Western gall rust

Endocronartium harknessii

Western gall rust is a disease caused by a fungus. The disease can stop pine trees growing straight. It's only found in North America.

Why western gall rust is a risk to New Zealand

Gall rust could affect New Zealand's pinewood industry. It grows on types of pine trees that are important to our forestry industry. It spreads easily between pine trees and is difficult to control.

While it can kill a single tree, it generally doesn't kill entire stands of trees. The main problem with western gall rust is the damage it does to growing trees.

Global distribution of western gall rust

World distribution of western gall rust

How could it get here?

It's most likely to get here on infected nursery stock or foliage.

MPI has strict measures to limit the chances of plant diseases making it through the border. If you are travelling to New Zealand from overseas, you must declare any plant material so MPI can check if it's safe. If you don't declare it, you may be fined $400 at the border.

How to identify western gall rust

When a tree is first infected, you can't see any symptoms. After a year, small swellings appear on branches and can grow up to cricket ball size. Generally, they're more the size of a golf ball.

In spring, the swellings burst releasing orange spores. The bursting kills off that part of the tree.

Powdery orange spores covering round swellings on a branch
Galls on a branch covered in orange spores. Image: copyright Andrew Khitsun.

Download a western gall rust fact sheet – Cornell University website

Found orange spores?

If you think you've found western gall rust:


Note: This information is a summary of western gall rust's global distribution and potential impacts on New Zealand.

Last reviewed: