Project reference: 1999-03
New Biological Control Agent for Broom
Project description:
Broom (Cytisus scoparius) is an important weed for forestry in New Zealand, and control costs could be substantially reduced by the implementation of an effective biological control programme. There are a number of broom-feeding insects that occur in Europe, where broom comes from, that have potential as biological control agents. Already two insects, a seed-feeding beetle and a sap-sucking psyllid, have been established in New Zealand as biological control agents, to complement the activity of an accidentally introduced twigmining moth. Work is progressing with safety testing of a leaf-feeding beetle, but it is likely that it will not be approved for release since it may also attack tree lucerne (tagasaste, Chamaecytisus palmensis).
A very promising broom-feeding species that is currently being studied in Europe, and under insect containment conditions in Canberra, Australia, is the gall-forming mite, Aceria genistae. Galls of this mite are common on broom plants in the south of France, and in Spain. Heavy infestations cause severe damage to attacked broom bushes. This is probably one of the most damaging species that occurs on broom in Europe. The mites are extremely small, but many generations are produced during spring and summer, transforming stem buds into rounded hairy galls. Australian researchers have developed methods to rear the gall mite on broom plants in laboratory conditions, and are conducting host-range tests to determine whether mites can develop on other plant species besides broom. So far their results are very encouraging, and galls have developed only on broom plants.
We propose that we work with the Australian researchers to test native New Zealand plants that have not previously been exposed to these gall mites. We will identify up to 20 species of legumes and plants from other families, native to New Zealand, that will have to be tested before permission can be granted to introduce the mite into New Zealand. Material of these plants will be obtained, and sent to Canberra where tests will be carried out in the Australian invertebrate quarantine facility. Results will be assessed, and a report prepared for the Forest Health Collaborative that sets out proposals for the next stage in the importation process.
Research Provider:
Landcare Research
