Entomologist Series With Jack Bacheler: North Carolina Cotton

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Cotton producers in the upper Southeast must manage approximately four to six different species of thrips in addition to the common tobacco thrips. Thrips levels and their damage are impacted by unpredictable weather patterns. Even though most species are managed similarly, western flower thrips can present challenging control issues in some years. Jack Bacheler, North Carolina State University Department Extension Leader, explained how to best manage thrips on cotton during a recent interview. JackBachelor.png

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Question: What are the major early-season pests to be aware of and how would you recommend controlling them?

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JB: We basically just have one - the thrips complex – that consists primarily of tobacco thrips, but also four to six other species. On occasion, we will get western flower thrips and those can be difficult to control, especially with foliar insecticides. Western flower thrips thrive in hot, dry conditions during early seedling growth. Fortunately they’re not a consistent problem for North Carolina producers. As a general approach to controlling this pest, essentially all growers use treated seed and most will have to come back with a foliar application approximately three weeks after planting or at the first true leaf stage, whichever comes first.

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Question: Why are thrips such a problem in North Carolina?

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JB: Because cotton is a tropical plant, it grows slower in cooler environments [than in most of Texas or the Mid-South, for example] leaving the plant in a thrips-susceptible stage longer. This longer period of vulnerability often results in increased thrips damage. Also, in the upper Southeast, we have a large amount of thrips host plant vegetation and generally smaller cotton field size, so our thrips levels are also higher than in most other areas of the Cotton Belt.

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Question: What are the late-season pests to be aware of and how would you recommend controlling them?

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JB: We plant almost all traited cotton varieties including Bollgard II (see Genuity® Bollgard® II) varieties so we don’t get a lot of caterpillar damage. Over the past 6 years, we have averaged approximately 0.15% late season boll damage from caterpillars (mostly bollworm) in grower managed Bollgard II fields, based on surveys of grower-managed cotton fields. Stinkbugs are far and away our biggest late-season insect problem, although 2-spotted spider mites are sometimes a headache, especially under hot, dry conditions. Unfortunately, relatively few stinkbugs can cause a lot of damage. Stinkbug build-ups are worse in years of plentiful rainfall. Under hot, dry conditions, wild and cultivated host plants don’t generate as many earlier stink bugs that in turn results in lower levels on cotton. Growers need to be examining quarter-sized bolls (approximately 1-inch in diameter), looking for stained lint or inner boll wall surface warts, and using the 10% internal boll damage threshold during weeks three to five of the bloom period, typically a time of high boll susceptibility to stink bug damage.

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In addition to controlling thrips, the base fungicides and the nematicide on some seed treatments also encourage early emergence and help control early seedling diseases and nematodes. With a proper plan, growers could achieve maximum yield potential by protecting against harmful insects. For more information regarding thrips control, click here.

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