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Cornell Fruit Resources: Berries

Resources for Commercial Berry Growers

White Pine Blister Rust

Genus species: Cronartium ribicola

Distribution: White pine blister rust (WPBR) has been present throughout NY and the New England states for more than 100 years. Following the eradication efforts in the early 20th century, there was a moratorium on currant planting in the region until the development of immune Ribes varieties toward the end of the 20th century. Because of this immunity, the Ribes planting ban was lifted in NY. Unfortunately, a virulent race of WPBR has emerged in CT and NH. In order to prevent the spread of virulent races, producers need to be mindful of this re-emerging disease concern. Although, WPBR races capable of overcoming the existing immunity have not been observed in NY, currant producers need to scout for and manage this disease to prevent the evolution of virulent WPBR races.

Crops of Concern: Currants.

Potential for Economic Impact: The deregulation of planting restrictions on Ribes in NY was contingent on the planting of blister rust immune varieties. The breakdown of immunity in ‘Titania’, ‘Consort’, and other immune cultivars is disconcerting as this disease may threaten the pine industry and result in planting regulations on Ribes in the state of NY. The disease causes relatively minor loss in productivity to Ribes, but threatens the longevity of the industry from sociopolitical standpoint. Actions need to be taken to prevent the establishment of populations able to overcome Ribes immunity.

Identification: The undersides of leaves will develop small bright orange pustules that burst through the epidermis of the leaf and are composed of powdery orange spores. The pustules later give rise telial horns, which look like tiny (1mm long) strings or spikes. These produce the spores capable of infecting pine.

Monitoring and Management: Scout from bloom to harvests bi-weekly for the presence of uredia (orange pustules).

  • Cultural Management – None developed.
  • Chemical Management – Implement a minimal chemical management plan every season to prevent the establishment of populations able to overcome Ribes immunity. Several fungicides are labeled for use against blister rust on Ribes crops in NY. See listings under specific crops. See listings under specific crops in the Cornell Pest Management Guidelines for Berry Crops.

Additional Resources:

  • Plant Disease 95:1589
  • New York Fruit Quarterly, Volume 22(2) Summer 2014
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