The Ministry for Primary Industries is stepping up its response to the potentially destructive myrtle rust outbreak with new legal restrictions on nurseries.

MPI says 45 nurseries around the country will now be under legal controls, forcing them to take extra precautions to manage the spread of myrtle rust.

Myrtle rust, which appears as bright yellow or orange powdery patches on leaves of myrtle plants, poses a serious threat to some of our most cherished plant species, including pohutukawa, manuka, feijoa, and rata.

The disease is hard to contain and could cause havoc in the environment.

Severe infections can kill plants.

There are still only two known infections, on neighbouring properties in Kerikeri, and nurseries have been voluntarily following additional hygiene protocols to stop the spread of the fungus.

MPI says the new controls should allow the nurseries to continue their business, while protecting against myrtle rust.