1. Introduction Cotton producers throughout Tennessee must battle glyphosate-resistant (GR) weeds. The most problematic of these is Palmer amaranth, also known as Palmer pigweed. One of the UT weed control recommendations for producers with glyphosate susceptible Palmer pigweed is a tank mix of glyphosate and s-metolachlor (Sequence®). In situations where GR weeds are present, growers have been using alternative methods to control Palmer pigweed. One method that has been adopted with success is a broadcast application of Ignite® (glufosinate) to WideStrike® cotton varieties. WideStrike® cotton varieties have tolerance to Ignite® and were planted on 65% of Tennessee cotton acres in 2010. Ignite® is efficacious in controlling GR weeds, including Palmer pigweed. Tennessee cotton producers are interested in the possibility of tank mixing insecticides with an Ignite® application. Applications of Ignite® on WideStrike® cotton can cause crop injury though rarely, to date, has this injury caused yield loss. The effect of insecticides tank mixed with Ignite® is unknown. Conclusions These data would suggest that maturity can be delayed and yield decreased by an early season Ignite® or Ignite® + insecticide application to WideStrike® cotton that is already stressed by thrips. Cotton producers must weigh this risk against potential yield loss from GR weeds. Evaluation of WideStrike® Cotton Injury from Early Season Herbicide x Insecticide Tank Mixes in 2010 Evaluation of WideStrike® Cotton Injury from Early Season Herbicide x Insecticide Tank Mixes in 2010 Sandy Steckel, Scott Stewart and Kyle Pearson. The University of Tennessee, West Tennessee Research and Education Center, Jackson, TN Objective The objective of this research was to evaluate the tolerance of PHY 375 WRF (WideStrike®) cotton to Ignite® or Sequence® alone or when tank mixed with various insecticides in the presence of thrips. Ignite® Based System in cotton left and glyphosate based system in soybeans right Materials & Methods Planted: May 14, No-Till, 38-inch rows Variety: Phytogen 375 WRF, no insecticide seed treatment Design: Four replications in a Factorial design (Herbicide x Insecticide) Plots: 4 rows X 30 feet Foliar treatments applied on June 1 to two-leaf cotton (Note: There was significant thrips injury to plants at the time of treatment application) Evaluation of Visual Crop Injury: June 3 using a 0 – 100 scale, 0 = no injury, 100 = plant death Thrips collected from 5 plants/plot on June 3 & 7 Harvested Sept 16 & Oct 1, two center rows Results Ignite® caused more visual injury compared with Sequence® (data not shown). Dimethoate caused more visual injury compared with the other insecticides (data now shown). All insecticide treatments reduced immature thrips numbers and injury (data not shown). Ignite® reduced square counts compared with Sequence® (data not shown) and also delayed maturity as evidenced by first and second pick data. Ignite® decreased seedcotton yield compared with Sequence®. (P = 0.0007) Factor Analysis for Total Seedcotton TreatmentMean Herbicide (H) Sequence®4733 P = 0.0007 LSD = 299 Ignite®4160 Insecticide (I) Untreated4648 P = 0.1969 LSD = 423 Dimethoate4230 Bidrin®4361 Acephate4549 H x I InteractionNS P = 0.7009 LSD = 598 First Harvest (top) and Second Harvest (bottom) lbs seed cotton/A Total seed cotton lbs/A Ignite 29 + Acephate 4 The authors wish to express their appreciation to Cotton Incorporated for support.