Orange Rust:  Non-Curable Disease in Brambles

Orange rust of brambles (blackberry and raspberries) is beginning to produce spores across Kentucky. Symptoms are often noticed in early spring when newly formed shoots appear weak and spindly. Once infected, the pathogen spreads throughout the entire plant. While orange rust is unlikely to kill brambles, it reduces vigor significantly and results in lower yields.  Infected plants should be removed to reduce disease spread.

Orange Rust of Brambles Facts

  • New shoots emerge with poor growth in early spring. Leaves may yellow and distort. Orange pustules develop on the undersides of leaves, eventually covering these surfaces (Figure 1). Infected leaves often drop readily. Shoot tips and buds may also be infected.
  • Cracks in infected canes reveal orange spores (Figure 2).
  • Over time, infected plants exhibit poor growth, vigor, and fruit production.
  • Once infected, the disease spreads throughout the plant, and all plant parts become infected.
  • Thorny and thornless blackberries, as well as black and purple raspberries, are susceptible. Red raspberries are not know to be infected.
  • Disease favors cool, moist periods. Infection may occur throughout the growing season, as long as conditions are conducive.
  • Caused by the fungi Gymnoconia nitens and Arthuriomyces peckianus.
  • The pathogens survive winter in infected plant tissues, such as canes and roots.
Figure 1: Orange pustules develop on the undersides of leaves. (Photo: Sandra Jensen, Cornell University, Bugwood.org)

Figure 1: Orange pustules develop on the undersides of leaves. (Photo: Sandra Jensen, Cornell University, Bugwood.org)

Figure 2: Cracks in infected cane may develop, and orange spores soon emerge. (Photo: Yesica Cisneros, Grower-Owensboro, KY)

Figure 2: Cracks in infected cane may develop, and orange spores soon emerge. (Photo: Yesica Cisneros, Grower-Owensboro, KY)

Management Options

  • Remove and destroy all wild blackberries or black raspberries in the vicinity.
  • Insure that new plants are disease-free.
  • Dig out infected plants (including roots) and burn or take off-site, as soon as disease is confirmed.
  • No fungicides are labeled for orange rust on brambles.

Additional Information

  • Orange Rust of Brambles (PPFS-FR-S-06)
  • Fruit, Orchard, and Vineyard Sanitation (PPFS-GEN-05)
  • Backyard Berry Disease Management Using Cultural Practices (with Low Spray, No Spray & Organic Options) (PPFS-FR-S-25)
  • Commercial Midwest Fruit Pest Management Guide (ID-232)

 

By Kim Leonberger, Extension Associate and Nicole Ward Gauthier, Extension Specialist

 

 

Posted in Fruit