Initial Survey Results Southern Saltmarsh Wairau
24 May 2004
Results of initial survey for Southern Saltmarsh in Wairau
The results of work to identify the extent of an infestation of Southern Saltmarsh Mosquito near Blenheim have been provided to the Ministry of Health.
New Zealand Biosecure and Nelson Marlborough Public Health Service staff surveyed the area after complaints by duck shooters at Vernon Lagoon who were attacked by mosquitoes on the first weekend of the season.
Chief Technical Officer (Health) Sally Gilbert said the Southern Saltmarsh Mosquito (SSM) was found in the estuary area south of the Wairau Diversion in the area where the duck shooters were bitten and one small outlying site at Lake Grassmere.
Ms Gilbert said the infestation is estimated to be about 800 hectares. “This is probably an overestimation of the true size of the infestation but we have made some assumptions because some areas could not surveyed as they were dry.”
Once these sites have been inundated with water they will be inspected to see whether they have been infested with SSM.
The area covered by this initial delimitation survey included the Wairau estuary and surrounding hinterland as far north as Rarangi, Port Underwood, Queen Charlotte Sound at sites which include Picton, Waikawa and the Grove Arm, the Havelock Estuary, Linkwater and south as far as the Flaxbourne River mouth.
“With the exception of the one small site at Lake Grassmere and the Wairau estuary all other sites surveyed were found to be clear of the mosquito,” Ms Gilbert said.
With the reporting of the incursion, all other public Health Services throughout New Zealand are surveying the saltmarsh habitat within their regions and the results are that no further sightings of SSM have been made to date. Surveillance is still being completed in some areas.
Ms Gilbert said if necessary treatment could begin at the infestation sites in the next week to ten days to suppress the mosquito while further information can be gathered.
“The Southern Saltmarsh Mosquito Technical Advisory Group will meet in late June or early July to analyse the results of these surveys and to advise the Ministry on a range of options for a long term response strategy.