The rabbit problem in Central Otago is as bad as it has ever been in some areas and farmers hope a new method of biological control will give them some respite.
Farmers spoken to by the Otago Daily Times said they were cautiously optimistic about the arrival of K5 - a variant of the Rabbit Haemorrhagic Disease (RHDV1) strain already in New Zealand.
The virus, which would be imported from Australia, still needed to be approved by the Environmental Protection Authority, but would hopefully be released throughout Otago this autumn, the Otago Regional Council announced last week.
Its release will cover an area from Roxburgh through to Wanaka and Queenstown, including the Alexandra, Cromwell, Bannockburn, Tarras, Maniototo and Strath Taieri areas. Parts of coastal Otago will also be included in the campaign, including Balclutha, the Otago Peninsula and Shag Point/Moeraki.
ORC director of environmental monitoring and operations Scott MacLean said the virus was not a "silver bullet", and land occupiers would still need to undertake primary rabbit control as well as follow-up secondary control. A communication and education plan would be developed.
He said some areas of Otago had "high" rabbit numbers.
"Some land occupiers are very good at undertaking their rabbit control programmes but it's fair to say this is not universal."
The ORC will pay $50,000 to cover the cost of the virus, two pre-feed carrot applications and one treated carrot application, and landowners will be asked to provide the labour to distribute the baits.
Farmers this week supported the plan, but urged caution to get the timing, distribution and communication correct.
"You have to make sure the farmers and the landowners are on board and understand their role in it," Manuherikia Valley farmer Gary Kelliher said.
"It's important for them to have ownership of it. If it's well planned, there's a far better chance of getting it right."
Kelliher has a unique perspective of the issue, being a former ORC councillor as well as farming a 600ha sheep and deer farm.
He was part of previous discussions by ORC councillors about the virus, and welcomes it. He spends between $10,000 and $20,000 a year on rabbit control, which includes rabbit shooting, poisoning and rabbit netting.
Kelliher said rabbit populations throughout Central Otago were varied. It was vital the ORC took the lead in rabbit control, but landowners in turn had to work closely with the ORC. It was vital secondary controls were also still maintained after the introduction of the virus.
He warned landowners against taking biological control into their own hands, such as in 1997, when a group of farmers illegally introduced RHDV1 to Central Otago.
"It wasn't the right mix, and we've lived with the consequences ever since."
RHDV1 is still having an impact in some areas, but in other areas rabbits have developed an immunity.
Roxburgh farmer Raymond Gunn said farmers hoped the new virus would cull immune rabbits, and those in "hard to reach" areas such as near waterways.
Rabbits were particularly bad in Millers Flat near the township and Clutha River, where shooting and poisoning could not be done. In some areas in the Teviot Valley, rabbits were "possibly as bad as they've ever been", and as bad as they had been before the release of the RHDV1 virus, Gunn said.
However, at Bendigo Station, near Tarras, rabbit numbers were lower than they had been for some time, owner John Perriam said. He thought a large ferret population in the district was having an impact on the rabbits, and said the ferrets were being monitored and not causing any problems with Tb.
He urged caution with the release of K5. It was important it was released when rabbit numbers were high, and not when they were under control.