The affected facilities can continue production and sell tomatoes under strict biosecurity measures.
They say the "real crisis" will be next season.
The best option of the four crops was feijoas because they're frost hardy and easy to manage.
It found "little good evidence" large increases in temporary workers have boosted long-term productivity for the horticulture sector.
Sunny days over the past few months combined with rain in January has led to a bumper crop.
Proposed new rules could lead to more bureaucracy and costs for the sector, writes Derek Broadmore of Organics Aotearoa New Zealand.
The company wants to take over OPAC.
"It's very disappointing for growers when we've got a fantastic crop on the trees."
Researchers found having more native plants near crops could attract insects that help with pollination and combat some harmful pests.