How to Manage Pests

Yellow rust—Phragmidium rubi-idaei

Yellow rust occurs mostly on boysenberries and blackberries. Small, yellow, blisterlike pustules appear in spring, first on fruiting canes and then on leaves. Canes dry out and crack, preventing proper ripening of fruit.

Solutions

The fungus that causes yellow rust overwinters on fruiting canes. Prune out and destroy diseased canes before fall rains and apply a fixed copper fungicide. Yellow rust spores are released from leaves and spread by wind in spring. Avoid overhead irrigation. Spray with a fixed copper fungicide in spring when new laterals are leafing out, and again when flowers begin to open.

Yellow rust on raspberry leaves