The Animal Health Board has issued a warning against releasing diseased possums in Northland to reduce the numbers of the pest there.
The board says it's had anecdotal reports that someone may be trying to spread wobby possum disease in Northland as a population control measure.
Wobby possum disease makes them unco-ordinated and weakens them to the point where they usually die.
But northern co-ordinator Frank Pavitt says introducing possums with that condition also risks spreading bovine tuberculosis to part of the county that's free of the disease.
Possums are one of the main sources of Bovine Tb infection in cattle and deer herds.
Mr Pavitt says trying to reduce possum numbers by spreading wobby possum disease is also misguided, because it's not effective.