Effects of Gender, Origin, and Age on Transmission of Xylella fastidiosa to Grapevines by Homalodisca vitripennis (Hemiptera: Cicadellidae)
Homalodisca vitripennis (Germar) (Hemiptera: Cicadellidae) is an invasive vector of Xylella fastidiosa, the causal agent of Pierce's disease of grapevines (Vitis vinifera L.). Transmission efficiency of X. fastidiosa to grapevines by H. vitripennis originating from two geographically separated populations in California (Riverside and Bakersfield) based on gender and age was evaluated. To evaluate transmission efficiencies among groups, insects were given a 96-h acquisition access period on infected grapevines and caged in groups of five on healthy grapevines for a 72-h inoculation access period. At the conclusion of tests, polymerase chain reaction determined that a mean +/- SD of 0.98 +/- 1.02 X. fastidiosa-positive H. vitripennis were present on each grapevine and that 29% of test plants were infected. Acquisition and retention of X. fastidiosa was not affected by vector origin, gender, or age. The probability that a grapevine was infected 12 wk after the inoculation access period increased with the number of X. fastidiosa-positive H. vitripennis per plant. Gender had no effect on inoculation success and main effects of insect origin and age on inoculation success were minor. Collectively, the result indicated that H. vitripennis origin, gender, and age did not affect acquisition and retention of X. fastidiosa and had only minor effects on inoculation success under laboratory conditions. Accordingly, rates of pathogen spread in the field are more likely to be affected by local biotic and abiotic factors that differentially affect H. vitripennis abundance and movement based on origin, gender, and age than inherent differences in transmission efficiencies among these groups.