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NC Cotton Insect Update May 2, 2012

This is Jack Bacheler, extension entomologist at North Carolina State University with the Wednesday May 2 Cotton Insect Update. We still don’t have much to report this week on the cotton insect front, though serious cotton planting is now underway in North Carolina, with generally fair to good moisture levels and warm to hot daytime temperatures. However, much of our acreage is drying quickly.

With a warm winter and early spring, tobacco thrips appear to be early and perhaps on the high side so far, although we’re a week or more away from getting a handle on the possible impact of thrips on cotton seedlings this spring. In a few past years, we have found as many as 15 thrips per seedling prior to the initial expansion of the cotyledon leaves. This may be one of those years.

Here are a few points to keep in mind over the next few weeks.

1. In NC, expect greater potential thrips problems in cotton planted before approximately May 10 than in cotton planted after that time. Slower seedling growth with earlier plantings typically accounts for most of this damage.

2. In replicated tests conducted in thrips-prone areas of NC, cotton planted after approximately May 15 often does well without a foliar application following a seed treatment. This is due to quicker seedling grow-off and declining migrating adult populations that often occur about the time when these late-plated seedlings are at their most vulnerable 1st true leaf stage.

3. If a foliar application is need following a seed treatment (most often the case in NC), an application just before or during the first true leaf stage is far more effective against thrips than one applied during the second true leaf stage or later.

4. Unfortunately, both extended hot dry weather and cool wet conditions can limit the uptake of at planting insecticides, including seed treatments, granular insecticides, and in-furrow sprays.

5. On the other hand, warm moist conditions favoring rapid seedling growth shorten the time of seedling vulnerability to potential thrips damage.

Hopefully by this time next week or early in the following week, we’ll have a clearer picture of how our 2012 ‘thrips season’ is shaping up.

We’ll see you again next Wednesday, May 9. See you then.