Survey of leafminers and their parasitoids to find endosymbionts for improvement of biological control

Agromyzid leafminers cause serious pest problems in Japan. These leafminers are parasitized by their native parasitoids. The objective of our research is to find symbionts that may be useful in improving the biological control of Agromyzid leafminers by using their native parasitoids in Japan. Among the four species of leafminers, we detected two strains of Wolbachia from Liriomyza trifolii (Burgess) (Diptera: Agromyzidae) and Liriomyza bryoniae (Kaltenbach) (Diptera: Agromyzidae). Although Wolbachia induces strong cytoplasmic incompatibility (CI) in L. trifolii, the level of Wolbachia infection in the population was not fixed and it was maintained at frequencies that must be regarded as unstable. Among the 15 species of leafminer parasitoids, we found a Wolbachia in Hemiptarsenus varicornis (Girault) (Hymenoptera: Eulophidae) and a Rickettsia in Neochrysocharis formosa (Westwood) (Hymenoptera: Eulophidae). H. varicornis was observed to be infected with Wolbachia very similar to that of the native leafminer L. bryoniae. This Wolbachia strain did not induce CI or parthenogenesis in H. varicornis. N. formosa is thelytokous and infected with Rickettsia, in practically all populations that were studied, the Rickettsia infection has reached fixation. Many leafminer parasitoids including N. formosa, belong to the family Eulophidae. It is possible that the Rickettsia of N. formosa may be used to render other Eulophidae thelytokous as well as a method to increase the biological control efficiency.