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Geographic Distribution of Heterodera schachtii in the Imperial Valley of California from 1961 to 1983. E. P. Caswell, Graduate Research Assistant, Department of Nematology, University of California, Riverside 92521. I. J. Thomason, Professor, Department of Nematology, University of California, Riverside 92521. Plant Dis. 69:1075-1077. Accepted for publication 23 May 1985. Copyright 1985 The American Phytopathological Society. DOI: 10.1094/PD-69-1075.

The geographic distribution of the sugar beet cyst nematode (Heterodera schachtii) in the Imperial Valley of California was determined for the years 19611983 by computer mapping. Results show that the nematode has had a wide geographic distribution since 1961, with only the intensity of infestation increasing. During these years, an average of 20% of the fields planted each year were infested. Seven hundred twenty-five fields have been found to be infested, representing about 20,235 ha, or 11% of the total cultivated acreage in the Imperial Valley.