Differential Pathogenicity of Corn Stunting Mollicutes to Leafhopper Vectors inDalbulusandBaldulusspecies

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Abstract
The effect of corn stunt spiroplasma (CSS) and maize bushy stunt mycoplasma (MBSM) on adult survival of 6 leafhopper vectors in Dalbulus spp. and 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. tripasci-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 (e.g., 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 5 spp. and t25 for 6. Only D. maidis was unaffected by CSS. MBSM reduced t50 for only 2 spp. and t25 for 5. D. elimatus and D. gelbus were unaffected by MBSM. The effect of MBSM was significantly less than CSS for 4 spp. Rate of population decline, as measured by the Weibull scale parameter, was increased for 6 spp. exposed to CSS and 5 spp. 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.