Thrips may not attract attention the way more notorious cotton pests such as bollworms, budworms, boll weevils and armyworms do, but year in and year out, they gobble up profits at a more consistent rate.
“Farmers will make more money managing thrips than any other cotton pest,” says Jim Leser, Texas Extension entomologist at Lubbock.
Leser, addressing the fifth annual Southwest Crops Production Conference recently in Lubbock, said cotton farmers face some factors they can't control, weather for instance. “But we can control pests. And Western flower thrips is a good target to aim for.”
Leser said farmers could save yield with timely pesticide applications for heavy infestations of beet armyworm, bollworms, etc. But those pests may cause damage as rarely as one in ten years. “Thrips control pays off every year>”
Although tobacco thrips may occur occasionally, the Western flower thrips is most common in the High Plains. “Damage may be substantial and can result in significant yield losses,” he said. “Potential for loss is enough to justify treatment.”
Leser said during cold, windy, sand-blown spring days in the High Plains, thrips make their way into the terminal bud of young cotton plants. “That's where they cause yield loss. They are not feeding on leaves but on the first squares.”
Age of the cotton dictates how many thrips a grower can tolerate. Just one from the cotyledon to the first true leaf stage is enough to justify treatment. At the two true-leaf stage, treat for two thrips. The progression holds through the five true-leaf stage, when five thrips would justify a pesticide application.
Leser recommends a bit of prevention with in-furrow or seed treatments. In field trials last summer, he found Temik in-furrow and Cruiser seed treatment to be the best options.
“Gaucho was not as effective on western flower thrips,” he said, “although all treatments, including foliar Orthene, resulted in reduced thrips populations and were better than the untreated check.”
A key, he said, is to kill thrips quickly enough to prevent reproduction. He said foliar products last about five days.
“Thrips can persist for a long time.”
Repeat applications will be necessary. He said Cruiser and Temik protect young cotton for about four weeks. Follow-up with foliar applications may be necessary.
He said Temik at 5 pounds per acre pushes near “nematode control levels. We don't need to spend that much to control thrips. We recommend 3 to 3.5 pounds per acre. That rate provides more consistent control than 2 to 2.5 pounds, although all rates produce a similar yield response. We can't separate the lower rate from the higher one by yield.”
Leser likes a preventive treatment for thrips, especially on irrigated cotton, and Temik or Cruiser seed treatment are his top choices.
“With Temik, 3 to 3.5 pounds per acre, follow with a foliar application, as needed and based on plant pathology and the number of immature pests. If enough immature thrips exist to trigger a foliar application, the foliar alone will be effective if timed properly. That would be my second choice.”
For those more visible but less frequent pests, Leser cited a number of control options.
Pyrethroids and Bollgard II are best for bollworm control. Bollgard II, Tracer, Bollgard and Steward are good on budworms. He recommends Denim, Steward and Intrepid, which he cites as the best of the three, for beet armyworms. Bollgard II is also good.”
He said Larvin is better than pyrethroids on bollworms.
Leser said Bollgard cotton is usually adequate for bollworms, except in heavy infestations. “It's not good enough to control heavy beet armyworm infestations but Bollgard II will be significantly better.”
He said Bollgard varieties may result in less aphid pressure. “Pyrethroid applications can trigger aphid populations.”
Leser said Intruder appears to be the best new product for cotton aphids. “Centric also looks good.” Furadan comes in third.
“We have a Section 18 for Furadan for 2003,” he said, “but use will be allowed only if Intruder and Centric do not provide adequate control.”