Violet root rot

Helicobasidium mompa

This fungus affects a range of plants, from apple trees to carrots and kūmara. It destroys the roots of trees and can rot your root vegetables.

Why is violet root rot a problem for New Zealand?

Violet root rot would harm many crops, like apples, stone fruit, carrots, potatoes and kūmara. The fungus has significantly damaged apple trees in Japan. Violet root rot also invades native ecosystems. It could damage New Zealand's native bush.

Global distribution of violet root rot

World map showing distribution of violet root rot.

How it could get here

Infected nursery stock might bring root rot to New Zealand. We manage the risk of its arrival through rigorous testing and biosecurity procedures.

Always buy your fruit and vegetable plants from a reputable seller.

Where will I find it?

Root rot grows best in warm and wet conditions. You are most likely to find it in the middle of the growing season.

Watching out for violet root rot

Root vegetables will be covered in purple stringy fungus, like a mat.

In trees, the fungus will rot small roots and cover woody roots with purple stringy fungus. It can sometimes affect other parts of the tree.

If you find violet root rot

Note: This information is a summary of violet root rot's global distribution and potential impacts to New Zealand.

Last reviewed: