MPI's reluctance to stop plant movements in the wider area around myrtle rust finds could have "grave impacts" on the chances of successful eradication or containment, jeopardising native trees such as pohutukawa, manuka and rata, as well as the feijoa and honey industries.
Mr Browning did, however, applaud MPI's efforts to get word out to the public through social media, printed material and signs.
Questions that remained to be answered included how many of the finds were from human-transferred contaminated plant material, and how the rust first arrived.
"MPI appears to have concluded that the initial incursion must be the result of a wind event with spores blown over from Australia and landing in hotspots in Aotearoa. While this may be the case, until this has been confirmed beyond any reasonable doubt, MPI must fight this battle to the greatest extent possible," he said.
Entire ecosystems could be affected because many birds, lizards and insects relied on trees such as pohutakawa, manuka, kanuka and ramarama.
As of May 26 the disease had been found at two sites in Kerikeri and one in Taheke, as well as 16 sites in Taranaki and one in the King Country.