The horticulture industry fears a decision to ban the controversial pesticide endosulfan could hurt exports.
Use of the chemical will be banned from 16 January, following an extensive review by the Environmental Risk Management Authority.
Endosulfan has been used as an insecticide on a variety of crops including vegetables, berries and citrus fruits.
Horticulture New Zealand had asked the authority to phase out the chemical over five years instead of an immediate ban.
The organisation's chief executive Peter Silcock said the decision gives growers little more than a month to come up with alternatives.
He said that may mean growers can't control insects properly, and the quality would not be up to that required for export markets, and some produce may be so badly affected it will not be saleable at all.
ERMA says phasing out the pesticide was considered undesirable because of risk to the public and the environment.
The pesticide was responsible for losses of exports in recent years after overseas authorities detected traces of it in shipments of New Zealand beef.
Sports Turf Institute research coordinator Andrew Mitchell said alternatives to endosulfan can be found, though time is limited.
He said one alternative, carbaryl, is more expensive and not effective as endosulfan as it needs several applications and provides a shorter term control on earthworms.
He said other alternatives include altering the pH of soil.