The Ministry for Primary Industries does not intend taking any formal action against kiwifruit growers who misused the antibiotic streptomycin, in an effort to reduce the incidence of the PSA vine disease.
In May, Zespri gave the ministry the names of Bay of Plenty growers, who either sprayed the bacteriocide outside the control period last spring or illegally injected it into their vines.
MPI compliance director Dean Baigent said an investigation found that 26 growers had misused streptomycin on 45 orchards under their management.
But none of the potentially affected fruit in the orchards was sold, either in New Zealand or overseas.
Mr Baigent said the ministry recognises that PSA threatens growers' livelihoods and they used streptomycin because they were desperate.
He said MPI has sent all growers concerned a warning letter, and told them they will be prosecuted if there are any further breaches of the Agricultural Compounds and Veterinary Medicines Act.