Zespri is accusing Turners and Growers of trying to divide the kiwifruit industry.
The two companies are involved in a High Court case in which Turners and Growers is challenging Zespri's monopoly of the industry.
Turners and Growers say regulations giving Zespri monopoly control over most export markets are unlawful.
Instead it wants a system in place that allows growers to export alongside the company.
Zespri says 90% of growers are happy with the current collaborative marketing regime and a previous Labour select committee recommended no changes be made.
The hearing is set down until the end of the week.