Efficacy of horizontal transmission of Cordyceps javanica in managing Drosophila suzukii populations

• Mating enables horizontal transmission of Cordyceps javanica in D. suzukii adult flies. • Inoculated males remained mating-competitive up to 48 h post-inoculation. • Direct inoculation caused 87–93% mycosis-related mortality in D. suzukii adult flies. • Secondary conidial transfer via male–male contact was minimal. • C. javanica infection reduced D. suzukii fecundity by 27–58 %. Drosophila suzukii (Matsumura) is a globally distributed pest of soft fruit crops with significant economic impact. This study evaluated the horizontal transmission of conidia of the entomopathogen, Cordyceps javanica, among D. suzukii adults under laboratory and semi-field conditions. Adults of both sexes acquired 1.5–1.8 × 10 8 conidia per adult when self-inoculated using a felt tube device. No significant differences in the mean number of matings per cage or the duration of mating were observed between non-inoculated adults (Control) or adults inoculated with viable conidia. A mean 1.2–6.0 × 10⁶ conidia per adult were successfully transferred during the first mating event. Inoculated adults exhibited high mortality rates (87–93 %), which exceeded those observed in conspecifics that acquired conidia during the first mating (57–75 %). Conidia transfer and fungal-induced mortality decreased significantly after the second mating event of males. Infected females in the first mating experienced a moderate reduction in fecundity (53 to 93 eggs/female) compared to non-infected females (130 eggs/female), but fertility remained unaffected (>96 % egg hatch rate). Non-inoculated males that were exposed to inoculated males, can acquire conidia due the male-male interactions, but those males exhibited minimal transmission of conidia to females during their first mating, resulting in negligible fungal-induced mortality to females (<2%). Similar mating rates between inoculated and non-inoculated males were observed in semi-field experiments, but low fungal-induced mortality was recorded under these conditions. Our findings reveal some limitations that can compromise the effectiveness of the use of this entomopathogen with a “lure and infect” approach to control D. suzukii .