War of the wasps: is <em>Diadegma insulare</em> or <em>Microplitis plutellae</em> a more effective parasitoid of the Diamondback Moth, <em>Plutella xylostella</em>?

Abstract

Parasitism levels by Diadegma insulare (Muesebeck) (Hymenoptera: Ichneumonidae) and Microplitis plutellae (Haliday) (Hymenoptera: Braconidae) at various densities of their host, Plutella xylostella (L.) (Lepidoptera: Plutellidae), were assessed. Cages with densities of 10 hosts, 20 hosts, and 40 hosts were set up, with the cage volume (40 500 cm3) and number of wasps (2 females) remaining constant. The host populations were also exposed to the wasps for two different exposure times: 1 day and 3 days. The study showed that D. insulare was a better parasitoid overall, achieving a level of parasitism equal to or higher than M. plutellae at all densities. Microplitis plutellae performed best at a lower host density (76% ± 9% of 10 hosts vs. 43% ± 3% of 40 hosts). Diadegma insulare performed similarly at all densities tested (75% ± 5% of 10 hosts, 83% ± 4% of 20 hosts, and 79% ± 6% of 40 hosts). This suggests that D. insulare may be the better parasitoid overall and should be applied in severe, large-scale infestations, while M. plutellae may be better for small-scale infestations.

Selective effects of floral food sources and honey on life‐history traits of a pest–parasitoid system

“…Diadegma insulare (Cresson) (Hymenoptera: Ichneumonidae) is a dominant, solitary, synovigenic, larval parasitoid of diamondback moth, Plutella xylostella (L.) (Lepidoptera: Plutellidae), a destructive cosmopolitan pest of brassicaceous crops (Harcourt, ; Sarfraz et al., ; Lee & Heimpel, ). Diadegma insulare is one of the primary P. xylostella biocontrol agents in Canada and the USA (Harcourt, ; Sarfraz et al., ; Wold‐Burkness et al., ; Young, ). In North America, parasitism by this wasp varies from 50 to 98% in the field depending on host instars (Legaspi et al., ; Hutchison et al., ).…”