Horizontal transmission of Metarhizium anisopliae among laboratory populations of Ceratitis capitata (Wiedemann) (Diptera: Tephritidae)

The horizontal transmission capacity of the autochthonous Metarhizium anisopliae strain EAMa 01/58-Su among Ceratitis capitata adults was evaluated in laboratory tests. Males and females inoculated either with dry conidia or with wet conidia became infected exhibiting 95.0–100.0% mortality rates with mycosis and Average Survival Time values of 8.30–9.30 days. Both the inoculation method and the sex, however, had a significant effect on the effectiveness of transmission; thus, inoculation with dry conidia resulted in higher transmission rates than inoculation with wet conidia. In both inoculation methods, the male-to-female rate of transmission ranging between 90.0% (wet) and 100.0% (dry) was higher than the female-to-male rate, which varied from 60.0% (wet) to 90.0% (dry). While the effectiveness of transmission was highly correlated with the sexual proportion between inoculated males and clean females, the mean number of females infected by males tended to be constant (4.5–5.5). SEM micrographs of clean C. capitata females than had been paired during 24 h with inoculated males revealed the presence of conidia in the dorsal thoracic and abdominal sclerites, with many conidia either germinated or not being observed in the female ovipositor. The horizontal transmission potential of M. anisopliae strain EAMa 01/58-Su was evaluated against C. capitata in cage experiments using an experimental autoinoculation device consisting of a plastic mineral water bottle. Adults of C. capitata of both sexes entered and exited the autoinoculation device for the 48 h of exposure and became infected with the fungus with 100.0% male and female mortality followed by mycosis. Moreover, adults of C. capitata that were maintained for 48 h in contact with the autoinoculation device transmitted the fungal inoculum to clean adults of the opposite sex, with 95.0% mortality rates of clean males or females. These results reveal the relevant contribution that horizontal transmission has on the overall efficacy of fungal treatment for medflies, and they indicate that medflies might potentially be controlled through the use of EAMa 01/58-Su strain in an autoinoculation device.