Cane and Leaf Rust

Cane and leaf rust occurs on some blackberry cultivars, especially trailing varieties such as olallieberry. The first symptom of cane and leaf rust is lemon yellow pustules (uredinia) that split the bark of the fruiting canes of susceptible blackberries. Spores from these pustules (urediniospores) infect leaves and produce small yellow pustules (uredinia) on the underside of leaves during early summer. Defoliation can occur if infection is severe. Buff-colored telia develop among the uredinia on leaves in early fall.

It is important not to confuse this common blackberry disease with the less common but far more damaging orange rust, which causes plants to produce many small, weak shoots from the base of the plant.