A new rabbit virus introduced to fight plagues of the pest in Otago is taking effect.
Field samples from the Otago Regional Council showed the K5 strain of the rabbit haemorrhagic disease is killing its targets.
Rabbits have been costing Otago farmers thousands of dollars in crop damage and control measures.
The council's Scott MacLean said while it was excellent news, the virus will not be widespread yet.
Mr MacLean said it will continue to spread for 12 to 14 weeks, and land owners should plan secondary controls for winter.
Farmers who are noticing dead rabbits on their property are asked to contact biosecurity officers at the regional council so they can be tested.