Effects of floral resources on the longevity and parasitism of Cotesia vestalis Haliday (Hymenoptera: Braconidae) on Plutella xylostella (L.) (Lepidoptera: Plutellidae) in Vietnam

Parasitoids are important biological control of crop pests. In Vietnam, Cotesia vestalis is a native wasp species that has demonstrated its applicability as a natural insect pest enemy. Many adult parasitoids require food resources such as nectar and pollen to optimize their life cycles. Potential effects of yellow cosmos (Cosmos sulphureus), shrub verbena flower (Lantana camara), common zinnia (Zinnia elegans), and coriander flower (Coriandrum sativum L.) on the longevity and parasitism of C. vestalis were investigated. Results showed that nutrition resources from yellow cosmos (C. sulphureus) and shrub verbena flower (Lantana camara) significantly increased the longevity of C. vestalis in comparison with water (P < 0.001). Kaplan-Meier estimates of survival functions of female Cotesia vestalis exposed to different food sources indicated a significant difference in the treatments (P < 0.01). Male and female wasps feeding on Cosmos sulphureus, Lantana camara, and Coriandrum sativum survived significantly longer than wasps fed on water or Zinnia elegans. Parasitism efficiency of C. vestalis was tested on diamondback moth Plutella xylostella (L.) larvae for different food resources. Cosmos sulphureus, Lantana camara, Coriandrum sativum treatments gave the different mean number of emergence parasitoids per day compared to water treatment. Results implied that food resources from flowers benefitted the longevity of C. vestalis.