Bl. Hill et Ah. Purcell, ACQUISITION AND RETENTION OF XYLELLA-FASTIDIOSA BY AN EFFICIENT VECTOR, GRAPHOCEPHALA-ATROPUNCTATA, Phytopathology, 85(2), 1995, pp. 209-212
The blue-green sharpshooter (BGSS), Graphocephala atropunctata (Signor
et), is an efficient vector of Xylella fastidiosa Wells et al, the cau
sal bacterium of Pierce's disease of grapevine. In experiments to asse
ss changes over time in vector transmission efficiency and populations
of bacteria in BGSS, 81 of 120 BGSS that were fed for 12 h on infecte
d grapevine acquired the bacterium. Individual infective BGSS were exp
osed 4 times (1 h, and 7, 21, and 60 days after acquisition) to uninfe
cted grapevines for 3-h inoculation feeding periods to determine the e
fficiency of transmission to grapevine. After each inoculation efficie
ncy test, some BGSS were tested by culturing for X. fastidiosa to dete
rmine the bacterial population in the vector heads and bodies. Transmi
ssion efficiency increased from 56 to 99% between 1 h and 7 days post-
acquisition, and remained high thereafter (91% at 21 days and 76% at 6
0 days). Bacterial population size in the heads of the inoculative vec
tors also increased between 1 h and 7 days, but did not consistently i
ncrease further. Xylella fastidiosa was not recovered by culture from
about 40% of the inoculative insects. Populations below the detection
limit (100 bacteria) in the BGSS heads were enough for efficient trans
mission.