The rates were voted on by growers in a 2018 referendum.
Without a levy HortNZ would cease to operate. HortNZ’s prime reason for existence is to promote growers’ interests, increase fruit and vegetable consumption, and improve the entire industry's profitability.
Yes, if you buy fruit or vegetables from or sell fruit or vegetables on behalf of growers, you are legally required to deduct the levy from your payment to growers, and pay the levy you have collected to HortNZ.
No, not without the approval of at least 50% of growers in the respective sector, by volume and turnover. This would require holding another referendum.