Orange rust, an infection caused by a fungus called Arthuriomyces peckianus, is considered a serious disease for black raspberries. Red raspberry plants, however, are resistant to infection by orange rust. The disease causes orange blister-shaped masses of spores to appear on the underside of the plant's leaves. The leaves of heavily infected plants will wither and die, while shoots infected with orange rust will be spindly and underdeveloped. Using good cultural practices, orange rust can be prevented from infecting black raspberry plantings.
Plant only healthy stock plants when starting black raspberry production. Obtain plants for this purpose from a reliable source. Plant raspberries in well-draining soil or in raised beds to prevent excessive moisture.
Avoid overhead irrigation of black raspberry plants. Do not over-fertilize and be careful about wounding plants during cultivation practices.
Thin raspberry canes within the bramble annually and keep weeds under control to allow for good air circulation. This assists in preventing spore germination and infection.
Monitor black raspberry plants for any signs of the disease on a regular basis.
Remove and destroy any infected plants as soon as they are detected to prevent the possible spread of orange rust to other healthy plants. Also, remove and destroy any old fruiting canes after harvest.
Destroy any abandoned or wild raspberry brambles that may harbor disease near cultivated crops.
- At this time, there are no effective fungicides that can be used to control orange rust infections.