ANGULAR LEAF SPOT of Cotton (Gossypium hirsutum), caused by the bacterium Xanthomonas malvacearum, became established in California in about 1951. By 1962, however, sanitation had eradicated it from cotton fields, and attempts in 1966-67 to demonstrate cotton-gin-contamination failed even though contamination had been readily demonstrated in 1958-60, when the disease was widespread.

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