Effect of Fungicide and Application Timing on Target Spot in Louisiana

Target spot, caused by the fungus Corynespora cassiicola, is an emerging issue in cotton (Gossypium hirsutum) in the Mid-South.  The disease has been an annual problem in Alabama and Georgia for the past 10 years.  In Louisiana, the disease has historically been an occasional problem in isolated areas; however, during the 2014 growing season, target spot was widespread in cotton producing areas of central and northeast Louisiana.  In some cases cotton fields were observed to be two-thirds defoliated as a result of the disease.  Because of the severity of the disease in 2014, Louisiana producers and consultants are interested in potential management options if the disease becomes an annual problem.  In 2014, two trials were conducted at the Dean Lee Research Station (DLRS) in Alexandria, LA, and one trial was conducted at the Macon Ridge Research Station (MRRS) near Winnsboro, LA.  At DLRS one trial was planted to Delta & Pine Land (D&PL) 1133, while the other was Phytogen (PHY) 499.  Both trials at DLRS had the exact same treatments with Headline (6 fl oz/A), Priaxor (4 fl oz/A), Quadris (6 fl oz/A), or Topguard (7 fl oz/A) applied at the 1^st or 3^rd week of bloom.  The trial at MRRS was planted to Phytogen 499 and treatments consisted of Headline (6 fl oz/A), Priaxor (4 fl oz/A), or Quadris (6 fl oz/A) applied at the 1^st week of bloom; Headline (6 fl oz/A) or Priaxor (4 fl oz/A) applied the 1^st and 3^rd week of bloom; or Headline (6 fl oz/A) at the 1^st week of bloom followed by Priaxor (4 fl oz/A) at the 3^rd week of bloom and vice versa.  Results from these trials will be presented.