One thing that is almost guaranteed each year when cotton starts to emerge — thrips are coming.
“They are a very predictable, consistent pest in cotton,” says Dr. Phillip Roberts, an Extension entomologist with the University of Georgia Extension service in Tifton. “That’s why we want to use an at-planting treatment.
“Temik has been our standard for many years and then we have the seed treatments. But Temik is short right now.”
Thrips concentrate their feeding in the terminal bud, causing stunting and irregular growth.
Dr. David Kerns, an entomologist with the Texas AgriLife Extension Service in Lubbock is almost an echo of Roberts: “Thrips are our main problem early and Temik is the Cadillac treatment. But it’s going to be hard to come by for a lot of people. We know it’s short this year. So my recommendations would be to use one of the seed treatments. And there are two basic chemistries to choose from – imidacloprid and thiamethoxam.”
Imidacloprid insecticide is the active ingredient in Bayer CropScience’s Gaucho 600 on-seed treatment. It is also the insecticide component of Bayer’s Aeris on-seed treatment. Thiamethoxam is the insecticide ingredient in Syngenta’s Avicta Complete on-seed treatment.
With Bayer’s decision to begin phasing out production of Temik over the next few years, the Cotton Belt will eventually lose one of the very best insecticide/nematicides ever. But current availability of Temik has been hampered due to legal problems with a manufacturing plant in West Virginia that produces one of the components of Temik.
With that in mind, Roberts suggests using Temik frugally.
“Temik is a little more active compound in terms of controlling thrips,” he says. “Temik will give you a little more residual control when you compare it to seed treatments. So if you have a limited supply of Temik, you might want to use it in what I would term ‘high-risk’ areas.
“Historically, about 65% of our acres are still using Temik, which is different than in other parts of the country. In the Southeast, more Temik is used than in the Mid-South,” says Roberts. “Nematode control probably has something to do with that because we have problems with root-knot nematodes in our sandier soils.”
No matter if growers rely on an on-seed treatment, Temik, or both, it’s vitally important to protect plants from thrips from the time they emerge until they reach the 4- or 5-leaf stage. They say a cotton plant that gets behind early never catches up.
“Thrips can do quite a bit of damage, and it’s not uncommon to see as much as a 20% reduction in yield,” says Kerns. “It sets the crop back, and when you have a crop that is set back, it’s just hard for it to make up those heat units.”
In a perfect world, seedlings emerge and reach the 4- to 5-leaf stage quickly. But this is not a perfect world, and sometimes foliar sprays are the only alternatives in thrips control.
“If we spray, the threshold is two to three thrips per plant, and with immatures present,” says Roberts. “The key is the immatures, because when you have immatures present, that tells you that the at-planting insecticide is no longer active. That’s important.
“Some of the things I talk to growers about is just understanding the biology of thrips. One thing I stress is that we are going to have our heaviest pressure on our earliest-planted cotton. When a plant is not growing rapidly, whether it’s from cool temperatures or some other plant stress, that’s when thrips can really hurt you in terms of yield potential,” Roberts says.
Once it’s determined that thrip pressure is building, it’s essential that a grower knows exactly when to crack the whip.
“The first two weeks post-emergence is the most critical time for managing thrips,” Kerns says. “Be sure timely applications are made. You can’t wait because in just a couple of days, you can suffer pretty good damage. A lot of people want to time that with an application of Roundup. It doesn’t always work. You have to be Johnny-on-the-spot.”
If foliar applications are called for in Texas, Kerns recommends acephate. “It’s relatively inexpensive, and with 3 to 3½ ounces, you can get upwards of five days control,” he says.
If conditions call for foliar applications to control thrips in Georgia, Roberts recommends Orthene (acephate), Bidrin or dimethoate — all systemics that should carry the plants to the 4- or 5-leaf stage.