Aerial blitz targets mozzies

Spraying began in Marlborough yesterday to contain an infestation of the southern saltmarsh mosquito.

New Zealand Biosecure, the company running the programme, is using a helicopter to spray the larvicide Bti in the Vernon Lagoon area, and another smaller area around the Department of Conservation reserve at the outlet of the Wairau Bar.

Senior health protection officer Al Campbell said the area was not closed, but staff would advise people to stay clear until the spraying was completed.

"Obviously there are safety issues with a helicopter operating in the area, and Bti smells a bit like fish-meal - it is something that you don't want to be coated in."

Another aerial spraying of the same area is planned in two to three weeks to catch the next breeding cycle of the insect - the mosquito lays its eggs above the high-tide mark and they will only hatch after a high tide.

The chemical S-methoprene will also be sprayed by teams on the ground over the next few weeks, to cover smaller areas up to the Wairau diversion.

Both S-methoprene and Bti have undergone full environmental and health impact assessment in New Zealand.

The southern saltmarsh mosquito was discovered in Marlborough early last month after duck-hunters reported being bitten on the opening weekend of the season.

A survey of Marlborough indicated the infestation was limited to the Vernon Lagoon and one small outlying site at Lake Grassmere.

Wairau Hospital medical officer of health Dr Maree Leonard said the southern saltmarsh mosquito carried the Ross River virus and while there was no evidence of the crippling disease in New Zealand, eradicating the mosquito would remove the "link in the chain".

"There is urgency to start the treatment programme because current information indicates that the mosquito population is reasonably well-confined at present, making the treatment more likely to be effective."

The initial spraying programme was completed yesterday.

- NZPA