Environment

Blackberry rust. Biocontrol agent:
Blackberry Rust

Scientific name:
Phragmidium violaceum

Target weed:
Blackberry
Rubus fruticosis

What does blackberry rust look like?

At any time of year symptoms of blackberry rust may be visible on flower buds, unripe fruit or the green sections of growing cane. It is on the upper surfaces leaves, however, that it is most visible as purple-brown spots 2-3 mm in diameter. Corresponding black or yellow pustules up to 1 mm across are found on the undersides of leaves.

The leaves of heavily affected plants turn yellow in autumn, and may fall from the plant.

How does it spread?

Yellow spores produced from late spring until autumn are spread by the wind. Sticky black spores produced from late summer to winter cling to the leaves until germinating in spring to begin a new cycle of infection.

Where is it established?

Blackberry rust is self-introduced and widespread throughout Northland.

How is it used to best effect?

Slashing plants can increase susceptibility to the rust, although a number of blackberry species are resistant to infection. Moving infected plant material to new sites increases the opportunity for infection.