Early Season Thrips Control in Cotton

Thrips Damage to Young Cotton PlantsThere have been some unusually warm temperatures early this spring. These mild conditions are maturing spring host plants and flushing thrips into cotton earlier than normal. Thrips maintain high populations in early-planted cotton in many Southeastern regions.

 

 

Thrips Identification

Adults - slender spindle-shaped bodies with elongat​ed wings, less than 1/12-inch in length and can vary in color. Immatures - lighter in color, similar in shape, but lack wings, a magnification lens may be needed to see small immatures.

 

​Scouting for Thrips

Examine terminals and any newly expanded leaves, especially cotyledon up to the second true leaf stage.

Look for:
  • Adults and immatures1
  • Crinkled leaves
  • Silvery areas of the expanding leaf tissue
  • Darkened bud tissue
  • Death of terminal bud resulting in stunting

(As the plants grow, the older damaged leaves will remain crinkled, which may not be an indicator of current infestation)

Control/Threshold Levels

For 2012, the best control approach is a cotton seed treatment followed by foliar spray. A good seed treatment can be counted on to help in thrips management for up to 3 weeks. However, thrips can severely damage cotton for up to six weeks after emergence, so follow up treatments are necessary when seed treatments are no longer active in the plant. If no seed treatment insecticides were used, foliar insecticides will be needed for in-season control. Foliar insecticides may only be effective for a few days, potentially requiring multiple applications. Cotton producers should scout for thrips from emergence through the five-leaf stage.

​Early-Planted Cotton

When thrips infestations are high and cotton is planted early (prior to May 10) it is recommended that a foliar systemic insecticide should be applied at the 1-leaf stage when a commercial seed treatment was used2. Recent data on thrips insecticide application timing indicates that treatments applied at 1-leaf stage provided the most control3, 4. Any insecticide applications for thrips control applied at or after four- or five-leaf stage will be revenge spraying, providing little return on investment of application cost and time3.​

Late Planted Cotton/Reduced Tillage

For fields planted after May 10 or in fields with reduced tillage, the risk of high thrips infestation is lower and foliar insecticides should be applied when thresholds are met. Later planted fields should still be scouted and treated according to injury symptoms and the presence of thrips, particularly immatures, at or exceeding threshold (2 per plant)3. Planting cotton in mid-May puts a grower “on the fence” when deciding if thrips should be treated or not – scout and treat those fields as needed3.

Threshold

A systemic foliar insecticide should be applied when two to three thrips per plant are counted and immatures are present. Finding several immatures on a plant indicates that the at-plant insecticide is no longer active. For more information on insecticides and threshold levels for thrips refer to the University of Georgia Cooperative Extension Service Cotton Insect Management or your state university extension.​​