Acquisition and transmission of corn stunt spiroplasma by its leafhopper vector Dalbulus maidis

As the acquisition access period of Dalbulus maidis on infected maize increased from 15 min to 7 days, the incubation period of corn stunt spiroplasma (CSS) in the insect decreased from 27 days to 8 days and the final proportion of transmitting insects increased from 5% to 100%. After 7 days access the median incubation period (IPsO) was 14.3 days (IP₅₀ females = 12.9 days: IP₅₀ males =16.8 days), while the proportion of transmitting insects increased from 4. 3% (9 days after the start of acquisition access) to a maximum of 93% (after 22 days), before decreasing. Females started transmitting significantly earlier and a greater proportion transmitted each day than males, until day 22 when both sexes transmitted equally. Of the insects which transmitted CSS, 29% did so continuously until death; 66% failed to transmit during the last 1–3 days, and 5% transmitted intermittently towards the end of their life. During daily transfer, females were more likely to infect plants consecutively (up to 25) than males, and females infected the higher proportion of test plants. As the transmission access period was increased from 1 h to 72 h, the proportion of transmitting insects increased from 22.5% to 97.3% and the incubation period in maize decreased.