Despite their small size, thrips are a consistent pest of seedling cotton. Tobacco thrips are the most common species observed in Tennessee, but several other species may also occur. Winged adults migrate into fields when seedlings emerge. Adult and immature stages feed by puncturing leaf cells and emptying their contents. Injury causes foliar deformity (leaves crinkle and cup upward), stunting, delays in maturity, and may cause stand loss. Preventative in-furrow insecticides or seed treatments are recommended. A foliar treatment may also be needed in some cases. Tobacco thrips have recently developed resistance to some neonicotinoid insecticides such as thiamethoxam (i.e., Cruiser).
The presence of deformed, crinkled leaves and a silvery color is often a sign of thrips infestations. Scouts should visually assess the level of injury on emerging leaves. Numbers of thrips can be sampled by vigorously shaking/thumping seedling plants over a white-surfaced container (e.g., cigar box or Cool Whip container). A 5-10 X hand lens is suggested to help distinguish adult and immature stages.
In-furrow insecticides or seed treatments are recommended. Treatment is recommended prior to the third leaf stage when an average of 1 or more thrips are found per plant, especially when immature thrips are present and there are obvious signs of injury on newly emerged leaves.
|Insecticide (Trade Names) for THRIPS||Lb Active Ingredient per Acre||Amount Formulation per Acre||Performance Rating Thrips / WFT***|
|In-furrow Systemic Sprays:|
|acephate 90 (Orthene 90S)||0.9 - 1||1 - 1.1 lb||7 / 5|
|disulfoton (Di-Syston 8)||0.75 - 1||12 - 16 oz||6 / ?|
|imidacloprid (Admire Pro 4.6)||0.27 - 0.33||7.4 - 9.2 oz||8 / 2|
|imidacloprid (Velum Total 2.17)||0.24 - 0.31||14 - 18 oz||8 / 2|
|Foliar Sprays: *|
|acephate 90 (Orthene 90S)||0.18||3.2 oz||7 / 5|
|dicrotophos (Bidrin 8)||0.1 - 0.2||1.6 - 3.2 oz||8 / 5|
|dimethoate 4||0.125 - 0.25||4 - 8 oz||7 / 2|
|spinetoram (Radiant SC 1), suppression **||0.012 - 0.023||1.5 - 3 oz||8 / 7|
|imidacloprid (Gaucho 600, Aeris, Acceleron Standard, Acceleron Elite, Avicta Elite Cotton Plus)||0.34 - 0.375 mg active ingredient per seed||8 / 2|
|Orthene 97 ST or Acephate 80S *||Acephate can be applied to a seed at 6.4 oz/100 lb seed (Orthene 97 ST) or 8 oz/100 lb seed (Acephate 80 S)||5 / 3|
* Not recommended as a standalone treatment for thrips control.
** Radiant SC is suggested if western flower thrips are present in significant numbers. The use of an adjuvant is recommended when using Radiant SC for control of thrips.
*** General rating for typical thrips control vs. rating specific for western flower thrips (WFT).
- It is generally best to make any foliar insecticide applications by the second leaf stage. More than one foliar insecticide application is rarely justified.
- A preventative foliar application is often suggested under adverse growing conditions such as cool weather.