About aster yellows phytoplasma
This bacterium is widespread around the world but it hasn't been reported in New Zealand.
It has a large host range recorded, across many different plant families. Hosts overseas include maize, roses, apples, brassicas (like broccoli), gladiolus, clover, citrus, onions, even the hydrangea.
Aster yellows phytoplasma can move into healthy plants by grafting from infected plants. We know some leafhoppers can transfer the bacteria between plants when they feed.
Global distribution of aster yellows phytoplasma
Why this is a problem for New Zealand
Aster yellows phytoplasma causes abnormalities in plant growth. A reduction in the quality and quantity of plant yield would be the main problem if it established here.
Its likely impact in New Zealand would depend on:
- which plants are affected
- whether we have leafhoppers that can carry the bacteria.
At the moment, we don't know whether the insects we have in New Zealand transmit the bacteria.
How it could get here
The most likely way for aster yellows phytoplasma to reach New Zealand is on infected nursery stock or plant material. If an infected insect snuck through the border, it could bring it as well.
Biosecurity New Zealand has strict measures in place to limit the chances of the bacteria or the insect carrier making it through the border.
How to identify aster yellows phytoplasma
The symptoms vary markedly depending on the host plant. And the symptoms aren't unique to aster yellows phytoplasma.
- abnormal growth
- overall stunting
- stems with a 'witch's broom' appearance
- bunchy growth
- yellow leaves
- leaf-like structures instead of flowers (phyllody)
- unusual greening of flowers (virescence).
If you think you've found it
Experienced growers who've found unusual symptoms that match this disease should:
- photograph the plant
- call 0800 80 99 66
Note: This information is a summary of this pest's global distribution and potential impacts to New Zealand.