wasps for ecological pest control-a laboratory experiment.

Biological control of pest insects by natural enemies may be an effective, cheap and environmentally friendly alternative to synthetic pesticides. The cosmopolitan parasitoid wasp species Wesmael and Say (Hymenoptera: Braconidae) use lepidopteran species as hosts, including insect pests like or . Here, we compare the reproductive success of both species on in a laboratory experiment. We asked (1) how the reproductive success on a single host larva changes with temperature, (2) how it changes with temperature when more host larvae are present and (3) how temperature and availability of host larvae influence the efficacy of species as biological control agents. In general, differences between and have been small. For rearing both species in the laboratory on one host larva, a temperature between 20-27 °C seems appropriate to obtain the highest number of offspring with a female-biased sex ratio. Rearing the braconid wasps on more than one host larva revealed a higher number of total offspring but less offspring per host larva on average. Again, highest numbers of offspring hatched at 27 °C and the sex ratio was independent from temperature. Although no parasitoids hatched at 12 °C and only few at 36 °C, host larvae were still paralyzed. The efficacy of was higher than 80% at all numbers of host larvae presented at all temperatures while the efficacy of was less than 80% at 12 °C and 27 °C at low numbers of host larvae presented. In conclusion, practitioners can use either or at low and high temperatures and at varying host densities to achieve high pest control efficacy.