The effect of flower morphology on the longevity of Diadegma semiclausum (Hymenoptera: Ichneumonidae)

Abstract

Refugia plants can support the biological control of plant pests by increasing the presence and fitness of parasitoids. One of the factors that determine the suitability of refugia plants with parasitoids is the flower morphology. This study used Diadegma semiclausum, a parasitoid of cabbage pest, Plutella xylostella. This study aimed to determine the effect of refugia plants' flower morphology on the longevity of D. semiclausum adults. Refugia plants used were Rorippa indica, Brassica rapa, Ageratum conyzoides, and Sphagneticola trilobata. Research methods consist of insect rearing and plant preparation, testing refugia flowers' influence on parasitoid longevity, and measuring flower morphology (corolla length and aperture, and nectar location). The results showed all refugia flower treatments could increase the parasitoid longevity compared to control (1.71-3.69 times). The best effect was demonstrate by the R. indica treatment, followed by B. rapa, A. conyzoides, and S. trilobata. Correlation and regression analysis showed that the increasing corolla aperture and length positively affected parasitoid longevity. Flowers with exposed nectar positions (R. indica and B. rapa) makes the parasitoid easy to access, even though the corolla flowers were longer than A. conyzoides and S. trilobata.