A beekeepers' representative predicts the varroa honey bee mite will spread to most of the South Island in the next year.
Attempts by Biosecurity New Zealand and the bee industry to contain the killer bee parasite in the Nelson and Marlborough regions were abandoned in September 2008 after it was found in hives in North Canterbury.
Southern beekeepers had hoped that movement control lines would keep them free of the mite for some years, avoiding the need for the costly chemical treatments that North Island apiarists have to use to protect their bees.
But the chairman of Federated farmers' bee group, John Hartnell, says varroa is now in its third year and well established in the Nelson region.
Indications are that it is spreading quickly through the Canterbury region after its arrival eight months ago, he says, and isolated pockets of infestation are turning up in south Westland.
By spring he expects varroa mite to be entrenched in Otago and to have spread throughout the South Island by autumn next year.
Mr Hartnell says South Island beekeepers will be disadvantaged in coping with the costs of varroa control because they do not have as many opportunities for income from pollination services as their northern counterparts.