Angular leaf spot of cotton is caused by the bacterium—Xanthomonas malvacearum—which enters the plant through wounds or natural openings. Circular translucent lesions on cotyledons, angular lesions on leaves, systemic infection of leaves, stem lesions, and boll rot—all caused by the pathogen—have been observed in California. Yield of cotton may be affected by the disease indirectly, by stunting and premature defoliation of plants, or directly, by loss of bolls due to boll rot.

R. D. Martin, California Planting Cotton Seed Distributors, Bakersfield, participated in the studies reported in the foregoing article.

Marvin Hoover, Extension Cotton Specialist, University of California, aided in collecting samples from cotton gins.

The above progress report is based on Research Project No. H-1651.