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Ecology and Epidemiology

Geographic Information Systems and Geostatistics in the Design and Validation of Regional Plant Virus Management Programs. M. R. Nelson, Department of Plant Pathology, University of Arizona, Tucson 85721; R. Felix-Gastelum(2), T. V. Orum(3), L. J. Stowell(4), and D. E. Myers(5). (2)Campbell Research and Development, Carretera Internacional KM 149+284, Guasave, Sinaloa, Mexico; (3)Department of Plant Pathology, University of Arizona, Tucson 85721; (4)PACE Consulting, 1267 Diamond Street, San Diego, CA 92109; (5)Department of Mathematics, University of Arizona, Tucson 85721. Phytopathology 84:898-905. Accepted for publication 19 May 1994. Copyright 1994 The American Phytopathological Society. DOI: 10.1094/Phyto-84-898.

A regional management plan was designed and implemented for a multivirus, multivector, disease complex in tomatoes in the Del Fuerte Valley, Sinaloa, Mexico. The viruses include tobacco etch and cucumber mosaic with aphid vectors, a geminivirus complex with whitefly vectors, tomato spotted wilt with thrips vectors, and tomato mosaic with no known vector. Although the viruses and their vectors are biologically diverse, all are transmitted by flying insects, with the exception of tomato mosaic, and all except tomato mosaic are known to have alternate hosts among weeds and other crop plants in the area. Because of these similarities, we developed a risk-assessment process based on general virus infection hazards rather than specific viruses. The risk assessment helped to focus on actions that could be taken both locally and regionally to reduce early and damaging infections. Risk assessment and virus disease-incidence data were collected from 53 fields during 1990–1991 and 60 fields during 1991–1992. A geostatistical analysis of risk and incidence showed that both were spatially dependent variables with a variogram range of 20 to 25 km. Moving spatial averages (computed by kriging) indicated that the area east of Los Mochis was higher in risk and incidence than the area near Guasave during both seasons. Qualitative observations consistent with observed patterns of incidence suggest there are underlying landscape features more conducive to endemic plant virus diseases in the Los Mochis area than in the Guasave area.