Resource allocation and bionomics of indigenous and exoticCotesia(Hymenoptera: Braconidae) species reared onSesamia calamistis

Abstract

AbstractThe braconid larval parasitoidsCotesia chilonis(Matsumura),C. flavipesCameron and a strain ofCotesia sesamiae(Cameron) from coastal Kenya, reared at the International Centre of Insect Ecology and Physiology, were introduced at the International Institute of Tropical Agriculture in the Republic of Benin for suitability testing on West African stemborers prior to release.C. chiloniswas originally collected in Japan whileC. flavipeswas imported into Kenya from Pakistan. The host species used was the noctuidSesamia calamistis(Hampson), the most important noctuid maize pest in the region. All threeCotesiaspecies attacked and successfully developed in 2nd to 6th larval instar ofS.calamistisbut parasitoid-induced mortality was highest on second instars. On most instars,C. sesamiaeandC. flavipesproduced larger broods thanC. chilonis. Larvae parasitized byC. sesamiaedeveloped to the 6th instar and attained an average larval weight of 353 mg, while larvae parasitized byC. chilonisonly molted to the 4th instar and attained a maximum weight of 107 mg. The lower developmental threshold estimated from the non-linear regression of temperature on developmental rate was 15.9, 15.9 and 14.9°C forC. chilonis,C.sesamiaeandC. flavipes, respectively, while the maximum temperature was 34.2, 35.2 and 33.8°C, respectively. A maximum of four ovipositions were observed per female during a life span ranging from 1.3 days forC. chilonisandC. flavipesto 1.6 days forC.sesamiae. The largest adult progeny, intrinsic rate of increase and net reproductive rates were recorded at 28°C for all species. However, across temperatures,C. flavipesyielded the highest number of offspring, followed byC.sesamiaeandC. chilonis. The sex ratios did not vary significantly with species and temperature. Thus, the reproductive potentials ofC.sesamiaeandC. flavipeswere greater than that ofC. chilonis.