Reason for Concern:
Yellow rust can be a problem in wet growing seasons. This fungus can infect all succulent, above ground parts of the plant causing reduced vigor and yields.

Identification:
Symptoms first appear as distinct yellow spots on the upper surface of leaves. At first the spots are small, yellow to orange and slightly raised (spermagonia). Next, new yellow to orangish spore bearing structures (aecia) are produced in a ring around these spots. By summer, another yellow spore stage (uredinia) appears on the lower leaf surface. Fruit can die on the cane before maturing if leaves on fruiting laterals are attacked early in the summer. Later the lower leaves turn yellow and drop off. All succulent plant parts are subject to infection, but cane lesions are seldom observed. Infected canes develop lesions that become deep cankers and may break off during pruning. By autumn, black pustules (teliospores) form in the yellow uredinia on the underside of infected leaves.

Life Cycle:
The fungus overwinters on old infected leaves and old cane stubs. It progresses through a series of stages, going from spermagonia to aecia and uredinia and finally to overwintering teliospores.

• WSU Raspberry Manual
  
• Oregon State University Online Plant Disease Manual

• In spring and early summer a yellowish spotting appears on the upper leaf surface.
• At first the spots are y small, yellow to orange and slightly raised (spermagonia)
• The small spermagonia develop into new, yellow to orangish spore bearing structures (aecia) produced in a ring that appears around these spots.
• By summer, another yellow spore stage (uredinia) appears on the lower leaf surface.
• Fruit can die on the cane before maturing if leaves on fruiting laterals are attacked early in the summer.
• By harvest, black overwintering spores (teliospores) appear in the yellow uredinia on the lower leaf surface.
• All succulent plant parts are subject to infection, but cane lesions are seldom observed.

• Cultivate in early spring to cover fallen leaves, old cane stubs, and refuse before new leaves appear, thus eliminating inoculum sources.
• Planting resistant cultivars may be an option in some situations.
• Cultivate in late fall to cover fallen leaves, old cane stubs, and refuse to eliminate inoculum source.
• Remove and burn old fruiting canes as soon after harvest as possible, cutting flush with the ground. Cultivate as soon as weather permits.
• Postpone trellising primocanes until leaves drop off or strip leaves from primocanes before tying.
• Planting resistant cultivars may be an option in some situations.

For information about chemical controls, check with our Pesticide Guide.