Abstract: 【Aim】 To identify the effects of induced plant resistance on the development of the beet armyworm, Spodoptera exigua (Hübner) and its endoparasitoid Meteorus pulchricornis (Wesmael).【Methods】 The plants of Brassica campestris were induced by herbivory damage (HD), mechanical damage (MD), or spraying 0.01, 0.1 and 1 mmol/L exogenous methyl jasmonate (MeJA), and used to feed the newly-hatched larvae of S. exigua, which then were exposed to the parasitism of M. pulchricornis. The developmental performances of the host and its parasitoid were observed. 【Results】 The survival rate of S. exigua larvae fed on plants treated by HD and MeJA treatments decreased significantly, and the survival rate of S. exigua larvae had a negative correlation with MeJA concentration. The larval body weight of S. exigua fed on the plants subjected to 0.1 mmol/L MeJA treatment was significantly lower than that of the control. When S. exigua larvae fed on the plants subjected to HD and 0.1 mmol/L MeJA treatments, the mortality of the larval parasitoid M. pulchricornis increased as compared with the control and its pupation rate reduced, and the body weight of adult parasitoid under 0.1 mmol/L MeJA treatment was lower than that of the control. The ovarian development of M. pulchricornis did not differ between treatments, and each ovary consisted of 8-10 ovarioles with 7-10 mature eggs, each 350 μm long and 78 μm wide, at 24 h post eclosion. 【Conclusion】 These results suggest that the resistance inB. campestris plants induced by HD and MeJA has negative impacts on the survival and body size of S. exigua larvae, which consequently has negative effects on the development of its parasitoid M. pulchricornis.

Key words: Meteorus pulchricornis, Spodoptera exigua, induced resistance, herbivory damage, methyl jasmonate, growth and development, ovarian development