Thirty-six more cases of myrtle rust fungus have been found in the Bay of Plenty since last month, reaching a total of 210 cases to date.
The majority of the Bay's cases are in the Te Puke and Tauranga region, and the region is now the second-worst affected by myrtle rust in the country behind Taranaki, with 288 confirmed cases.
Close to 90 per cent of the Bay's cases were in Tauranga and the Western Bay, including 33 in Bethlehem, 29 in Tauranga and 45 in Te Puke.
Myrtle rust is a serious fungal disease that affects plants including pōhutukawa, mānuka and rātā.
Ministry for Primary Industries manager of recovery and pest management John Sanson said the majority of the detections in the Bay had been on private land.
The recent weather conditions were likely behind the increased numbers, he said.
Sanson said late summer and autumn were when symptoms were most visible. The spread, location and impact of myrtle rust varied seasonally.
He said the amount of awareness of the disease in the Bay of Plenty was encouraging, with 16 notifications of reported sightings in the last month.
A Western Bay of Plenty District Council spokeswoman said the council and its reserves maintenance contractor were keeping an eye out for symptoms in gardens and reserves.
Pōhutukawa were at risk if the disease continued its rapid spread, and affected trees around harbour edges could impact the coastal environment by loss of shade, loss of food source for bees and loss of visual amenity.
A worker at Grower Direct in Tauranga said staff have had to stop selling most strains of pōhutukawa as they were at such high risk. Staff sprayed their plants regularly as it was all they could do to control the problem.
Bay of Plenty Regional Council biosecurity manager Greg Corbett said Biosecurity NZ has led the response to the outbreak and the council was assisting with surveillance.
Severe infestations could kill plants and have long-term impacts on the regeneration of young native plants and seedlings, which could give pest plants like gorse free rein on hills where mānuka flourished.
Tauranga City Council parks asset co-ordinator and arborist Richie Goldstone said people needed to be vigilant and report any suspected instances of myrtle rust to the ministry.
What to do if you see myrtle rust:
Report anything that looks like myrtle rust to Biosecurity New Zealand on 0800 80 99 66.
Do not attempt to touch the plant as this may aid in the spread of the disease.
Take a clear photo of symptoms and the host plant if possible.
Source: Bay of Plenty Regional Council