South Carolina Cotton: Still Making Thrips Decisions

Thrip damaged cotton. Photo: Andrew Sawyer, University of Georgia

Drake Perrow, consultant in Calhoun County, reported on Wednesday that he observed spider mites on pinhead square cotton that had 4 pounds of aldicarb per acre applied at planting and no acephate oversprays. So if spider mites are going to show up after aldicarb, they can show up under any circumstances, as aldicarb usually has some suppression of spider mites.

Jonathan Croft, county agent in Orangeburg County, reported that several groers this week said that grasshoppers seemed to the big insect problem in some fields last week.

Mitch Binnarr with Phytogen Seed reported that much of the cotton he and his growers are tending is sustaining heavy injury from thrips. He mentioned that it was anywhere from 1- to 6-leaf cotton and he was wondering what our stance is on treating for thrips after the cotton has 5 leaves on it.

Historically, sprays for thrips on seedling cotton with more than 5 true leaves are not justified if plants are growing normally. However, we have a couple of things going this season that will likely make it better to treat after 5 leaves.

  • First, “historically” doesn’t cover all years. There are exceptions, and this year might be one. This is one of the hottest and driest Mays I remember in South Carolina
  • Second, “growing normally” does not apply to cotton seedlings that have been experiencing extreme heat and drought. The plants are simply not growing as they would be with adequate moisture.

And because all of the at-plant insecticides require moisture to activate and move them into the plant, they are not performing as they normally would. That allows more injury than normal.

The recent rains have dramatically knocked down thrips populations in my plots in Blackville. Populations were heavy before the rains started. I doubt if they will return to those heavy levels, and much of the crop will rapidly grow out of light to moderate levels of injury.

Many of the cotton seedlings with heavy injury will also likely grow out of the injury, but they will be delayed. With the rain likely continuing for the next several days, I would limit any foliar sprays for thrips, unless they are absolutely necessary, and you can find a window of a few rainless hours after you pull out of the field.

Meanwhile, In Soybeans

Deer continue to be a problem, and we have found that the soap-based products, such as formulated insecticidal soap (Hinder, etc.) continue to be good repellents.

AgFax Weed Solutions


Insects have not been a widespread issue yet in soybeans, but we are seeing grasshoppers and threecornered alfalfa hopper (TCAH) as the most numerous insects in our sampling so far.

Pyrethroid insecticides are the best choices for these pests. Remember, though, that it takes a high rate to kill the large adult grasshoppers, and you will likely miss some of them. We simply cannot put enough active ingredient into the large bodied grasshoppers.

Treat for grasshoppers when the stand is threatened early or when defoliation levels exceed 30% before mid-bloom and 15% after mid-. Treat for TCAH at 3 per row-foot or more than several per sweep. Also, we have detected some stink bugs already in soybeans, so it could be a big stink bug year.


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