A combination of growing immunity to the rabbit-killing haemorrhagic disease (RHD) and a bumper breeding season means rabbit numbers in some parts of Central Otago have returned to levels last seen before RHD arrived 10 years ago.
The warm, dry summer has been ideal breeding conditions for rabbits, but some pest control leaders warn that while winter poisoning with 1080 would be required to lower rabbit numbers, the cost might prove too great for cash-strapped farmers.
The council's director of resource management, Selva Selvarajah, said in an interview that in some traditionally rabbit-prone areas of Central Otago, such as Tarras, Cromwell and Alexandra, rabbit numbers had exceeded the maximum allowed level for the past two or three years.
This had prompted a review of the council's pest management strategy which recommended a lower maximum level, to give the council more teeth and could result in some landowners being served with direction notices, or council directives to reduce rabbit numbers.
"We are likely to serve more direction notices if we believe we have had no co-operation from farmers.
"Staff have been telling us there has been wide co-operation from landowners and [staff] have been reluctant to enforce direction notices, but it is likely that in the future we will come across cases of no control, or a lack of secondary control, and then we are likely to use a notice of direction."
Dr Selvarajah was unable to say what area of the province was heavily infested.
The review of its Pest Management Strategy resulted in the council proposing to lower the maximum allowed level for Otago from three, four and five depending on the district, to three for the whole province, which has been appealed.
On a scale of one (no rabbits) to eight (an extreme population), the current requirement for Cromwell and Tarras was five, four for Alexandra-Bannock-burn, Upper Clutha, Wakatipu basin, Maniototo-Strath Taieri and inland East Otago.
For the rest of the region, it was three.
Dr Selvarajah said some farmers had seized the opportunity provided by the arrival of RHD and the resulting lower numbers to successfully attack the pest through shooting, gassing and warren ripping.
Others had sat back and let RHD control the population, but because rabbits which had developed immunity were not being killed, numbers were growing.
Regional services manager Jeff Donaldson said the virus was still occurring naturally about twice a year, but some farmers had tried to initiate an RHD epidemic by reintroducing virus they had stored in their freezers.
Mr Donaldson said the virus was of poor quality or had been put on bait which was spread around paddocks.
Ultraviolet light kills the virus, which then immunised rabbits when eaten.
He estimated more than 1500 tonnes of carrot was needed for poisoning this winter to tackle the population, but so far just a third of that had been contracted.
At the peak of the rabbit plague more than a decade ago, 3500 tonnes of carrots were spread, both non-toxic pre-feeds followed by bait laced with 1080 poison.
Mr Donaldson said the cost of poisoning had almost doubled in the last decade, from $25 to $50 a ha to $40 to $80 a ha, due to higher fuel and compliance costs, and that was likely to prevent some poison drops this winter.
"There are certainly some properties with parts exceeding the maximum allowed level and others so close they should seriously be looking at doing something," he said.
A lack of planning meant insufficient volumes of carrots were grown resulting in a possible shortage.
Another issue was the growth of lifestyle blocks in Central Otago, and Mr Donaldson said there were some difficulties co-ordinating and getting groups of landowners to agree to a control programme and the use of 1080.
