J. Terry Pitts, Oklahoma State University Extension Insect Pest Management (IPM) specialist at Altus, Okla., says cotton farmers should be aware of thrips infestations moving from wheat fields.
"Wheat has matured and thrips that lived on wheat have found a new home as cotton has emerged. Thrips normally infest seedling cotton and cause damage which results in slow growth and disfigured leaves.
"Today, many growers use in-furrow granules such as Temik or seed treatments of Gaucho Grande or Cruiser at planting. Manufacturers suggest protection can last up to more than 45 days after planting with Temik and up to 27 days after emergence with seed treatments. Damage can be described as leaves with bubbling, reduced growth that looks like a 'mouse ear', silver leaf as well as dead terminals. In addition, some describe damage on a numerical scale from 1 to 5 with one being the best and five a dead plant.
"If you are experiencing thrips damage greater than 3 to 4, you should apply an approved insecticide to avoid further damage and delay in growth. Some of the products approved as a thrips foliar spray are Bidrin, Cygon (Dimethioate), Centric, Orthene and Phaser. Also, similar chemistry should not be used as a seed treatment and an above ground spray. This would include Gaucho Grande, Cruiser, Aeris or Avicta as seed treatments and Centric as a foliar spray.
"Once cotton reaches the 4 to 5-leaf stage it is generally safe from thrips damage. Normally, the cotton plant has enough vigor and energy to grow away from any thrips feeding at this time. Once this growth stage is reached, thrips can be considered as beneficial as they will feed on mite eggs that can be present in cotton. For those interested in the thrips life cycle in the spring, it is normally 16 to 17 days. This allows for extremely high numbers migrating from wheat to cotton.
"If you have difficulty in controlling thrips, they are probably western flower thrips, which are more tolerant of insecticides than other thrips species. In an Oklahoma survey conducted by Dr. Miles Karner and Jerry Goodson in the early 1990s they found our populations are 91 percent western flower thrips.
"This could be the reason some growers experience heavy thrips damage after using an in-furrow or seed treatment product. If this occurs, it is best to apply one of the foliar products previously listed to avoid any delay in growth."
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