ORIGIN OF THE DIAMONDBACK MOTH (LEPIDOPTERA, PLUTELLIDAE)

Diamondback moth Plutella xylostella (L), feeds only on plants belongi ng 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 are a;nd spread with the cultivated brassicas around the world. Twenty-two species of parasitoids and hyperparasitoids have been reared from lar vae and pupae of diamondback moth in South Africa Some are specific an d known only from South Africa, indicating a very long association bet ween parasitoids and the pest in the region. This minimizes the possib ility that the diamondback moth arrived in the region with the cultiva ted brassicas approximate to 300 yr ago. A total of 175 wild plant spe cies in the Brassicaceae have been recorded in South Africa, of which 32 are exotic species. It is likely that diamondback moth evolved on i ndigenous brassicas in the region. Diadromus collaris Gravenhorst (Hym enoptera: Ichneumonidae), which has been widely used in biological con trol projects against diamondback moth, is an abundant pupal parasitoi d of diamondback moth in South Africa D. collaris is arrhe notokous 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 i ndigenous 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.