STUDIES ON PREVENTION OF COTTON LEAF BURN SYNDROME IN THE IMPERIAL-VALLEY, CALIFORNIA

Insecticides, fungicides, a bactericide, and an antioxidant were studi ed at Brawley and Holtville, CA in 1991 to evaluate their potential fo r preventing or alleviating cotton ''leaf burn'' symptoms. The ''leaf burn'' condition occurred widespread througout the Imperial Valley, CA in 1989 and 1990 with devastating reductions in cotton yields. Result s of the present studies suggest that foliar application of liquid oxa myl (methyl-N' methyl-N-((methylcarbamoyl)oxy)-1-thiooxamimidate) or s oil application of aldicarb (2-methyl-2-(methylthio) propionaldehyde-O -(methylcarbamoyl) oxime) prevented occurrence of the cotton plant dis order and increased cotton yields. This was supported by plant physiol ogical indices of lower leaf temperatures, higher transpiration rates, lower leaf water potentials, and higher cotton yields as compared to the untreated plants. The primary cause(s) of the cotton ''leaf burn'' syndrome have not been determined, but results of our studies suggest that air pollution and irrigation water stress are not directly invol ved.