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This is Jack Bacheler, Extension Entomologist at NCSU with the Wednesday Cotton Insect Hotline tape, although today is Wednesday, May 20.

Three county agents and one consultant called within the past two days with the same question: What’s this cold weather doing to cotton’s susceptibility to thrips damage? That's a good question, and to some degree depends on when the cotton was planted and what at-planting insecticide approach was used.

Most of the cotton planted during the last few days in April or during the first few days in May has actually fared well this year on average, with good soil moisture and at least decent temperatures until this past Sunday, May 17. Cotton planted during the past 7-10 days, including several of our tests at Rocky Mount planted on May 11, is generally coming up to a fair to good stand but is struggling now with recent nighttime lows in the mid-40’s - temperatures shared with most of the state. On the good side, after today, highs in the low to mid 80’s and lows in the low to mid 60’s are predicted over most of the state for the next week. This pattern should help with cotton grow-off, yet not trigger heavy thrips migrations from rapidly drying down hosts that we would have expected from dry weather with temperatures in the 90’s. As we mentioned last week, thrips levels so far this spring have been on the light side.

For now, remember that the uptake of both aldicarb (the active ingredient in Temik) and the insecticides in seed treatments has been slowed during these past few days and cotton seedlings have been growing off very slowly during a vulnerable stage. Under these conditions, migrating thrips levels are lower, but the plants remain in this very susceptible stage for much longer. In the case of Temik, if the cotton was planted within approximately the past 3 weeks, with soil and air temperatures warming up significantly today and tomorrow (May 20 and 21), the uptake and decent thrips control should resume. The amount of rain that most parts of the state received in the past few days is not enough to wash the aldicarb out of the root zone. In the case of seed treatments, 21 days from planting will usually signal the end of thrips activity irrespective of weather.

Producers and scouts should be advised to look at the bud areas of seedlings as the temps warm up to see if immature thrips are getting started. This process will be much more accurate with the assistance of a hand lens, or by beating some seedlings onto something like an index card. If you see more than an average of approximately 1-2 immature thrips (w/o wings) per plant, and the newest leaves look deformed, a foliar spray is probably needed.

Let’s keep our fingers crossed that good soil moisture and warm temperatures are the rule for the next two weeks as we push toward the “thrips-safe” 4-5 true leaf stage.

We’ll provide next week’s cotton insect tape on Wednesday, May 27. See you then.