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

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.

Chinese oak silkworm Antherae pernyi egg, a suitable factitious host for rearing eupelmid egg parasitoids.

BACKGROUND: Eupelmid egg parasitoids in the genera Anastatus and Mesocomys are important biological control agents for lepidopterous and hemipterous pests worldwide. The egg of Chinese oak silkworm Antheraea pernyi has been widely used for mass rearing of Trichogramma parasitoids. This study evaluated the suitability and optimal use methods of A. pernyi egg as a factitious host for the rearing of six eupelmid egg parasitoids (Anastatus fulloi, Anastatus gansuensis, Anastatus japonicus, Anastatus meilingensis, Mesocomys albitarsis and Mesocomys trabalae). Each parasitoid was tested for its oviposition preference and offspring performance on various differently treated host eggs (extracted from virgin moths or laid naturally by virgin or mated moths, and washed or unwashed prior to the use) in both no-choice and choice tests. RESULTS: All treated A. pernyi eggs were readily parasitized by the six parasitoids. In general, A. gansuensis and M. trabalae preferred washed over unwashed eggs regardless of the fertilization status of host eggs, A. fulloi and A. meilingensis parasitized more unfertilized than fertilized host eggs, and A. japonicus and M. albitarsis did not show a preference among differently treated host eggs. Host egg treatment did not significantly affect offspring fitness (development time, survival, sex ratio and body size) nor reproductive potential of developed adult females for each parasitoid species, except for M. albitarsis (whose females contained more eggs when reared from unfertilized than fertilized host eggs). CONCLUSION: Results suggest that manually extracted, unfertilized and washed A. pernyi eggs are most suitable for mass rearing of these eupelmid egg parasitoids in biological control programs.

Parasitism and Suitability of Aprostocetus brevipedicellus on Chinese Oak Silkworm, Antheraea pernyi, a Dominant Factitious Host.

Aprostocetus brevipedicellus, a eulophid gregarious egg parasitoid of lepidopterous pests, is a potential biological control agent for the control of many forest pests. A dominant factitious host, Antheraea pernyi, has been widely used for mass rearing several parasitoids in China. However, whether A. pernyi eggs are suitable for A. brevipedicellus rearing remains unclear. Here we evaluated A. brevipedicellus parasitism and fitness of their offspring on A. pernyi eggs with five different treatments, including manually-extracted, unfertilized and washed eggs (MUW), naturally-laid, unfertilized and washed eggs (NUW), naturally-laid, unfertilized, and unwashed (NUUW) eggs, naturally-laid, fertilized and washed eggs (NFW), and naturally-laid, fertilized and unwashed eggs (NFUW). The results showed that A. brevipedicellus could parasitize host eggs in all treatments but significantly preferred MUW eggs to other treatments. Moreover, A. brevipedicellus preferred unfertilized eggs to fertilized eggs and parasitized more washed eggs than unwashed. The pre-emergence time of parasitoid offspring emerging from fertilized eggs was shorter than that from unfertilized eggs. More parasitoid offspring emerged from unwashed eggs than that from washed eggs. The offspring emergence rate was high (>95%) and also female-biased (>85%) among all egg treatments. The egg load of female parasitoid offspring emerging from MUW and NUW eggs was 30-60% higher than the remaining treatments. Overall, MUW eggs of A. pernyi are the most suitable for the mass production of A. brevipedicellus.