Effect of Phymatotrichum Root Rot on Yield and Seed and Lint Quality in Gossypium hirsutum and G. barbadense. E. N. Mulrean, Assistant Plant Pathologist, Department of Plant Pathology, University of Arizona, Tucson 85721. R. B. Hine, Professor, Department of Plant Pathology, University of Arizona, Tucson 85721, and J. P. Mueller, Dow Chemical Company, Walnut Creek, CA 94596. Plant Dis. 68:381-383. Accepted for publication 31 October 1983. Copyright 1984 The American Phytopathological Society. DOI: 10.1094/PD-68-381.

Yields of field-grown, Phymatotrichum-infected, upland cotton (Gossypium hirsutum) and Pima cotton (G. barbadense) were reduced 10 and 13%, respectively, compared with healthy plants. Losses were greatest (0.46 bales per infested hectare) in upland cotton grown in monoculture and less (0.26 bales per infested hectare) when grown in rotation with barley, wheat, sorghum, and sudangrass. Yield reduction in infected upland cotton had two components: fewer bolls set and less lint per mature boll. Yield losses in Pima cotton were associated with lower total boll set. Fibers from infected upland cotton plants were significantly shorter, less uniform, and finer than fibers from healthy plants. Fiber quality in Pima cotton was adequate in spite of root rot. Seed quality and germinability were reduced in seeds collected from infected plants of both varieties.

Keyword(s): cotton root rot, crop loss assessment.