Population Dynamics and Larval Establishment of Sitona discoideus (Coleoptera: curculionidae) in New Zealand Lucerne

First record ofSitona discoideusGyllenhal 1834 (Coleoptera: Curculionidae) on Norfolk Island

“…Both of the S. discoideus specimens from Norfolk Island shared a COI haplotype that was also found in Australia and New Zealand, suggesting that one of these countries was the source of Norfolk Island's population. Sitona discoideus is a strong flier (Goldson et al 1988), and it could have dispersed to Norfolk Island naturally. However, inadvertent human-assisted dispersal seems more likely, since Australia and New Zealand both have regular shipping and airline links with Norfolk Island (www.…”

“…Oviposition usually occurs between April and December in New Zealand and Australia (Wightman 1981). The larvae burrow into the soil where they feed on root nodules, resulting in stunting and yellowing of host plants due to nitrogen deficiency (Wightman 1981;Goldson et al 1988;May 1993).…”

“…34 Based on research in New Zealand (Goldson et al 1988), S. discoideus has potential to reduce legume productivity and persistence in Norfolk Island pastures. A classical biological control programme using the parasitoidMicroctonus aethiopoides Loan 1975 (Hymenoptera: Braconidae) has assisted in suppressing S. discoideus in New Zealand (Goldson et al 1993) and might also be of economic value to Norfolk Island.…”

The value of parasitoids in biological control

“…As discussed above, the effect of parasitism on larval density is not linear due to density dependent mortality (Goldson et al 1988a;. It can be seen in Fig.…”

“…In brief, this species lays a superabundance of eggs, the neonate larvae from which compete for a limited number of nitrogenfixing root nodules (Goldson et al 1988a). The adult weevils are parasitised by Microctonus aethiopoides Loan (Hymenoptera: Braconidae, Euphorinae), which sterilises and eventually kills the weevils (Goldson et al 1990).…”