Myrtle rust has been found on two properties in the Waikato town of Otorohanga.
MPI says the new infections appear to have been caused by wind dispersal from Australia, and are not related to the first outbreak.
The disease affects myrtle plants, such as pohutukawa, manuka, feijoa and bottlebrush.
MPI says the myrtle rust is generally inactive in colder months, and it's not surprising to see symptoms re-emerge in the spring.
