Origin of the diamondback moth

 

Diamondback moth, Plutella xylostella (L.) (Lepidoptera: Plutellidae), feeds only on plants belonging to the family Brassicaceae. It is assumed that the diamondback moth evolved on plants from this family. Because cultivated brassicas are considered of European origin, it was suggested and since then widely accepted that the diamondback moth had also originated in the same area and spread with the cultivated brassicas around the world. Twenty-two species of parasitoids and hyperparasitoids have been reared from larvae and pupae of diamondback moth in South Africa. Some are specific and known only from South Africa, indicating a very long association between parasitoids and the pest in the region. This minimizes the possibility that the diamondback moth arrived in the region with the cultivated brassicas 300 yr ago.

A total of 175 wild plant species in the Brassicaceae have been recorded in South Africa, of which 32 are exotic species. It is likely that diamondback moth evolved on indigenous brassicas in the region. Diadromus collaris Gravenhorst (Hymenoptera: Ichneumonidae), which has been widely used in biological control projects against diamondback moth, is an abundant pupal parasitoid of diamondback moth in South Africa. D. collaris is arrhenotokous in South Africa, whereas it is thelytokous in Europe. Because all asexual organisms seem to be derived from sexual forms, D. collaris may have evolved in South Africa and dispersed to Europe. The large number of indigenous plants from the Brassicaceae, the richness and diversity of the fauna of diamondback moth parasitoids and the bisexual form of the parasitoid D. collaris in South Africa suggest that diamondback moth might have originated in southern Africa.

For more information see:

Kfir, R. 1998. Origin of the Diamondback Moth (Lepidoptera: Yponomeutidae). Annals of the Entomological Society of America 91: 164-167.