Entomologist Series With Phillip Roberts: Georgia Cotton

10; ​In addition to thrips, Georgia cotton producers must be aware of stink bugs, specifically two different species: brown and southern green stink bugs. Controlling the two species may require a slightly different insect management plan. Phillip Roberts, University of Georgia Extension Entomologist​, explained what to look for and how to manage these pests during a recent interview. 

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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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PR: Our most common early season pest is thrips and they are very predictable and consistent. Wherever cotton is planted in Georgia, there are thrips. We encourage growers to use a preventative treatment at planting, which are primarily going to be one of the neonicotinoids seed treatments.
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Question: Are there any cultural practices that can impact thrips infestations? 
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 PR: Planting date and tillage practice are two cultural practices that impact thrips infestations. Cotton planted in April through the first 10 days of May typically have much higher thrips populations than later planted cotton. Also, utilizing a conventional tillage system with no residue left on the surface will have much higher thrips infestations than those fields where conservational tillage methods were used. 
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Question: When should growers be looking for thrips and what are some of the warning signs? 
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PR: Thrips infest cotton the day it comes up. Hopefully, we’ll get control with the seed treatment used at planting. The seed treatments will be active on thrips for about three weeks. If we have a heavy pressure of thrips, we may have to supplement the seed treatment with a foliar spray. When growers are looking for thrips, we have thresholds established. Our threshold is two to three thrips per plant with immatures present. The presence of immature thrips suggests that our at-planting treatment is not providing control. The eggs were laid on the plant, hatched and immature thrips are surviving and developing so that is an important part of our threshold. Thrips feed on the under side of the cotyledons initially, but will then move to the terminal bud to feed. If true leaves are injured, they will be misshapen or crinkled. They won’t develop normally. We always encourage farmers to look at the small, newly expanded leaves for thrips injury. Monitor for thrips damage until the fourth true leaf. Once you get to the fourth true leaf and plants are growing rapidly, thrips are rarely a problem.
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Question:  What are the major late-season pests to be aware of and how would you recommend controlling them? 
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PR: Primary late-season pests will be stink bugs. The populations can vary. We really try to make sure our growers are monitoring for damage and treating when thresholds are exceeded. Once we get to bloom, we need to be thinking about stink bug management. Prior to bloom it is rare they are a problem, however when plants begin to set bolls we need to intensify our search for stink bugs and damage. Scout and treat on an as needed basis until the last harvestable boll is 25 days of age. We’re pretty much relatively safe from stink bugs after that.
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Question: What should growers be looking for when scouting for stink bug damage? 
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PR: Look for internal injury such as callous growth or warts on the inner surface of the boll wall. Our thresholds are based on the percentage of bolls of that size that have been fed upon by stink bugs. Be observant for stink bugs when walking fields, brown and southern green stink bugs. Which stink bugs are present could influence your insecticide selection. An organophosphate insecticide is a good option for both, however a pyrehtroid insecticide is also a good option for southern green stink bugs. 
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Question: What would happen in your area if growers chose NOT to use an insecticide seed treatment product? 
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PR: That would be a mistake. If we don’t use a preventive insecticide at planting, we will have to apply two to three foliar sprays in a timely manner, and we still won’t have acceptable control. We really want to avoid situations where we have to spray multiple times early in the season. We’d rather put something down at planting and minimize foliar sprays. It also aggravates other cotton insects such as cotton aphids and spider mites. 
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Thrips and stink bugs can greatly reduce yield potential if not treated in a timely manner. Seed treatment products can help protect yields by offering a broad-spectrum insect protection throughout the growing season. For more information on seed treatment product options, visit acceleronsts.com
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