Horizontal and Vertical Transmission of <i>Beauveria bassiana</i> : Effects on Population Growth Rates in <i>Ceratitis capitata</i>

ABSTRACT The use of sterile insects as vectors of Beauveria bassiana (Hypocreales: Clavicipitaceae) conidia can be a successful strategy for controlling several fruit fly species. The fungal infection can last 3 or 4 days in sterile males before killing them, but infected wild females will experience reduced offspring production throughout their lifespan before dying, which represents an additional suppression factor in the pest population. Our objective here was to determine the effect of the density of sterile medfly ( Ceratitis capitata , Wied.) (Diptera: Tephritidae) males inoculated with B. bassiana on the transmission to wild males and females, and the impact on the growth rate of the target population. The study was carried out in medfly‐infested coffee areas in Guatemala under semi‐field conditions. We used wild medfly adults that emerged from larvae collected from infested coffee berries and sterile males of the Temperature‐Sensitive Lethal (TSL) strain provided by the Moscamed facility located in Metapa de Domiguez, Chiapas, Mexico. We tested the performance of different proportions of sterile males inoculated with conidia of the B. bassiana strain AES (Agrícola El Sol) in competition with wild males to obtain matings with wild females. Offspring was obtained by exposing guava fruits as hosts and fecundity was determined during 10 consecutive days. Sexual competitiveness was not affected in treated sterile males during the first 3 days. Horizontal transmission to wild females and males was 73.6% and 70.8%, respectively. Fecundity was reduced by 27.4% in wild females from treatments with inoculated sterile males compared to wild females from treatments with non‐inoculated sterile males. However, egg hatching was 33.6% higher in treatments with inoculated sterile males. The Sterile Insect Technique (SIT) boosted with Beauveria bassiana conidia was effective in reducing the progeny of Ceratitis capitata and its efficacy was directly related to the sterile: fertile male ratio. This reduction resulted from the direct effect of increasing mortality and reducing fertility during the infection process.