COTTON (GOSSYPIUM SPP) LEAF BURN SYNDROME - A NEW COTTON PLANT DISORDER

Cotton ''leaf burn'' syndrome occurred widespread throughout the Imper ial Valley, California in 1989. The symptoms first appear in mid-July on leaves in most cases located on the exterior of the plant canopy. T he first visible indication was small brownish areas in the palms of l eaves. These areas enlarge and merge to dried necrotic areas surrounde d by silvery rings. Prior to the appearance of ''leaf burn'' symptoms, the dark green color of leaves often fades to a paler green. Stomata conductance and leaf transpiration of affected leaves were lowered, an d leaf water potentials and leaf temperatures were abnormally high in affected plants. Lint yields were reduced by an average of 30%. To dat e, cause(s) of the cotton ''leaf burn'' syndrome are unknown. However, soil applications of aldicarb (2-methyl-2- (methylthio) propionaldehy de-O- (methylcarbamoyl) oxime) alleviate the symptoms and increase cot ton yields.