South Carolina Cotton: Bollworms, Stink Bugs Moving in from Corn

Trap with Bollworm - Corn Earworm - CEW moths. Photo: Gus Lorenz, Extension Entomologist, University of Arkansas, Division of Ag

We still have plenty of aphids, but there was a report this week of the aphid fungus in the middle of the state. So, if you haven’t treated for aphids and the crop looks like it is not suffering from the additional stress, you might be able to save some money on control of aphids.

Remember, though, that the fungus is not as predictable as it used to be. So if you clearly find stress, you might want to remove the aphids as a stressor. If you need another reason to spray for aphids, we are getting close to needing to be able to see bollworm eggs on leaves, and aphids make that almost impossible.

However, keep in mind that the neonicotinoids might or might not provide good control. See our handbook for a list of recommended products. Expect about 50% control of a neonic-tolerant population, at best. Do not apply Bidrin for aphids this time of year – right before we see bollworms.

Counts of bollworm moths in our pheromone traps have started to increase, so we are at the beginning of a flight out of corn.

You don’t want to kill all of your beneficials right before that. Scout for bollworm and stink bugs. Spider mites made some headway this week with the hot temps, reduced humidity and little rainfall.

Hopefully, the scattered storms will keep coming and washing away spider mites. For now, take a hand lens with you and check for mites under leaves. At least look for the stippling on upper surface of leaves, but know that you are a little late on noticing them at that point.

Reports of plant bug issues have declined, but continue to look for tarnished plant bug (TPB) using a drop cloth once flowering starts. Get a black drop cloth to help you see the tiny green nymphs. I will be giving away a few of these at the upcoming workshops.

Numbers of nymphs doubled from last week in my trials, although we are still well below the threshold (about 1 TPB adult or nymph every other row foot). That is the treshold used in Midsouth states where they routinely battle this pest.

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Finally, we will have a lot of brown stink bugs moving out of drying corn into cotton very soon.

From Around The State

Charles Davis, county agent covering Calhoun and Richland Counties, reported that “our biggest insect problem in cotton this week is high aphid populations in some fields. We have sprayed a few, but I just found out from consultant Drake Perrow that the aphid fungus is here in the Cameron area. Hopefully, the need for chemical control will soon be past. PGR applications are going out on the blooming cotton, but we have a lot of cotton just hitting 5 nodes.”

Mitch Binnarr, representative with Corteva Agriscience, reported that he is seeing many aphids and spider mites in the Pee Dee Region and that producers are looking at spraying. Here is a shot he took of some cotton leaves with typical stippling on the upper surfaces that indicate leaves are heavily colonized on the undersides with spider mites.

Tom Smith, a local consultant, reported that cotton growth varies from 6-10 true leaf to 3rd week of bloom. Aphids and spider mites still building, and bollworm moth and stink bug activity increasing, and treatments have started for bollworm and stink bugs on older cotton (late second to third week of bloom).

Fleming McMaster, a local consultant reported that he is seeing brown stink bugs in cotton and soybeans – not at treatment levels yet, but seeing them. He also has not observed the aphid fungus yet in his area of southern South Carolina.

Also, we had a report from a North Carolina-based consultant that crosses the line into South Carolina that he was picking up fields in the second field of bloom with greater than 40% stink bug damage in Marion County.

With these reports of stink bugs in some of the older cotton, we need to ensure we are using the boll-injury threshold and looking for stink bugs. Just good observation, as that used by Tom here, lets you know what you have. Use bifenthrin for hard-to-kill BSB.

Scouting Workshops

Your ag-focused county agents and I will be offering three in-field scouting workshops for cotton and soybean insects this summer. The interactive workshops will be held:

July 18 in Cameron (please RSVP with either Jonathan Croft croft@clemson.edu or Charles Davis cdvs@clemson.edu, so we can plan for lunch).

July 31 in Lake City(please RSVP with either Hannah Mikell hmikell@clemson.edu or 803-435-8429 or Jacob Stokes stokes3@clemson.edu, so we can plan for lunch).

August 7 at the Edisto REC near Blackville, (again, so we can plan for lunch, please RSVP with either me [greene4@clemson.edu], Mary Katherine Bamberg [mbamber@clemson.edu], Joe Varn jvarn@clemson.edu, or Marion Barnes jbrns@clemson.edu).


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