What Is Orange Rust

Orange rust is a serious disease of black raspberries and blackberries that is caused by two closely related fungi. Orange rust does not infect red raspberries. Although uncommon in Minnesota, orange rust can cause serious damage when it does happen.

What causes orange rust?

Orange rust does not usually kill plants, but it can significantly reduce vegetative growth and yield. The disease is caused by the fungus Gymnoconia nitens. The orange spores are spread by wind and infect leaves of healthy plants during long periods of leaf wetness provided by rain or dew.

How do you treat orange rust?

Once a plant is infected with orange rust, there is no cure but to dig up and destroy infected plants. It is recommended that no black or purple brambles be planted in the same site for at least four years. Preventative fungal sprays can be used on new plants and the soil around them.