The owners of Bay of Plenty kiwifruit orchards under quarantine are warned they will not be compensated if they decide to cut infected vines.

Minister of Biosecurity David Carter announced a $50 million assistance package for kiwifruit growers on Thursday.

He says the industry is likely to incur a $25 million loss in earnings next season.

At midday Friday, 51 orchards were confirmed with Psa.

Psa response manager David Yard says MAF is not instructing growers from orchards under notice to cut their vines.

'The decision to prune is one for the growers to take and industry has been advising them on that.”

'But we would like to stress to growers that MAF is not instructing them under the notice so MAF will not be compensating growers under the Biosecurity Act for such actions. It's at their own discretion.”

He told SunLive the number of infected orchards was likely to rise daily but stressed that does not mean the infection is spreading.

'There is a perception by some that MAF is chasing this disease. To the uninformed it would look like this disease is getting away from MAF.”

He says the infection could have been in New Zealand for some time, possibly years, but lay inactive in vines and was only noticed recently because it was stimulated by variants such as weather conditions.

'What we believe we're seeing is that the disease may have been here for a considerable time and actually the new finds are a reflection of the more we look the more we find.”

'Because we have people actively looking now. It's not a case that the disease is spreading.”