About bacterial leaf scorch
This bacterium can infect many host plants. It causes different diseases in different hosts. It affects plants important to New Zealand, like grapes, olives and citrus. The bacterium multiplies and blocks the water transport system in plants. It stops the water getting from the roots to the leaves.
It goes by many names, such as Pierce's disease in grapes, olive quick decline syndrome, and citrus variegated chlorosis.
This bacterium has killed 1,000-year-old olive trees in Italy and initially devastated vineyards in California. Although, it's now managed in California.
Global distribution of bacterial leaf scorch
Why this is a problem for New Zealand
Xylella is one of the most important plant diseases that MPI wants to keep out of New Zealand. It is an invasive bacterial plant disease that is spreading around the world. We regularly find out about new host plants that Xylella can infect.
Overseas, Xylella has caused devastating diseases in crops like grapes, olives and citrus. These are important to New Zealand's economy.
Scientists have found the bacterium in some of our native plants that were growing in California.
How it could get here
Xylella is spread locally by infected insects when they move to a new plant after feeding on a diseased one. It could travel internationally on infected nursery stock. MPI has strict measures in place to limit the chances of infected nursery stock or insects coming through the border.
How to identify bacterial leaf scorch
Scorched leaves are a sign of some other plant diseases already present in New Zealand. Plants infected with Xylella show:
- scorched leaves
- loss of leaves
- stunted shoots
- reduced fruit size
- over time, dieback and death of the plant.
If you think you've found this disease
If you're an experienced grower and have found unusual signs of leaf scorch on host plants:
- photograph your plant
- call 0800 80 99 66
Note: This information is a summary of this disease's global distribution and potential impacts to New Zealand.