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Upper Southeast cotton growers brace for thrips invasion

• The major variable on how much damage thrips cause is largely dependent on the weather and the size and timing of thrips flights into cotton fields.• In terms of yield differential, Herbert says over the past 10 years thrips-related yield loss in Virginia has averaged about 380 pounds of lint per acre.• In North Carolina, average losses are about half that amount.

Roy Roberson 2

April 25, 2012

6 Min Read
<p> <em><strong>NORTH CAROLINA State University Entomologist Jack Bacheler discusses thrips management.</strong></em></p>

A warm winter, an exceptionally warm March, heavy and early thrips flights — all the elements seem to be coming together for the perfect storm of damage to cotton for 2012.

North Carolina and Virginia have a well-earned reputation as being ‘thrips central.’ Even under the best of weather conditions, thrips can be a handful to manage. All early indications are that 2012 won’t be among the best set of weather variable growers have had to face in recent years — at least not in terms of managing thrips.

Virginia Tech Entomologist Ames Herbert says his years of data indicate the difference in controlling thrips versus no control ranges from $400 to $700 an acre in cotton. The major variable on how much damage thrips cause is largely dependent on the weather and the size and timing of thrips flights into cotton fields.

In terms of yield differential, Herbert says over the past 10 years thrips-related yield loss in Virginia has averaged about 380 pounds of lint per acre.

In North Carolina, average losses are about half that amount.

Cotton prices have stabilized in recent months, but continued good prices mean these little pests can cost big dollars.

Add to the seeming perfect storm for thrips, a two week or more head start on planting all crops in the Upper Southeast, and the potential for thrips damage is significantly greater than in what are usually called ‘normal’ years.

Aldicarb, sold under the tradename Temik has been a proven thrips killer since its introduction to the marketplace more than 30 years ago. Last year growers had to fight thrips without their primary weapon, and it appears they will have to do t again in 2012.

Temik manufacture was halted in 2010 and only a small supply was left for 2011 and only what remains in storage houses will be available in 2012.

New product not available

A new aldicarb product (Meymik), which is nearly identical to Temik, has been cleared for use by the EPA, but will not be available to farmers for the 2012 thrips season.

Reportedly, work is well under way on a new production facility for Meymik production in Georgia. However, under the best of scenarios, the new Temik-like product won’t be available to growers until the 2013 season for cotton.

North Carolina State Entomologist and thrips fighter Jack Bacheler says there is still lots to learn from Memik, even when it gets to the market place.

“It is supposed to be very similar to Temik, but little is known about the possible costs, flowability and efficacy of Meymik. Additionally, the successful re-registration of aldicarb (a carbamate), the active ingredient, by the EPA in 2014 or 2015 season is not a given,” Bacheler points out.

Seed treatments are a must for starters, but alone these products have not proven to be adequate to manage thrips in most years. 

The good news may be that all the nicotinoid seed treatments, with or without additional insecticide and nematode combinations in the seed treatment, essentially work the same.

The bad news is the same as the good news. Growers will likely get what they pay for with these seed treatments, but years of research in North Carolina and Virginia indicate they are not enough to manage heavy infestations of thrips.

With Temik, growers got the added benefit of managing nematodes. Nematode damage often mimics thrips damage and vice-versa. Seed treatments with nematicides have not been adequate in fields with heavy nematode pressure.

“The Holy Grail of seed treatments would be a high rate (or new active ingredient) of an insecticide on cotton seed that would remain active for 4-5 weeks. In many cases, the 3 weeks of seed treatment activity from current seed treatments seems to come up short by only a week or two.

So far, with the exception of a few testimonies to the contrary, this seemingly simple answer to short-lived seed treatment activity has defied the best efforts of major seed companies, consultants and university scientists,” Bacheler says.

He adds that foliar insecticides following seed treatments remain an important component of the thrips arsenal for North Carolina and Virginia growers. “We and others have confirmed that the combination of Orthene following a seed treatment greatly increases the odds of having to treat later for cotton aphids and spider mites,” Bacheler cautions.

Expensive materials

Radiant and Benevia will likely be significantly less disruptive against beneficial insects that help manage aphids and mites. The major downside of these materials is their prohibitive $20-30 per acre costs at the rates tested.

“This year’s series of tests in Virginia and North Carolina will evaluate the effectiveness of several rates of these insecticides in the hope that one or both may give us an additional tool in minimizing our annual thrips dilemma,” Bacheler says.

Herbert and Bacheler have a long history of battling thrips and a well-deserved reputation as ‘thrips killers.’ Both contend thrips, even high populations on early planted cotton can be managed, but not without a lot of scouting and timely applications of pesticides.

Among the tools to be tested in 2012 are several high rate options of several materials that are currently labeled for use on cotton.

Another option will be the presence of multiple insecticides and nematicides on the same seed. One example for 2012 will be the Aeris/Poncho/VOTiVO option containing two nicotinoids and a conventional and biological nematicide. 

Bacheler and Herbert tested several new in-furrow sprays for thrips control in 2011. Research findings were varied, but preliminary results, based on one-year of data, indicated Admire Pro (an imidacloprid) provided the extended five-week control researchers are seeking.

Research at Wilson, N.C., and at the Tidewater Agriculture Research and Extension Center in Suffolk, Va., showed good results using this material in the furrow.

Despite an impressive arsenal of thrips killing tools and years of experience managing these tiny yield-busting critters, growers are still faced with exactly what to do to prevent damage.

For the 2012 growing season, Bacheler says growers should use Temik, if they can find any, on early planted cotton.

Temik is still legal to use, but only carryover supplies from the 2010 season are available, though some growers stored a supply once they learned it would be taken off the market.

The second thing growers should do this year, the North Carolina State entomologist says, is to try to base follow-up foliar sprays behind seed treatments, based on terminal damage assessment and to plant a portion of total acreage between May 15 and May 25 to shorten the thrips susceptibility window.

Though early indications are for heavier than usual thrips populations this year, weather changes can have a huge effect on moth flights and subsequently thrips pressure. However, even in ‘good’ thrips years, the heart of Virginia-Carolina cotton country is likely to live up to its reputation as Thrips Central.

(For additional comments from Jack Bacheler on thrips control in North Carolina and Virginia, see http://southeastfarmpress.com/cotton/thrips-big-start-virginia-north-carolina).

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