Kiwifruit marketer Zespri is taking legal action to try to stop the unauthorised production and sale of its gold kiwifruit in China.

Zespri owns the rights to Sun Gold, or G3, and growers in New Zealand pay hundreds of thousands of dollars per hectare to grow it.

A grower took clippings to China and since 2016, the amount being grown there has been increasing - it is now believed there are more gold vines in China than in New Zealand.

In an update sent out to growers this morning, Zespri chief executive Dan Mathieson said a civil case had been filed against two defendants involved with the unauthorised production, sale and marketing of the G3 fruit in China's Intellectual Property Court.

Mathieson said it was a significant step in protecting the investment made by New Zealand producers in developing the licensed kiwifruit varieties - and also for its consumers.

Zespri's latest assessment indicates there are now more 7850 hectares of the lucrative fruit planted in China.

Recent law changes in China strengthened the intellectual property rights of the horticulture sector in China, Mathieson said.

He said changes to its Seed Law last year enabled action to be taken against those selling the fruit - rather than just growing it.

An Industry Advisory Council delegation is planning to visit China in the coming months to better understand the situation from orchard to market.

The case will commence in mid-September.

- Monique Steele/RNZ.