Developmental responses of the diamondback moth parasitoidDiadegma semiclausum(Hellén) (Hymenoptera: Ichneumonidae) to temperature and host plant species

Abstract

AbstractEffects of constant rearing temperature and the plant species fed upon by its hosts were investigated for several developmental parameters ofDiadegma semiclausum(Hellén), an important parasitoid of the diamondback moth,Plutella xylostella(L.). Temperature had highly significant effects on all developmental parameters measured, and effects were usually both linear and quadratic with increasing temperature. Host plant species, comprisingBrassica napusL.,Brassica rapaL. ssp.pekinensisandBrassica oleraceaL. var.capitata, also affected development of the parasitoid, and significant interactions were observed between plant species and rearing temperature for all developmental parameters measured. Development ofD. semiclausumoccurred successfully on all host plant species tested for the temperature range of 10 to 25°C. However, when itsP. xylostellahosts consumed leaf tissue ofB. napus, no specimens survived to pupate at 30°C, whilst pupation and adult eclosion occurred at 30°C onB. rapassp.pekinensisandB. oleraceavar. capitata. At high ambient temperatures, such as those characteristic of tropical or subtropical regions (especially at low elevations) or regions that undergo temperature increases due to climate change,P. xylostellais predicted to occur at a higher range of temperatures than its biocontrol agent,D. semiclausum. Effects of high temperatures are expected to be more profound on the parasitoid for some host plants than others, with greater developmental limitations for the parasitoid onB. napusthan onB. rapaorB. oleracea.