The bacterial blight pathogen, Xanthomonas malvacearum on cotton, Gossypium hirsutum, has not been found in San Joaquin Valley fields since 1961. Its ability to survive for up to seven years in dried cotton refuse might lead to long-term contamination of cotton gins, however. This would in turn provide an opportunity for the pathogen to again contaminate planting seed, with consequent recurrence of the disease in the field. Field eradication, dilution of contaminated refuse, and decreasing viability of the pathogen with age were expected to result in the disappearance of the pathogen from cotton gins in California. This report deals with attempts to determine whether contamination was still present, particularly in gins from which X. malvacearum had previously been isolated—as well as a large number of other gins in the area where bacterial blight was once prevalent.

California Planting Cotton Seed Distributors, Bakersfield, cooperated in this study and David Coplin gave technical assistance.