British‐based search for natural enemies of the clover root weevil, Sitona lepidus in Europe

Abstract

Since the discovery of the clover pest Sitona lepidus (Coleoptera: Curculionidae) in New Zealand in 1996, substantial effort has been made to find suitable biological control agents. In the summer of 2000 about 8600 Sitona lepidus were collected from 15 locations in 11 European countries. The most common parasitoid recovered was Microctonus aethiopoides (Hymenoptera: Braconidae). These parasitoids were used to infect S. lepidus populations that were then forwarded to a quarantine facility in New Zealand. All European‐derived populations of this parasitoid were found to develop readily in both British and New Zealand populations of S. lepidus. This contrasted with the New Zealand ecotype of M. aethiopoides which was unable to develop in S. lepidus. The S. lepidus population obtained from Caen, France was also parasitised by a Perilitus sp. (Hymenoptera: Braconidae) along with Microsoma exiguum (Diptera: Tachinidae). Microsoma exiguum was also reared from weevils collected in Devon along with a single female specimen of Allurus litu‐ratus (Hymenoptera: Braconidae). Of all the species reared out however, only M. aethiopoides could be induced to parasitise S. lepidus in the laboratory. Thirty‐four different isolates of Beauveria bassiana (Balsamo) Vuillemin (Deuteromycotina: Hyphomy‐cetes) strains were collected, some of which were more virulent than New Zealand isolates already tested against adult S. lepidus. Fifteen isolates of the facultative pathogen Serratia Bizio spp. (Enterobac‐teriaceae) were also collected.