Does Wolbachia Infection Change the Overwintering Ability of Trichogramma brassicae (Hymenoptera: Trichogrammatidae)?

The overwintering ability of a biological control agent helps predict potential survival and establishment in natural conditions. Here, we compared the overwintering ability in sexual and asexual Trichogramma brassicae Bezdenko, a key natural enemy of Lepidopteran pests in Iran over two consecutive winters in central Alborz Mountains. Our aim was to investigate the effect of Wolbachia infection on the overwintering rate of T. brassicae after emergence in the subsequent year. We also wanted to know whether there is any difference in the overwintering capacity of T. brassicae populations either in terms of exposure date or emergence date. Parasitized host eggs were exposed under outdoor conditions between 8 October and 27 November 2013 and between 8 October and 11 December 2014. Samples were checked weekly until adult emergence of overwintered individuals in the following spring, and proportion of adult emergence was recorded on each exposure date. Our results demonstrated that both populations were able to overwinter in natural conditions of central Alborz Mountains; however, sexual T. brassicae was more successful in overwintering than asexual one. No differences were observed in the emergence date and maximum emergence rate between two populations. Our study clearly identified a potential negative impact of Wolbachia on fitness of T. brassicae by a lower rate of emergence.