Efficacy of Seed Treatments in Relation to Early-Season Thrips Dynamics and Cotton Growing Conditions during a 6-Week Planting Window

Thrips injury to seedling cotton during the 1-4 true-leaf stage can cause stunting, delayed maturity, reduced yield and plant death.  Factors known to increase the risk of injury include weather conditions that delay cotton growth (i.e. increase the time that cotton is in the susceptible stage), environmental variables that influence efficacy of insecticides, and high thrips pressure that occurs when peak dispersal of adult thrips from overwintering hosts coincides with cotton in the susceptible stage.  All of these factors are variable among geographic locations and across the planting window at any given location.  Thiamethoxam and imidacloprid, applied as seed treatments became the primary chemistry for thrips management due to their systemic activity, ease of use, and reduced-risk status relative to previously used chemistries (i.e. aldicarb).  This study was conducted to examine the efficacy of three seed treatments during the cotton planting window in Prattville, AL.  Small plots were planted weekly from April 11 to May 16, 2016.  Measurements recorded from plots each week included plant height, number of true leaves, thrips injury ratings, dry weights 42 days after plant, and yield.  Early-season thrips population dynamics were monitored weekly from plating until cotton reached the 4 true-leaf stage using sticky traps to catch dispersing adults, and counting adults, larvae, and eggs on cotton seedlings.  Performance of Aeris®, Avicta® Duo and Avicta® Elite  will be presented along with thrips population dynamics and cotton growing conditions over this 6-week planting period.