Evidence of two-sex life table analysis supporting Anastatus japonicus, a more effective biological control agent of Caligula japonica compared with other two Anastatus species

Abstract

Japanese giant silkworm (JGS) Caligula japonica, is an emerging defoliator pest of forest and fruit trees, causing serious economic losses to walnut, ginkgo and chestnut in East Asia. To identify the dominant parasitoids of JGS, we compared biological control potential and fitness of three Anastatus species (A. fulloi, A. meilingensis and A. japonicus), which are natural egg parasitoids of JGS collected in northwestern China, on JGS eggs using age-stage, two-sex life table method. The results showed that three Anastatus species reared on suitable factitious host Chinese oak silkworm Antheraea pernyi were readily parasitized and completed their development and emergence from target JGS eggs. Anastatus japonicus had higher fecundity (F: 189.8 offspring/female) and longer oviposition days (Od: 24.36 d) than that of A. fulloi (F: 66.7 offspring/female, Od: 12.32 d) and A. meilingensis (F: 39.9 offspring/female, Od: 8.61 d). Consequently, the intrinsic rate of increase (r), finite rate of increase (λ) and net reproductive rate (R0) of A. japonicus (r: 0.1404 d−1, λ: 1.1508 d−1, R0: 146.5 offspring/individual) were significantly higher than those of A. fulloi (r: 0.1122 d−1, λ: 1.1187 d−1, R0: 50.9 offspring/individual) and A. meilingensis (r: 0.1213 d−1, λ: 1.1289 d−1, R0: 35.2 offspring/individual). In addition, the net killing rate (C0) of A. japonicus was 155.6 (eggs/female), which was significantly higher than that of A. fulloi (51.5 eggs/female) and A. meilingensis (36.7 eggs/female). Our results showed that A. japonicus had the highest parasitism capacity among three Anastatus species tested on target eggs and suggest that it may be the most suitable biocontrol agent for JGS.