ABSTRACT

Throughout the southern production region of the US, Roundup Ready cotton has become the standard. Glyphosate can control many of the common and troublesome weeds that are found in this region. However, long growing seasons and weed tolerance issues necessitate the use of residual herbicides applied preemergence (PRE), or either tank-mixed with, or as a sequential too, glyphosate. Studies were initiated to evaluate season long cotton response to various herbicide programs in Tifton and Plains GA, Rocky Mount and Lewiston NC, and Alexandria LA. Treatments included a 2 x 5 factorial arrangement of treatments of PRE applied Cotoran + Prowl or Cotoran + Prowl + Staple (08 oz/ac) with post-emergence (POST) applied Roundup Weathermax followed by (fb) Roundup WeatherMax, Roundup WeatherMax + Staple (0.4 oz/ac) fb Roundup WeatherMax + Staple (0.4), Roundup WeatherMax fb Roundup WeatherMax + Staple (0.6 oz/ac), Roundup WeatherMax fb Roundup WeatherMax + Staple (0.9 oz/ac), or Roundup WeatherMax fb Roundup WeatherMax fb Envoke (0.1 oz/ac). For the factorial analysis, PRE herbicide applications did not injure cotton. There was ~30% injury and 19% height reduction for the Tifton location for glyphosate + Staple POST applied. The other 4 locations exhibited less or no Staple injury. Envoke injured cotton at all locations but was most sever at Alexandria with 56% stunting and 17% height reduction. Season ending height, number of bolls, height/boll ratio, and seed cotton yield were not affected by any treatment. Plant map data for the positions one and two for nodes five through twenty five did not reveal any significant differences for boll development at the GA and NC locations.