Performance and host finding behavior in relation to host age of Cosmocomoidea annulicornis, egg parasitoid of a sharpshooter vector of the citrus variegated chlorosis

Abstract

Cosmocomoidea annulicornis (Ogloblin) (Hymenoptera: Mymaridae) is a solitary egg parasitoid of the sharpshooter Tapajosa rubromarginata (Signoret) (Hemiptera: Cicadellidae), vector of the bacterium Xylella fastidiosa Wells, which causes citrus variegated chlorosis in citrus plants. The disease has been reported in several South American countries affecting commercial citrus orchards. A description on the general morphology of the egg of T. rubromarginata and the stages of embryonic development was performed to evaluate the developmental stages that C. annulicornis is able to attack. An assessment on parasitoid parasitism and emergence rates, developmental time and sex ratio was performed to determine the suitability of eggs of different ages (24, 48, 72, 96, 120 and 144 h old) as hosts. In addition, female response to olfactory cues was tested in a Y-tube olfactometer to assess whether host age affects foraging behavior. Embryogenesis would begin after 48 h from oviposition. Parasitism rate significantly varied among host ages, sharply decreasing in older eggs. Emergence rate and sex ratio of the offspring were affected by host age. Parasitoid developmental time was shorter for older host ages (120–144 h). Olfactometer assays showed that C. annulicornis females successfully detected plants carrying host eggs and that host age did not affect host searching behavior. Results reported suggest that host age influences parasitism efficiency of C. annulicornis, but does not play a major role in modulating host searching behavior in response to odors emitted by plants carrying eggs of different ages, as females did not discriminate between fresh and older eggs.