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Differential Pathogenicity of Corn Stunting Mollicutes to Leafhopper Vectors in Dalbulus and Baldulus species. L. V. Madden, Assistant professor, Department of Plant Pathology, The Ohio State University, Ohio Agricultural Research and Development Center, Wooster 44691; L. R. Nault, professor, Department of Entomology, The Ohio State University, Ohio Agricultural Research and Development Center, Wooster 44691. Phytopathology 73:1608-1614. Accepted for publication 13 June 1983. Copyright 1983 The American Phytopathological Society. DOI: 10.1094/Phyto-73-1608.

The effect of corn stunt spiroplasma (CSS) and maize bushy stunt mycoplasma (MBSM) on adult survival of six leafhopper vectors in Dalbulus spp. and one Baldulus sp. was determined. Newly discovered vector-mollicute associations were: D. gelbus-CSS, MBSM; D. guevarai-CSS, MBSM; D. quinquenotatus-CSS, MBSM; D. tripsacoides-CSS, MBSM; and B. tripsaci-CSS. Confirmed associations were: D. maidis-CSS, MBSM; D. elimatus-CSS, MBSM; and B. tripsaci-MBSM. Leafhopper survival was measured by the quartiles of the survival distribution (eg, median survival time [t50] and time to 25% survival [t25]), as well as estimated parameters of the Weibull model representing survival of each species. CSS reduced t50 for five species and t25 for six. Only D. maidis was unaffected by CSS. MBSM reduced t50 for only two species and t25 for five. D. elimatus and D. gelbus were unaffected by MBSM. The effect of MBSM was significantly less than CSS for four species. Rate of population decline, as measured by the Weibull scale parameter, was increased for six species exposed to CSS and five species exposed to MBSM. Affected species were the same as those determined by values of the 25% quartile. The differential pathogenicity of CSS and MBSM to their vectors can be rationalized according to the geographic distributions and host ranges of leafhoppers and pathogens.

Additional keywords: survival analysis, Tripsacum spp., Zea mays.