Myrtle rust never sleeps

No sign of dreaded disease in Tairawhiti but beekeepers remain vigilant.

No sign of dreaded disease in Tairawhiti but beekeepers remain vigilant.

VIGILANT: The pathogen myrtle rust has not yet reached the East Coast but Gisborne beekeeper and Apiculture New Zealand science and research focus group chairman Barry Foster says there is no room for complacency over the fungal disease that can harm manuka and kanuka.
Picture by Liam Clayton

MANUKA and kanuka are among plants the pathogen myrtle rust can harm but the fungal disease has so far not affected manuka in the wild, says honey producer Comvita.

Nor has myrtle rust reached the East Coast, where the manuka honey industry is developing.

“Myrtle rust has not been found in manuka plants in the wild and so far has been found in plant nurseries and domestic environments, including the one infection found on a manuka plant in a nursery,” says Comvita chief executive Scott Coulter.

Since last month, myrtle rust has been confirmed in Te Puke, Te Kuiti, New Plymouth and a Kerikeri plant nursery.

Severe infestations of the fungal disease can kill affected plants and have long-term impacts on the regeneration of young plants and seedlings.

“Plant nurseries tend to have young plants in warmer and more humid environments than natural sites and are generally more susceptible to fungal infections.”

Although myrtle spore production is stimulated in warmer months, it will slow down in winter. But there is no room for complacency, says Gisborne beekeeper and Apiculture New Zealand science and research focus group chairman Barry Foster.

Optimal temperatures

Studies have indicated temperatures of 15degC to 25degC were required for the rust to complete its lifecycle, otherwise the fungus remained dormant.

“We’re in the middle of winter now, which is not the greatest time for rust growth.

“However, we just don’t know the eventual outcome from the incursion of myrtle rust into New Zealand.”

Overseas the impact of myrtle rust has varied widely from country to country and plant species to species.

Comvita’s Mr Coulter says in Australia, no myrtle rust has been found in the Leptospermum genus, to which manuka belongs, since the fungus was discovered in mainland Australia in 2010 and Tasmania in 2015.

“While it is early days in terms of analysing the effect of myrtle rust on manuka, this information is consistent with what we are seeing here.”

“There has been no impact from myrtle rust on their honey production.”

MANUKA and kanuka are among plants the pathogen myrtle rust can harm but the fungal disease has so far not affected manuka in the wild, says honey producer Comvita.

Nor has myrtle rust reached the East Coast, where the manuka honey industry is developing.

“Myrtle rust has not been found in manuka plants in the wild and so far has been found in plant nurseries and domestic environments, including the one infection found on a manuka plant in a nursery,” says Comvita chief executive Scott Coulter.

Since last month, myrtle rust has been confirmed in Te Puke, Te Kuiti, New Plymouth and a Kerikeri plant nursery.

Severe infestations of the fungal disease can kill affected plants and have long-term impacts on the regeneration of young plants and seedlings.

“Plant nurseries tend to have young plants in warmer and more humid environments than natural sites and are generally more susceptible to fungal infections.”

Although myrtle spore production is stimulated in warmer months, it will slow down in winter. But there is no room for complacency, says Gisborne beekeeper and Apiculture New Zealand science and research focus group chairman Barry Foster.

Optimal temperatures

Studies have indicated temperatures of 15degC to 25degC were required for the rust to complete its lifecycle, otherwise the fungus remained dormant.

“We’re in the middle of winter now, which is not the greatest time for rust growth.

“However, we just don’t know the eventual outcome from the incursion of myrtle rust into New Zealand.”

Overseas the impact of myrtle rust has varied widely from country to country and plant species to species.

Comvita’s Mr Coulter says in Australia, no myrtle rust has been found in the Leptospermum genus, to which manuka belongs, since the fungus was discovered in mainland Australia in 2010 and Tasmania in 2015.

“While it is early days in terms of analysing the effect of myrtle rust on manuka, this information is consistent with what we are seeing here.”

“There has been no impact from myrtle rust on their honey production.”

Symptoms to look out for on myrtle plants are:

■ Bright yellow powdery eruptions on the underside of the leaf (young infection).

■ Bright yellow powdery eruptions on both sides of the leaf (mature infection).

■ Brown/grey rust pustules (older spores) on older lesions.

■ Some leaves may become buckled or twisted and die off.

If you think you have seen myrtle rust on any plant, do not touch it. Touching myrtle rust or trying to collect samples will increase the spread of the disease.

Call the MPI Exotic Pest and Disease Hotline immediately on 0800 80 99 66.

You can also help:

If you have a camera or phone camera, take clear photos, including the whole plant, the whole affected leaf, and a close-up of the spores/affected area of the plant.

Your email address will not be published. Comments will display after being approved by a staff member. Comments may be edited for clarity.