The most important thing to remember about cotton thrips is getting seedling cotton plants to grow through their thrips-susceptible window, which is about the first through fifth true leaf. Choosing the right strategy and products can get young cotton through it.
“You want your plants to move through that window as fast as possible. Anything you can do to make your plants grow faster will minimize the thrips problem. They cause fewer problems on rapidly growing plants,” said Ron Smith, Auburn University Extension entomologist.
Seed treatments are valuable, he says. “You can’t live without them, but they don’t always hold thrips injury below the threshold level. We’ve got Gaucho, which is imidacloprid, and Cruiser, which is thimethoxan.
Certain weather conditions sometimes will favor one of those over the other. For example, Cruiser is a little bit more water-soluble than Gaucho. So Cruiser will perform better in a dry spring while Gaucho will perform better in a wet spring like last year.”
Acetate, including Orthene and the generics, at 1 pound in-furrow is not nearly as effective as a seed treatment and sometimes not much more effective than an untreated seed alone, says Smith.
“We have imidacloprid in a liquid, which is Admire Pro and is applied in-furrow. It can be as effective as a seed treatment, but the application method appears to be a critical limiting factor. It definitely wasn’t as good as a seed treatment. Most of us were putting it out with a flat-fan nozzle sprayed right in the furrow, and it didn’t help at all. It looked good with folks who did it with a .55 orifice nozzle pointed directly down with low pressure right above the furrow. It was equal to the seed treatments.”
Foliar sprays are needed on top of seed treatments when cotton is not growing rapidly, says Smith. “We’re now recommending that cotton planted up to about May 10 should get an automatic spray on top of the seed treatment at the first true-leaf stage.”
The "Cadillac" of cotton foliar sprays
There are a number of options available as far as foliar sprays, he says. “The Cadillac product in my opinion as far as being effective throughout the entire production season is Orthene or a generic acetate material. At 3 to 6 ounces per acre, nothing is better. Radiant, at 1 ½ to 3 ounces is also very effective. It’ll cost a little more, but its particular advantage is that it doesn’t flare spider mites like acetate or Orthene.”
Looking ahead, there are a few issues on the horizon that growers need to be aware of, says Smith. “Thrips are now showing resistance to Cruiser seed treatments in Louisiana, Mississippi, Arkansas and Tennessee. Also, the neonicotinoids class of chemistry – which includes our seed treatments – has been associated with the bee kill controversy. We need to be giving some thought as to what we might do if we lost resistance, or if EPA removed it from the market a few years down the road.
“That’s really all we have as far as thrips control now. Our granular insecticides like Temik are gone and no one knows how long Thimet will be on the market. So we could be in a shaky position down the road regarding thrips control on cotton.”