The insect fauna of four weedy Hieracium (Asteraceae) species in New Zealand

Hieracium pilosella, H. praealtum, H. caespitosum, and H. lepidulum (hawkweeds) are serious weeds of New Zealand grasslands. A programme to develop biological control of hawkweeds with insects and a pathogen began in 1992. It first required a survey of the four weed species to determine the identity and seasonal distribution of insects occurring naturally on them. Seventy-six phytophagous species were recorded, including native and exotic polyphagous and oligophagous insects. Insect species that were widely distributed and numerous on all four plant species included Nysius huttoni and several Rhypodes spp. (Lygaeidae), Carystoterpa fingens and Philaenus spumarius (Cercopidae), Aulacorthum solani, Macrosiphum euphorbiae and Myzus persicae (Aphididae), and Zygina zelandica (Cicadellidae). Different groups of insects reached peak abundance at different times between mid December and mid March. From the damage observed it seems unlikely that insects already present in New Zealand can control the plants. None of the specialised European Hieracium fauna was found.