Performances of six eupelmid egg parasitoids from China on Japanese giant silkworm Caligula japonica with different host age regimes

Description

The Japanese giant silkwormCaligula japonicaMoore is an emerging defoliator pest of forest and fruit trees, causing severe economic losses in East Asia. To identify biological control agents for this pest, we comparatively evaluated six indigenous eupelmid egg parasitoids (Anastatus fulloi,A. gansuensis,A. japonicus,A. meilingensis,Mesocomys albitarsisandM. trabalae) from China, in terms of their performances (number of parasitized eggs, developmental time, offspring emergence and sex ratio) onC. japonicaeggs of four different ages (0, 10, 20 and 30-d old). Results showed that all six parasitoids readily parasitizedC. japonicaeggs of all tested ages, butA. japonicuswas the most efficient species based on the number of parasitized eggs, followed byM. albitarsisandM. trabalae, and the other three parasitoid species. All fourAnastatusspecies parasitized more old than young eggs, whileM. albitarsisdid not show a strong host age preference andM. trabalaeparasitized the oldest less than young eggs. For all host ages, developmental time was longest inA. gansuensisand shortest inM. albitarsis, offspring emergence was high (> 90%), and progeny was strongly female biased (> 70%) among all parasitoids except forA. gansuensiswhich produced all female progeny. Portions ofA. japonicusoffspring (< 13.1%) entered diapause as pre-pupae. Accordingly,A. japonicus,M. albitarsisandM. trabalaewere identified as the most suitable agents againstC. japonica. This information may also help improve rearing and field-release protocols, in terms of host age-related effects on these parasitoids.

Abstract

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