By Sebe Brown, Dr. David Kerns, Dr. Rogers Leonard – LSU AgCenter Entomologists
Thrips are annual pests of cotton in Louisiana. Damage by these insects cause stunted growth, delayed plant maturity and plant death under heavy infestations. Cotton is most susceptible to thrips from emergence to the 4 true leaf stage. Once cotton has reached the 4 true leaf stage, root differentiation has increased, terminal bud growth is accelerated and plants become less susceptible to injury.
The most common thrips found in Louisiana cotton are tobacco thrips, eastern flower thrips, onion thrips and western flower thrips. These insects overwinter on a variety of weed hosts. Planting seasons with windy conditions can have considerable influence on the severity of thrips populations in early cotton. Thrips are typically weak flyers and wind helps to distribute infestations across fields.
Cotton seedlings that experience cool, wet soils develop very slowly and remain susceptible to thrips injury much longer than cotton planted in a warmer, more optimum, environment. This year has been very warm and wet with considerable alternate hosts around cotton fields to produce sources of thrips infestations. With the loss of Temik for the 2012 growing season, insecticide seed treatments (ISTs) and over-sprays will be critically important for controlling thrips on seedling cotton.
Cotton seed comes with a variety of seed treatment options that may either be purchased through a seed company or applied by a dealer downstream. Outlined below are a few of my thoughts with regards to insecticide seed treatment packages on cotton seed.
Dow’s Phytogen seed comes with a base package of thiamethoxam (Cruiser), with Avicta Complete Cotton available upon request. Avicta Complete Cotton includes Cruiser for the IST, multiple fungicides and abamectin for nematode control. Information on Phytogen seed treatment options can be found here.
Monsanto’s Deltapine cotton seed comes with a combination of products that fall within the Acceleron treatment umbrella. The base package in cotton includes imidacloprid (Gaucho) and several fungicides. However there are several options within the Accereleron brand. Be sure that your seed is treated with what was ordered. These options are upgrades to Avicta Duo Cotton with Cruiser for insect control, several fungicides for disease control and abamectin for nematodes. Beware: the Acceleron seed treatment label in other crops may contain other products. More information on Acceleron seed treatment options can be found here.
Bayer’s Stoneville/Fibermax cotton seed comes with a base package that includes Gaucho for insect control and thiodicarb for nematodes that falls under the Aeris treatment umbrella. Producers also have the option to upgrade to Poncho/Votivo with clothianidin (Poncho) for insects and Bacillus firmus (Votivo) for nematodes. More information on Aeris seed treatment options can be found here.
Another option is to buy the minimum insecticide treatment available, and have a dealer apply additional insecticides downstream after the seed is purchased.
IST’s offer limited early season protection from thrips. Effective residual efficacy usually offers 10-14 days of control after plants emerge. Unsatisfactory residual control can occur with these treatments and cotton should be frequently scouted for thrips until the four leaf stage and when cotton plants are actively growing.
During 2011, western flower thrips were a problem in many Louisiana cotton fields. Western flower thrips can be difficult to control with standard applications of acephate, dimethoate, bidrin, etc. Producers also risk flaring spider mites and cotton aphids with repeated applications of broad-spectrum insecticides. Recent research conducted by the LSU AgCenter demonstrated satisfactory control of a complex of species including western flower thrips with Tracer and Radiant at 2 and 7 days after treatment.
The use of a nonionic surfactant with these insecticides can help increase efficacy against thrips. Rescue applications of foliar insecticides should be applied early in cotton development with applications at the 1-2 true leaf stage yielding significantly greater lint per acre than treatments applied at the 3-4 true leaf stage. Do not wait for thrips treatment in an attempt to time an overtop herbicide application.
Insecticide seed treatment options get producers off to a good start when it comes to insect pest management in cotton. However, these treatments should not be relied upon for sole control of all early season pests. IST’s are one of the best management practices (BMP’s) recommended by the LSU AgCenter for cotton IPM.
For more information concerning insect pest management, contact your local LSU AgCenter parish agent, LSU AgCenter specialist, or Louisiana independent agricultural consultant.