Tennessee Cotton: When To Safely Walk Away From Insects This Season

    Brown stink bug on cotton boll. Photo: University of Arkansas

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    Usually, during that first week of September, it’s time to cut fields loose, just based on typical frost dates, regardless of the maturity of that crop. We do have some later-planted fields that are really just now at cutout, meaning plants have five or more nodes above white flower.

    That starts the clock on accumulating another 350 DD60s, which typically take you out to that early September timeframe.

    What we’re trying to do right now is protect those last pickable bowls until early September when they should have about 350 DD60s and we can cut those fields loose.

    Of course, much of our cotton has been cut loose already, meaning people aren’t scouting it anymore. It has very few white flowers and has bloomed out the top. It’s at zero to one or two NAWF, and it already has accumulated well over 350 DD60s.

    But, our later planted cotton is still just sitting there at 4 to 6 NAWF and will need protection from stinkbugs, plant bugs and bollworms. Our bollworm flight is just now peaking in parts of the state. It’s not a huge flight, but we are seeing a flurry of activity a bit farther north.

    We’ve had some pretty heavy moth captures in an area that includes Crockett, Gibson, Dyer and Carroll Counties. So, later maturing fields are certainly at risk, and we need to closely watch Bollgard II fields in particular. If issues develop with bollworms, those are the fields where we’d expect it, and they might require an insecticide application farther into the month.

    On much of the crop, plant bugs are just going to damage the smaller bolls and squares now. But, a square has no alue to us now because it has very little chance of turning into a boll that makes it into the picker.

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    So, relax your thresholds on tarnished plant bugs in the latest cotton, maybe even double those thresholds. However, I probably wouldn’t do that for stinkbugs. Continue going with a threshold of one stinkbug per drop cloth. If you see stinkbugs in this later maturing cotton, I definitely would consider treating.

    You also have to take into account the bollworm situation and how many plant bugs you have in those fields. It’s certainly not impossible that you’d need to make a plant bug application in the next 7 to 10 days. But I wouldn’t base that on finding three nymphs on a drop cloth. I would base making a treatment on finding 5 or 6 nymphs on the cloth. They’re just not going to do much damage this late in the season.

    Let’s finish this crop off right and keep scouting where it matters, but 70% to 75% of the crop is past the point that we would care about insect damage.

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