ABSTRACT

BXN® cotton is resistant to the herbicide bromoxynil which effectively controls many broadleaf weeds following field application of (BUCTRIL® 4EC) in cotton. BXN® seed lots must be tested prior to sale to insure that seed is indeed resistant to the herbicide to prevent crop injury. Delinted cottonseed is planted with equidistant spacing in nursery flats and grown at 7,500 lumens m-2 at 30 - 32oC with a 24-hr photoperiod. Spraying a 3,642 ppm bromoxynil solution over-the-top until runoff, to actively growing seedlings at the cotyledon to one-leaf stage, and then re-applying the herbicide two days later in the laboratory is a valid and cost-effective means to determine percent purity of cottonseed samples. Susceptible seedlings appear desiccated or burned at two days after herbicide application, followed by complete necrosis.