Age Preference and Fitness of Microplitis manilae (Hymenoptera: Braconidae) Reared on Spodoptera exigua (Lepidoptera: Noctuidae)

The larval parasitoid Microplitis manilae Ashmead (Hymenoptera: Braconidae) is a potential biological control agent of Spodoptera exigua (Hübner) (Lepidoptera: Noctuidae). To understand the preference and fitness of M. manilae on larval instars of S. exigua, we compared host choice, development, and life table parameters when different larval instars of S. exigua were supplied in the laboratory. Results showed that parasitism of 2nd or 3rd instar larvae was significantly higher compared with other instars. The intrinsic rate of increase (r), finite rate of increase (λ), net reproduction rate (R0) and mean length of a generation (T) were significantly affected by which larval instars were attacked. The maximum values of r, λ, R0 and T were observed when M. manilaeparasitized 2nd instar S. exigua larvae. Therefore, we conclude that the 2nd larval instar of S. exigua represents the optimum host stage and suggest that 2nd larval instar of S. exigua will be the most suitable host stage for mass production of M. manilae as well as the best instar to target for biological control in the field. El parasitoide larval Microplitis manilae Ashmead (Hymenoptera: Braconidae) es un agente de control biológico potencial de Spodoptera exigua (Hübner) (Lepidoptera: Noctuidae). Para entender la preferencia y desempeño de M. manilae en los instares larvales de S. exigua, comparamos la selección de hospedero, el desarrollo, y los parámetros de tablas de vida en diferentes instares larvales de S. exigua provistos en el laboratorio. Los resultados mostraron que el parasitismo en el segundo y tercer instar larval fueron significativamente más altos que en los demás instares. La tasa intrínseca de aumento de una población (r),la tasa finita de incremento natural (λ), la tasa reproductiva neta (R0) y el tiempo medio de una generación (T) fueron afectados significativamente por el instar larval atacado. Los valores mayores de r, λ, R0 y T fueron observados cuando M. manilae parasitó larvas de segundo instar de S. exigua. Concluimos que ...