Interaction of cotton insecticide seed treatments and early season herbicides

Thrips are one of the most important pest species in the early growing season of cotton in the Mid-south portion of the United States cotton belt. In most years it is not uncommon to over spray 20-30% of cotton acres for thrips.  However, within the last two years, thrips pressure has increased.  In 2011 and 2012 more than 70% of cotton acreage was over sprayed for thrips control, independent of insecticide seed treatments.  In this early development stage of cotton, the first application of an herbicide system is also being applied. Interaction of early season herbicides with insecticide seed treatments may alter the efficacy of either product, or may have an impact on cotton plant development. The objective of this research study was to examine efficacy changes between various seed treatments after the application of pre and post emerge herbicides.  One trial was designed using the combination of three insecticide seed treatments and four herbicides. Thrips densities, both before and after herbicide applications, were counted.  Plant height and stand counts were monitored 5-7 days post treatment.  Plant injury (necrosis or chlorosis) was also recorded at this time. Nodes above white flower counts were made once just prior to cutout to determine differences in maturity, and yield was taken.