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Predicting insect pest infestation is at best an educated guess and at worst no more than a fool’s errand.

Ron Smith, Editor

February 4, 2021

6 Min Read
cotton-seedlings-staff-dfp-0711.jpg
The usual suspects — thrips, plant bugs, and flea hoppers, with bollworms, stink bugs, whiteflies and spider mites are potential accomplices, depending on location.Staff

“Round up usual suspects.” That line from the classic movie Casablanca offers a good starting point for cotton farmers preparing for 2021 insect strategies.

Extension entomologists across the Cotton Belt say predicting insect pest infestation is at best an educated guess and at worst no more than a fool’s errand. They do name usual suspects — thrips, plant bugs, and flea hoppers, with bollworms, stink bugs, whiteflies and spider mites as potential accomplices, depending on location.

Weather might play a role, said David Kerns, Texas A&M AgriLife Extension entomologist, College Station.

“Weather drives everything,” Kerns said. “The long-range forecast predicts colder, drier conditions. For cotton, that could make thrips a little worse since cotton will not be growing as fast.

“For flea hoppers, who knows? A lot depends on how many weeds we have in pastures or roadsides. If those dry off quickly, we could get a big flush of flea hoppers but probably not very persistent. If those weeds continue to grow, we might see smaller numbers of flea

hoppers spread over a longer period. It’s hard to predict.”

He said corn acreage, especially in Central and South Texas, could mean more bollworm pressure. “We expect more corn acreage.”

Kerns doesn’t expect to see new insecticides this year. “FMC has some new mix products,” but no new chemistry. “A BASF cotton and sorghum label for Sefina could help with an aphid outbreak.”

Kerns and other entomologists say the new Bt trait, ThryvOn, with activity on thrips and plant bugs, will not be commercially released this year.

“We will see some demos,” Kerns said. “It’s really good on thrips, decent on plant bugs. I think it’s having an impact on flea hoppers; we can measure that on fruit retention but not population numbers. I’m not sure if it will reduce insecticide applications but it may make them look better.”

NORTH CAROLINA

“Our big cotton insect surprise in 2020 was tarnished plant bug (Lygus bug),” said North Carolina State Extension entomologist Dominic Reisig. “This pest has always been around but not at treatable levels. That changed around 10 years ago in northeastern North Carolina and has steadily blown up to treatable levels on many cotton acres. It’s been expanding steadily westward and south from northeastern North Carolina and southeastern Virginia. We were astonished to find it at treatable levels in the North Carolina Southern Coastal Plain and into the Piedmont.”

Shrinking cotton acreage is a factor.

“Tarnished plant bugs concentrate on remaining acres, but the expansion in 2020 was rapid compared to what we’ve seen in previous years.”

Reisig recommends producers hire a scout this year “to monitor fields weekly for square retention and bug numbers, from squaring through about two weeks after cutout. We’ve had trouble with pyrethroid resistance lately and it’s important that growers rotate insecticides.”

TENNESSEE

Scott Stewart, University of Tennessee Institute of Agriculture, expects nothing unusual. He expects some thrips and bollworm pressure, but “plant bugs are the No. 1 pest,” he said. “It’s been that way for years. How bad, that’s anybody’s guess.”

“Plant bugs pressure is holding pretty steady, as is how we manage

them. We have good thresholds. We don’t have a lot of chemistry but it’s good chemistry. Diamond, Orthene and Transform are the top three.”

He said ThryvOn is “great on thrips and pretty good on plant bugs but not an option for 2021. We will manage thrips the old-fashioned way  good seed treatment and foliar apps.”

He and other entomologists say some insecticides, including acephate or Orthene, “are not as effective as they used to be on thrips in some areas. We encourage folks to look at alternatives. We need more data on efficacy and economics. Those products are still providing some protection, just not as good as they were.”

ALABAMA

Ron Smith, who retired this year from Auburn University Extension after more than four decades, said Southeastern farmers will be looking at “three or four pests. Producers will need to manage thrips and plant bugs across much of the Cotton Belt.

“In the Coastal Plains, the stink bug is our most economically damaging pest most years,” he said. He recommends growers “fine tune management and react to silverleaf whiteflies. We don’t need to make big changes; we just need to keep fine tuning insect management. We are living in a low insect loss period over most of the Cotton Belt. We need to keep it that way.”

Smith said Alabama cotton had no disaster insects in 2020. “We need to stay on top and fine tune management every year; spray when we need to and don’t spray when we don’t.”

LOUISIANA

Sebe Brown, LSU AgCenter entomologist, Alexandria, said producers “can always count on thrips early season but also very late over the past couple of years. Louisiana recommends a full treatment (0.375 mg/ai seed) of imidacloprid plus overtreatment of acephate at 6.4 oz/cwt or an Aeris seed treatment, if that is an option.”

He said acephate alone has a short residual and will not protect seedlings

long enough without imidacloprid. “Seed overtreated with acephate cannot be returned.

“In-furrow, 0.75 to 1.0 lb Orthene is an option, as well as 9.2 oz/acre of a 4.0 lb/ai acre imidacloprid. Aglogic’s Aldicarb 15G is an excellent granular, in-furrow option that has replaced Temik. Rates are 3.5 to 4.0 lb/acre for thrips.” Brown said foliar rescue treatments are an option but using an acephate seed overtreatment or in-furrow options will save money, an extra trip and potentially unnecessary flaring of secondary pests from a foliar spray.

“It’s better to handle thrips in the ground than over the top, if possible.”

He said tarnished plant bugs were heavy in many fields last year, partly due to a mild winter and early host plant bloom in non-crop areas. “2021 appears to be setting up the same way with blooming plants already appearing in portions of Louisiana and no frigid temperatures forecasted.”

He said growers need to be cognizant of management decisions and alert for big TPB numbers. Also, consider nearby acreage. “Is a neighbor planting wall-to-wall corn next to my cotton? Will my budget allow more TPB sprays?”

Brown said spider mites were non-existent for much of Louisiana last year, likely because of ample rainfall and large use of pre- and post-glufosinate for resistant weed control. “Midsouth entomologists demonstrated that glufosinate has good activity on two-spotted spider mites. Growers get a two-for-one, weed control and mite control from one product in cotton. Growers may see mite benefits again this year if glufosinate is in their herbicide regime.”

Several entomologists mention bollworm resistance in the older Bt products (Cry1 and Cry2) and recommend producers begin switching to the three-gene trait or prepare to spray on the older products. Some recommend limiting use of the three-gene products in corn to limit resistance.

About the Author(s)

Ron Smith

Editor, Farm Progress

Ron Smith has spent more than 30 years covering Sunbelt agriculture. Ron began his career in agricultural journalism as an Experiment Station and Extension editor at Clemson University, where he earned a Masters Degree in English in 1975. He served as associate editor for Southeast Farm Press from 1978 through 1989. In 1990, Smith helped launch Southern Turf Management Magazine and served as editor. He also helped launch two other regional Turf and Landscape publications and launched and edited Florida Grove and Vegetable Management for the Farm Press Group. Within two years of launch, the turf magazines were well-respected, award-winning publications. Ron has received numerous awards for writing and photography in both agriculture and landscape journalism. He is past president of The Turf and Ornamental Communicators Association and was chosen as the first media representative to the University of Georgia College of Agriculture Advisory Board. He was named Communicator of the Year for the Metropolitan Atlanta Agricultural Communicators Association. Smith also worked in public relations, specializing in media relations for agricultural companies. Ron lives with his wife Pat in Denton, Texas. They have two grown children, Stacey and Nick, and two grandsons, Aaron and Hunter.

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