Demography and Fitness of Anastatus japonicus Reared from Antheraea pernyi as a Biological Control Agent of Caligula japonica.

Abstract

Simple SummaryJapanese giant silkworm (JGS), Caligula japonica Moore, is an emerging defoliator pest of forest and fruit trees in East Asia, causing severe economic losses. In this study, we used eggs of the Chinese oak silkworm (COS), Antheraea pernyi Guérin-Méneville, as an alternative host to rear the dominant JGS egg parasitoid, Anastatus japonicus Ashmead. We showed that A. japonicus could be efficiently reared on COS eggs. Furthermore, A. japonicus reared from COS eggs had a high biological control potential against JGS. This study provides useful information on the demography, parasitism rate, and rearing methods of A. japonicus on COS eggs and the basis for developing a cost-effective biological control program against JGS using A. japonicus.Japanese giant silkworm (JGS), Caligula japonica Moore, is an emerging defoliator pest of forest and fruit trees in East Asia, causing severe economic losses. To develop a cost-effective biological control program against JGS, we used eggs of the Chinese oak silkworm (COS) Antheraea pernyi Guérin-Méneville as an alternative host to rear the most dominant JGS egg parasitoid Anastatus japonicus Ashmead. We compared the demographic parameters and total parasitism (killing) rates of A. japonicus parasitizing JGS and COS eggs using an age-stage, two-sex life table method. The results showed that A. japonicus performed differently on these two different hosts. Anastatus japonicus reared from COS eggs had a higher fecundity (369.7 eggs per female) and a longer oviposition period (35.9 days) on the COS than JGS eggs (180.9 eggs; 24.0 days). Consequently, A. japonicus parasitizing COS eggs had a higher intrinsic rate of increase (r = 0.1466 d−1), finite rate of increase (λ = 1.1579 d−1) and net reproductive rate (R0 = 284.9 offspring) than those parasitizing JGS eggs (r = 0.1419 d−1, λ = 1.1525 d−1, R0 = 150.0 offspring). The total net parasitism rate (the number of parasitized hosts in which the parasitoids successfully developed) of A. japonicus parasitizing COS eggs was 284.9, significantly higher than that of A. japonicus parasitizing JGS eggs (150.0), while the net non-effective parasitism rate (the number of parasitized hosts in which the parasitoids failed to develop) of the former (0.0) was significantly lower than that of the latter (9.6). These results suggest that A. japonicus can be efficiently reared on the alternative (or factitious) COS eggs, and the reared parasitoids have a high biological control potential against the target JGS.