South Carolina: Three Key Insects Right Now In Cotton, Soy

    Photo: Seth Byrd, OSU Cotton Specialist

    First, reports from around the state:

    • Jonathan Croft, county agent covering Orangeburg, Berkeley and Dorchester Counties, is hearing “no complaints” in his area right now, and everyone is “just thankful for the rain.”
    • Charles Davis, county agent covering Calhoun and Richland Counties, reported “all is fairly quiet in Calhoun County. Cotton planting picking back up after the dry spell slowed us down. I have seen light thrips damage and plenty of hoppers. I imagine the rain will boost the hopper emergence.”
    • Hannah Mikell and Jay Crouch, county agents covering Clarendon and Newberry, Edgefield, and Saluda Counties, respectively, reported no problems with insects in their areas so far.
    • William Hardee, county agent covering Dillon, Horry, and Marion Counties, is seeing “some grasshoppers on corn that could be an issue for newly emerging soybean and cotton seedlings. Other than that, we are in pretty good shape. The rain has been good for thrips pressure.”

    Cotton Insects: Three For Your Scouting List

    Thrips, grasshoppers and false chinch bugs remain the most pressing issues with insects in cotton right now – and probably in that order.

    Thrips injury has been moderate to heavy in my research plots so far this season. On an injury rating scale of 0 to 5, with ‘0’ indicating no injury and ‘5’ indicating dead plants, I have hit ‘4’ in untreated check plots (UCP) this week, with a range between 0.5 and 4 across various treatments.

    Numbers of thrips are not as high as last year, but the recent cold weather made for a slow-growing crop. Cotton just stood there and sustained injury during the most susceptible stages (1 to 3 leaves).

    There is more variability in treatments this year, and I hope to summarize some of the data soon.

    It looks like the seed treatments were definitely weaker than products put in the furrow with the seed, but they were still much better than nothing (UTC).

    A Burndown Lesson

    Plots treated with aldicarb (AgLogic) continue to look the best right now (4 leaf stage).

    I learned a valuable lesson this year about timing of burndown herbicides and planting. We tried to make it work too close together and paid the price for it with untreated seed in a foliar spray trial for thrips.

    I was able to rate plots for thrips injury early on, but false chinch bugs (FCB), along with thrips, eventually killed plants in the untreated plots (no at-plant insecticide).

    More on Cotton


    Plots in a trial adjacent to this test that had at-plant treatments for thrips did just fine against FCB. So, be aware that if your at-plant treatment doesn’t go out, and you burn down close to planting, you are at serious risk for insect injury.

    Grasshoppers are still an issue. I saw a ton of immatures jumping around from plant to plant this morning (5/22). Use a high grasshopper rate of acephate (Orthene) for adults and the insect growth regulator (IGR) Dimilin (2 fl oz/acre) to keep nymphs from becoming adults. This IGR is great for grasshoppers.

    Soybean Insects – Similar Trends

    Not a lot of insect activity is turning up in soybeans, other than grasshoppers in some locations. If grasshoppers continue to be an issue in spots in cotton or soybean, consider using Dimilin at 2 fl oz/acre to control the immatures and break the life cycle.

    For controlling grasshopper adults, we recommend acephate (Orthene) for adult grasshoppers in cotton, so you can also control tobacco thrips. But in soybeans, use a high rate of a pyrethroid for some suppression of the adults, which are difficult to control. Go with Dimilin at 2 fl oz/acre for the immatures.




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