Orange Rust on Brambles

Need to know: 

• Two periods of infection: 1) bright orange spores produced on leaves in spring 2) teliospores form on underside of infected leaves 
• Symptoms include leaves deforming and turning yellow. 
• Prevention is key: wild brambles should be removed from planting areas, infected plants should be removed, and weeds should be controlled. 

Overview of rust on brambles

Orange rust fungi Gymnoconia niten on black raspberries and blackberries can be a disastrous disease that can mean the removal of all diseased plants. It is characterized by bright orange spores that form on the undersides of the leaves.

Symptoms of rust on brambles

Early symptoms of rust on brambles include leaves turning yellowing and becoming deformed. New growing canes are noticeable weaker and spindly. 

Signs of rust on brambles

Bright orange spores completely cover the underside of the leaves as the infection takes over the foliage.  

Disease cycle of rust on brambles 

The spores of orange rust do best in cool, wet weather. This disease has two periods of infection. In the spring, the bright orange spores (aeciospores) are produced on the leaves. These spores cause localized infections on the leaves. After this infection, teliospores form on the underside of the infected leaves. These teliospores produce basidiospores, which can cause systemic infections. Systemic infections affect the entire plant and are impossible to remove.

Type of Sample Needed for Diagnosis and Confirmation

The Iowa State University Plant & Insect Diagnostic Clinic can help you to investigate and confirm if you plant has this disease. Please see our website for current forms, fees, and instructions on collecting and packing samples. Contact information for each states diagnostic laboratory for U.S. residents.  If your sample is from outside of Iowa please do not submit it to the Plant & Insect Diagnostic Clinic without contacting us

Management of rust on brambles

After the plant is infected with systemic infections, there is little that can be done. Prevention is key in keeping the plants disease free. Cultural controls are very important to disease control. Wild brambles should be removed from planting areas. Any infected plants should be removed as soon as possible. Controlling weeds and using good pruning techniques can improve air circulation and decrease the leaf wetness that is vital for leaf infection. Fungicides are also available to prevent plants from becoming infected.

Fungicide applications may be avoided by following good Integrated Pest Management practices like those listed in this encyclopedia article. Often, the only preventative application is effective to manage plant diseases. If the problem requires a fungicide, state law requires the user to read and follow all labels accordingly. For more information, read Proper fungicide use.