Evaluation of asexual Wolbachia-infected Trichogramma brassicae performance in greenhouse and field conditions

In some Trichogramma species, parthenogenesis is mostly induced by intracellular symbiotic Wolbachia bacteria. Populations of this egg parasitoid wasp that produce more female progeny can potentially have higher fitness. After finding a thelytokous Wolbachia-infected native strain of Trichogramma brassicae, a study was conducted to evaluate its parasitism rate and foraging efficiency in the greenhouse and field conditions. Treatments included a Wolbachia-associated thelytokous T. brassicae strain (A), an uninfected natural bisexual population (B), and an antibiotic-cured bisexual population (CB). Results of the equal female wasps’ releases revealed no significant difference among the three populations regarding their dispersal ability, mean parasitized eggs (PE) and parasitized bait cards (PBC) per female on forage corn (SC704) in greenhouse condition. However, when equal wasp individuals were released (e.g. 100 individual wasps including males in the bisexual populations), the number of mean parasitized egg batches by asexual line (7.57 PBC) was significantly higher compared with that in B and CB bisexual populations (4.50 and 4.97 PBC, respectively). Similarly, in the corn field condition, the highest number of parasitized bait cards and parasitized egg numbers belonged to asexual wasp (A) (1.94±0.21 PBC and 7.26±1.2 PE/female) compared with those in B (1.56±0.39 PBC and 5.46±1.99 PE/female), and CB (1.6±0.3 PBC and 5.82 ± 1.96 PE/female) bisexual populations. In general, it can be concluded that the use of an asexual Wolbachia- associated line of T. brassicae can increase the efficiency of this biological control agent at the field level in addition to reducing mass production costs.