Spatial and seasonal distribution of egg parasitoids of the sharpshooter Tapajosa rubromarginata (Hemiptera: Cicadellidae: Proconiini) on feral Johnson grass and commercial citrus host in Argentina

Abstract

Hymenopterous egg parasitoids are considered promising biocontrol agents against insect vectors of the bacterium Xylella fastidiosa Wells. We studied the spatial and seasonal occurrence of the egg parasitoid guild of the sharpshooter Tapajosa rubromarginata (Signoret) (Hemiptera: Cicadellidae: Proconiini), a known vector of X. fastidiosa, in a commercial lemon orchard in Tucumán Province, Argentina. Egg masses of T. rubromarginata laid at three different heights were examined for two years, in spring and in summer, in order to determine the specific composition and abundance of its parasitoids. The overall rate of egg parasitoid emergence was about 54%. Fourteen species of parasitoids were obtained from egg masses of this host, nine belonging to the genus Cosmocomoidea Howard (Mymaridae) and the rest to five genera of Trichogrammatidae. The percentage of emerged wasps was higher in citrus than in the lower grassy stratum and it was similar in both seasons. Mymarids were generally more frequent and abundant than trichogrammatids, dominating as egg parasitoids of T. rubromarginata on citrus leaves, whereas trichogrammatids were more frequently found parasitizing egg masses of the same host on Johnson grass leaves. Three species were predominant among all the parasitoids, the trichogrammatid Zagella delicata De Santis and the mymarids Cosmocomoidea annulicornis (Ogloblin) and C. metanotalis (Ogloblin), accounting for about three-quarters of the emerged wasps; the other parasitoid species were occasionally or rarely found in the orchard.