Cane and leaf rust

Cane and leaf rust is a plant pathogenic fungus whose main host is the blackberry although infection of raspberry has been known, it is rare.

Symptoms
Some blackberry cultivars, especially trailing varieties, are susceptible to cane and leaf rust. Symptoms are first visible as pale yellow pustules (uredinia) that protrude from splits in the bark of fruiting canes. Leaves are infected by spores (urediniospores) that originate from the uredinia and further pustules become visible on the underside of leaves in early summer. Severe infections may cause defoliation. Pale yellow-brown coloured spore case clusters develop on leaves in early autumn.

Symptoms are similar to orange rust, which is a less common but more serious disease. Orange rust will cause small, weak shoots to develop near the base of the plant.

Control
The best method of control is to remove and dispose of fruit canes soon after harvest to reduce inoculum sources in combination with the application of fungicides when growing highly susceptible varieties or when the cane and leaf rust is a known problem.

Organic control methods
Destruction of fruited canes immediately after harvest will reduce incidence of the disease. Spraying with lime sulfur or fixed coppers will also help.