Attempted new association biological control of Dicranosterna semipunctata Chapuis (Coleoptera Chrysomelidae Paropsini)

Abstract

The new association theory of biological control predicts that novel enemies may be more effective in controlling pest species than their natural enemies This theory was tested using the egg parasitoid Enoggera nassaui Girault (Hymenoptera Pteromalidae) on the Acacia tortoise beetle Dicranosterna semipunctata (Chapuis) (Coleoptera Chrysomelidae) in New Zealand In no choice laboratory bioassays parasitism on the new host was significantly lower than on a natural host Paropsis charybdis Stål (Coleoptera Chrysomelidae) (57 cf 89 eggs/h P002) The fecundity and oviposition rate of D semipunctata were approximately half that of P charybdis A field release of 1500 E nassaui directed against D semipunctata did not result in sustained field parasitism It is suspected that E nassaui will not normally encounter D semipunctata because it searches Eucalyptus not Acacia species The ability of biological control agents to locate the target species in the field needs to be considered when evaluating new association biological control