The Government has approved the first phase of the response to the new discoveries of the exotic southern saltmarsh
mosquito, on the East Coast near Gisborne, and in two sites in the Hawkes Bay, Mahia and Porangahau, the Minister for
Biosecurity, Marian Hobbs, announced today.
The response, costing an estimated $800,000, will enable ongoing checks of potential breeding sites, as well as an
initial treatment of sites found to contain southern saltmarsh mosquitoes and larvae.
Marian Hobbs said options for the long term response to these mosquitoes in Gisborne, Mahia and Porangahau would depend
on confirming that the mosquito was not more widely established along the East Coast.
"The only way we can determine if that has occurred is by continued surveillance, particularly after heavy rainfall or
high tides, in the Gisborne region and the coastal areas from Cape Kidnappers to Cape Palliser," she added.
The mosquitoes were first identified in Napier in December 1998. They have since been identified through routine
surveillance in a 36-hectare area in
Gisborne, a 35 hectare area in Porangahau and more recently a 30 hectare area at the Maungawhio Lagoon near Mahia on the
East Cape. The mosquito is a
potential vector for Ross River virus disease.
Marian Hobbs said applying control agents was necessary to attempt to stop the spread of this exotic pest.
Two control agents, employed in the Napier eradication programme, are being used. Bacillus thuringiensis israelensis
(Bti), a biological spray, has undergone a full health impact assessment. The spray leaves no long-term residue and has
no other impact on the environment or people. It is not allergenic. The second control agent, s-methoprene, is an insect
growth regulator that stops the mosquito pupae hatching into adults. It has been used extensively overseas to control
mosquitoes. S-methoprene breaks down quickly in the environment and is believed to be environmentally safe for use in
New Zealand. Studies where it has been applied elsewhere in the Hawke's Bay have shown no impact on non-target species.
The sites at which the mosquito has been positively identified are treated directly with (Bti), which is pathogenic to
mosquito and sandfly. This product has been used extensively in control programmes in Australia, Africa, USA and
Germany. There is a well-documented history of environmental safety together with the knowledge that Bti poses little
threat to mammals.
Ms Hobbs said the containment programme in the Porangahau and Mahia areas will include aerial applications over about 35
hectares of coastal marshlands adjacent to the Porangahau estuary, and approximately 30 hectares of wetlands adjacent to
Maungawhio Lagoon.
The applications of control agents are occurring in areas known to contain the mosquito.
The Ministry of Health says mosquitoes are most active around dawn, late afternoon and just after dusk. The possibility
of being bitten can be reduced by screening open doors and windows, using insect sprays or mosquito coils indoors,
wearing long clothing and repellent when outdoors,
The Ministry's website www.moh.govt.nz will provide regular updates on the southern saltmarsh mosquito.
Ends