Natural dispersal of <i>Cotesia rubecula</i> the recently introduced larval parasitoid of <i>Pieris rapae</i> through the South Island

Abstract

The natural dispersal of Cotesia rubecula the important larval parasitoid of Pieris rapae (small white butterfly) was assessed through the South Island over 2 years as part of an SFF project to improve management of foliage pests on forage vegetable and seed brassicas grown in the South Island This parasitoid has dispersed naturally from its initial release sites at Lincoln and Christchurch as far south as Dunedin airport as far north as north Cheviot and inland to Methven and Hanmer Springs However it has failed to establish in Southland and is not present in central Otago or Nelson/Marlborough Seasonal surveys indicate that this parasitoid is well synchronised with its host sometimes parasitising complete cohorts in a cropping area There is also strong evidence that C rubecula is displacing the earlier introduced and much less effective larval parasitoid Cotesia glomerata The hyperparasitoid Baryscapus galactopus is also affecting the new primary parasitoid A new SFF project is supporting the introduction of C rubecula into the Nelson/Marlborough region where its future interaction with C glomerata and possibly its other host Pieris brassicae (great white butterfly) a new incursion into New Zealand will be an interesting study