed treatment, this would be a good time to monitor seedlings for bud damage and live thrips. With most of this cotton only approaching 2 true leaves, we are likely in for an additional week or a little longer so before we approach 5 true leaves in this early May planted cotton. We have received no calls through today of poor thrips control. However, if difficult to control western flower thrips show up as a problem, we would normally expect this to occur about now or within the next week, or so.
On the plus side, we are now in a period of warmer weather with generally adequate moisture levels in many areas of the state. The more rapid seedling growth resulting from these conditions should shorten the present window of vulnerability to thrips damage.
On the kudzu bug front, the colonizing of early planted soybean by kudzu bug in GA, SC and NC was both a surprise and a wakeup call to check soybean seedlings for the presence of these pests. Although no treatment thresholds have been established yet for kudzu bugs on early soybeans, sweep net samples taken from representative areas of early soybean fields will at least put producers in the ballpark of whether damaging populations may be present. The few soybean fields that I have swept this week averaged approximately 1 to 2 kudzu bugs per 100 sweeps, certainly well below any threshold that may be established. However, the images sent out by Jeremy Greene last week dramatically showed that kudzu bug levels in some early soybean fields have reached alarming levels during the past week. My guess is that 1-2 or fewer kudzu bugs per 15 sweeps would probably not result in economic damage, though that’s a seat-of-the-pants guess at this point. We do not recommend routine spraying following the finding of a few kudzu bugs, as this may be of limited value and the resulting disruption of beneficial insect can greatly enhance subsequent caterpillar establishment. For the later season anticipated large flight of kudzu bugs into soybean, expected here in late July or early August, the treatment threshold of 15 nymphs per 15 sweeps developed in GA and SC is recommended.