Does the seasonal phenotype of Drosophila suzukii influence cellular immunity and parasitisation?

Abstract

Controlling the worldwide invasive pest Drosophila suzukii remains a challenge. One promising biological method for managing this pest is the use of larval and pupal parasitoids. Unfortunately, most of the larval parasitoids fail to successfully parasitise D. suzukii larvae in laboratory experiments due to the high immunity of the pest. So far, only the summer phenotype (summer morph) of D. suzukii has been tested for parasitisation. However, the winter phenotype (winter morph) is the dominant form of D. suzukii throughout the year in the northern hemisphere. Therefore, this study investigates the immunity during parasitisation for both phenotypes using the larval parasitoid Asobara japonica and the pupal parasitoid Trichopria drosophilae. It is the first to compare across all life stages the immunity of the winter phenotype to the summer phenotype of not only D. suzukii but also D. melanogaster. Our results indicate differences in the immunity between the two phenotypes for larvae, pupae, and adults. However, the degree and direction of these differences were inconsistent across the different life stages of D. suzukii. The findings have important implications for the integrated pest management (IPM) of D. suzukii.