Landcare Research - Manaaki Whenua

Landcare-Research -Manaaki Whenua

Three Successes with Sustainable Farming Fund

Three biocontrol projects will receive a much needed boost thanks to success in the Sustainable Farming Fund (SFF) round announced by the Ministry for Primary Industries in March this year. The three successful projects will allow on-going work to continue on biocontrol for wasps (Vespula spp.) and field horsetail (Equisetum arvense), and for a new project to begin against horehound (Marrubium vulgare).

Ronny Groenteman, who led two of the applications, is optimistic that good agents can be found to control wasps. There has been a great deal of background work underway looking at the feasibility of wasp biocontrol following a less than successful attempt in the 1990s.  “This new grant awarded to the Vespula Biocontrol Action Group will enable us to pursue novel biocontrol agents for wasps that have not been used elsewhere, and there will undoubtedly be other wasp-infested nations watching with interest,” said Ronny. The project will build on the work undertaken by Bob Brown, who has collected Sphecophaga parasitoids from the UK, which are expected to be released this year. Unlike the Sphecophaga parasitoids released here during the 1990s, which failed to have much impact, the new collections have been sourced from parts of the native range that our wasps originate from. This means they have the right ‘smell’ to avoid detection and subsequent attack from their hosts, and therefore the potential to be much more damaging. “The new work will concentrate on two parasitic flies Volucella inanis and Leopoldius coronatus which look extremely promising. Fortunately, on his trip to collect Sphecophaga in the UK last year Bob found areas where Volucella were abundant, which provides a fantastic head-start.

Biocontrol of the weed horehound, has already been scoped thanks to our ‘neighbours’ in Australia who successfully introduced two biocontrol agents during the 1990s to help control the weed which affects lucerne crop yield and wool quality. The agents, a plume moth (Wheeleria spilodactylus) which attacks the above ground vegetation, and a clearwing moth (Chamaesphecia mysiniformis) which attacks the roots are providing excellent control of the plant in many parts of Australia but other agents may also have potential. The news was well received by the Horehound Biocontrol Group which is led by Gavin Loxton from Lake Tekapo.  “Herbicides were having a minimal effect and damaging lucerne crops. They were also proving costly to apply partly because of the difficult terrain,” he said.  Concerns have been raised by the NZ Association of Medical Herbalists regarding the impacts of biocontrol agents on wild horehound which is harvested for medicinal purposes. “We are planning to meet with members at their annual meeting in May so that they can share their concerns and learn more about how they can participate in the decision-making process undertaken by the Environmental Protection Authority,” said Ronny.

Biological control of field horsetail has been underway for a while but needed additional funding for the programme to be fully developed.  Field horsetail is widespread but is primarily a problem in the Rangitikei region in the lower North Island and it was the Rangitikei Horsetail Group that was pleased to hear their application for further SFF funds had been successful. Lindsay Smith investigated, under the first tranche of SFF funding, the potential of a weevil sourced from the UK and gained approval to release it.  “The weevil has proven difficult to rear in containment, partly due to the unpredictable time that adults take to emerge from the soil, but we have learnt a lot about its life cycle recently,” said Lindsay. “We have just received another shipment from CABI in the UK and will be aiming to build up the population so that the first field release can be made next spring,” he added. The new funding will support mass rearing and distribution of this weevil.