Biology and host specificity of Apion miniatum (Coleoptera: Apionidae) from Israel, a potential biological control agent for Emex australis and Emex spinosa (Polygonaceae) in Australia

The annual southern African plant, Emex australis (Polygonaceae), is a major weed of crops and pastures in Australia. The only other member of the genus is the Mediterranean species Emex spinosa, which is a comparatively minor weed. Both species are targets for biological control in Australia. Past biological control efforts using two weevil species from South Africa and Morocco have not been successful and this has been attributed to the hot dry summers of the Australian regions infested by the weed. An apionid weevil, Apion miniatum, is known from Europe and West Asia and was discovered on E. spinosa in Israel in hot, dry climates similar to E. australis infested regions of Australia. The larvae tunnel in stems, crowns, and roots and the adults feed on leaves and lay eggs into stems and petioles of E. spinosa. Apion miniatum from Israel was imported into Australia where it was reared on E. australis and host specificity tested on 81 plant species in quarantine. Its host range is restricted to Emex species and some Rumex species including, Rumex conglomeratus, R. crispus, R. pulcher, and R. obtusifolius, species that are also declared targets for biological control in Australia. It was concluded that A. miniatum does not present a risk to economic crops or native Australian flora. Based on the findings summarized within this paper, the Australian regulatory bodies approved the insect’s release within Australia and the inaugural release onto E. australis field populations began in 1998. The insect appears not to have established in Australia despite being selected from a region with extreme summer conditions. The biology of A. miniatum is discussed within this context.