Vector fecundity reduced by Western X-disease

Abstract

Western X-disease (WX), previously thought to be caused by a virus, appears to be due to a mycoplasma-like organism transmitted by certain leafhoppers. In the vector Colladonus montanus, the WX agent produced lesions in a number of tissues, reduced fecundity, and caused premature death. The fecundity of C. montanus leafhoppers was impaired by the WX agent when infection was acquired either by injection with infectious leafhopper extracts or by feeding on diseased celery plants. The difference in fecundity between insects injected with the WX pathogen and those injected with noninfectious extracts remained approximately constant through time. In contrast, in experiments with insects that had acquired WX infectivity through feeding, the fecundity curve of infective insects declined rapidly during the last 4 weeks whereas that of the healthy controls rose and then remained almost constant throughout this portion of the test period. The effect on fecundity was more extreme in insects that fed on WX plants than it was in those leafhoppers that fed only on healthy plants and acquired WX infectivity by injection. These results suggest that feeding on diseased plants reduces the fecundity of C. montanus in some manner over and beyond that resulting from the action of WX per se on the reproductive system of this vector. The nutrition derived by leafhoppers from diseased plants is adequate for normal longevity, but may be partially deficient in some constituents essential to normal fecundity.