Media Release
20 May 2002
Two southern saltmarsh mosquitoes found near Whitford
Further searching for Australian southern saltmarsh mosquitoes is underway after two adult mosquitoes were trapped near
Whitford in April, the Ministry of Health announced today.
"The mosquitoes were discovered as part of ongoing surveillance in the area following the detection of larvae and a
subsequent treatment programme earlier this year," said Graeme Gillespie, public health programmes manager.
"If more southern saltmarsh mosquito larvae are discovered, there will be further ground treatment using s-methoprene,
an insect growth regulator that stops the mosquito pupae hatching into adults."
Mr Gillespie said larval sampling has not identified breeding sites.
"Surveys have been repeated and will continue again this month after suitable weather conditions occur when rain or
tides inundate the high marsh areas. Staff will identify potential areas to be surveyed and seek to discover where the
breeding areas are."
Initial treatment began in early March near Clifton Road in Whitford after larvae from the southern saltmarsh mosquito
was discovered as part of the routine surveillance programme.
Three semi-rural creek-side sites covering approximately a hectare in area were treated with s-methoprene
"The Minister for Biosecurity authorised the treatment to limit the spread of this unwanted insect," said Mr Gillespie.
"This enabled a flexible and speedy response from operational staff to deliver an effective treatment programme."
The southern saltmarsh mosquito is a potential vector of the Ross River virus. The mosquito lays its eggs on vegetation
just above the waterline but wetting is vital for the eggs to hatch. High tides, heavy rain and wind that increases the
size of waves can all encourage hatching. The mosquito's natural flight range is estimated at five kilometres.
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For more information contact: Zoe Priestley Media Advisor ph: 04-496-2483 or 025-277 5411
http://www.moh.govt.nz/media.html
BACKGROUND
What is s-methoprene? S-methoprene is an insect growth regulator that stops the mosquito pupae hatching into adults. It
is not a spray and does not drift. Sand granules are coated in the active ingredient. S-methoprene is used against
mosquitoes throughout the world. It has undergone a full health impact assessment in New Zealand. S-methoprene breaks
down quickly in the environment and is believed to be environmentally safe for use in New Zealand. Studies of the impact
on non-target species where it has been applied in the Hawke's Bay have shown no impact.
S-methoprene has been used against mosquitoes throughout the world. It has no long term residual effects. The product is
being used successfully as part of the eradication programme in Hawke's Bay and Tairawhiti. It has undergone a full
environmental and health impact assessment in New Zealand. Studies of its use in Napier have shown no adverse impact on
any animals or insects other than southern saltmarsh mosquitoes.
How can people avoid mosquito bites? There are a number of things people can do to avoid mosquito bites: Wear loose
fitting clothing that covers the skin as much as possible - mosquitoes can bite through tight clothing - and avoid dark
colours which attract mosquitoes. Use an effective insect repellent when outdoors. A repellent that contains the
chemical DEET (diethyl toluamide) or DIMP (dimethyl phthalate) is recommended. Doors and windows can be screened to stop
mosquitoes from getting inside. Aerosol sprays and mosquito coils may be used indoors. Check your home and garden for
areas where mosquitoes can breed, such as garden rubbish or blocked gutters and drains which hold water and ensure that
these are kept dry.
When is surveying effective? It is important initial surveying is completed within 48 hours before any larvae become
pupae. The mosquito life cycle has four stages: The EGGS are laid in water. Southern saltmarsh mosquitos lay their eggs
above the surface of the water and the eggs do not hatch until there is a king tide or heavy rainfall to wet them. The
LARVAE hatch out and swim in water. The larval stage is when the mosquito is easiest to detect and is vulnerable to
eradication measures. The PUPAE is the resting stage between LARVAE and ADULT. The pupa is difficult to detect. The
ADULT is the flying stage of the insects life cycle. Breeding and egg laying occur. An adult female southern saltmarsh
mosquito requires a blood meal before laying eggs.
How much funding is the Government allocating to controlling and eradicating exotic mosquitos in 2002? There has been $2
million approved for spending over the current year as part of a multi-year programme attempting to eradicate the exotic
mosquito in Napier, Gisborne, Mahia and Porangahau and for phase one of a possible eradication programme in the Kaipara
and Mangawhai areas.
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