Zespri has gone to court alleging at least a $30 million loss from kiwifruit orchards planted in China.
It has told the High Court in Auckland the plants were illegally supplied to China by a grower in New Zealand, and is seeking an award of damages by the court.
The respondent has name suppression.
Zespri said the supply of the plants breached intellectual property rights over the SunGold variety, which had been developed by the company itself, and was a trademarked property.
The supply of the plants to China further breached clauses of the Plant Variety Rights Act.
The company said initial investigations confirmed plantings in China of around 160 hectares but there could be more.
These plantings did not have a material impact on Zespri's current business in China but they represented an infringement of proprietary rights in China, which Zespri took very seriously.
"Our action in bringing this case reflects our strong desire to send a clear message that we will vigourously protect intellectual property for our growers in New Zealand and offshore," Zespri said.
"We are seeking at least $30 million in damages, which has been calculated based on the licence value of SunGold licences in New Zealand and the loss of opportunity for Zespri to licence them in China.
"This reflects the importance we place on defending intellectual property rights for our growers and the $20m annual investment our industry makes in innovation including exploring new cultivars."
It has not yet been decided what legal action if any inside China itself.
The plants in China were discovered in 2016.
SunGold is protected by Zespri copyright, but is grown in other countries, such as Italy and France, under licence.