Overwintering survival, starvation resistance, and post-diapause reproductive performance of Nezara viridula (L.) (Hemiptera: Pentatomidae) and its parasitoid Trichopoda giacomellii Blanchard (Diptera: Tachinidae)

The interaction between diapause in Nezara viridula and parasitism by the introduced Trichopoda giacomellii was studied at Moree in northern NSW, Australia. N. viridula adults were shown to enter diapause progressively over a 6–8 week period commencing in mid-May. Fifty percent of unparasitised N. viridula males and 60% of females survived the winter period to re-emerge in early August. This population survived in the field until late spring and had an average post-diapause fecundity of 146 eggs per female. No parasitised N. viridula adults survived the winter period. Parasitoid larvae underwent a protracted development with pupariation occurring in mid-winter. Twenty-two percent of parasitised N. viridula adults produced parasitoid puparia. The remaining 78% of N. viridula adults died prior to parasitoid larvae completing development. Host starvation was shown not to influence parasitoid development success. Emergence of T. giacomellii adults from these puparia coincided with the re-appearance of N. viridula adults in the field during early to late spring. Those T. giacomellii present as puparia in the soil during May emerged during mid-winter in asynchrony with N. viridula. Clearly, aspects of the ecological requirements and life-history of T. giacomellii do not match those of its host N. viridula. Implications for the success or otherwise of T. giacomellii as a biological control agent for N. viridula in Australia are discussed.