Pacific Northwest 1998 An Online Guide to Plant Disease Control

FactSheets offer superior print quality for the page you are currently viewing. Using Microsoft's Internet Explorer has given best printing results.
Glossary
Guide Home
Search

OSU Extension Office
 
Raspberry -- Root Rot
 
Cause: Root rot is a major disease complex of raspberry in the Pacific Northwest. Many fungi and fungus-like microorganisms associated with cane fruit root rots are associated with strawberry black root rot. Phytophthora fragariae var. rubi causes a typical wet-soil root rot on some red raspberry cultivars throughout the region. Other Phytophthora species also may be involved in wet-soil root rot. These fungus-like microorganism survive as oospores or chlamydospores in plant debris. Spores may be moved long distances in contaminated soil. Spores germinate and produce sporangia and a swimming spore stage called zoospores. These spores are attracted to the fine roots where they attack and begin to rot the root system.

Root-lesion nematodes and dagger nematodes also contribute to raspberry root decline and rot, particularly in northern Washington.

'Canby', 'Comox', 'Qualicum', 'Malahat' and 'Skeena' are very susceptible; 'Amity', 'Chilcotin', 'Nootka', and 'Willamette' are susceptible; and 'Chilliwack', 'Meeker', 'Sumner', and 'Summit' are moderately resistant. Young 'Meeker' plants are very susceptible but mature plants seem to have some field tolerance. No Pacific Northwest red raspberry cultivar is very resistant, although some advanced breeding lines are.

Symptoms: Roots are rotted and lack fibrous roots. After hot, dry periods, older leaves may wither or become bronzed and scorched. Affected leaves flag. Fruit stems usually are shortened and berries, if formed, remain small and often wither before ripening. Once the root system begins deteriorating, new roots may arise from above decayed ones in summer. Plants may appear to recover, but new roots are often weak and lack lateral development. The new roots in turn become infected during cold, wet weather the next fall and winter so that the plant progressively declines and is unproductive.

Rows in foreground (lower area of field) have few raspberry plants. Plants a little further back are wilted and stunted with necrotic leves. Plants in background (near the higher area of field) are much greener and fill the rows.

Leaves may wither or become bronzed and scorched. Affected leaves flag.

Leaves may wither or become bronzed and scorched.

 
Cultural control: Best results occur when several cultural and chemical practices are integrated together.

  1. Use certified planting stock and set out in fertile, deep, well-drained soil (3- to 4-ft water table in winter) that has not grown small fruit (strawberry, raspberry, brambles) for several years.
  2. Keep affected plantings economically productive as long as possible by good cultural and fertilizing practices.
  3. Plant resistant cultivars if available.
  4. Subsoil in alleyways to promote drainage away from plants in winter.
  5. Install drain tiles in field to improve drainage.
  6. Plant in beds raised so that the top of the bed is at least 12 inches above the surrounding soil. Amend soil with gypsum (6 tons/A) before making raised beds and planting.
  7. Slope soil away from plants to the center of the alleyway between rows.
  8. Preplant soil solarization has been helpful in western Washington. Place clear plastic on rototilled ground, irrigated to near field capacity, from mid-July to mid-September. Use in combination with other techniques.
Chemical control: Results are best when several cultural and chemical practices are integrated.

  1. Preplant soil fumigation may be effective for severe root rot but delays onset of the disease for only a few years.
  2. Phytophthora root rot control - Ridomil is more effective than Aliette which is much more effective than nothing. Rotate applications between these materials to help prevent building up resistant populations.
    1. Agri-Fos at 2.5 qt/A. 4-hour reentry.
    2. Aliette WDG at 5 lb/A. Do not apply within 60 days of harvest. Four applications are necessary. Apply to foliage twice in fall: in early September before fall rains, then 3 to 4 weeks later. Apply twice in spring, starting after budbreak when new growth is 1 to 3 inches long, then 3 to 4 weeks later. Also registered in British Columbia. 12-hr reentry.
    3. Fosphite at 1 to 3 quarts/A. Do not use copper products within 20 days of treatment and do not use spray adjuvants. 4-hr reentry.
    4. Phostrol at 2.5 to 5 pint/A. 4-hr reentry.
    5. Ridomil Gold SL at 0.25 pint/1,000 feet of row on the soil surface in a 3-ft band over the row. Apply in fall just before the first rains. It is critical to wash this material into the soil as soon after application as possible. Apply during rain or irrigate immediately after application. Repeat in spring if disease is severe. Do not apply within 45 days of harvest. Only one application a year is allowed in British Columbia between harvest and November 30. Some reduced efficacy has been observed in western Washington. 48-hr reentry.
References:
Bristow, P.R. 1994. Phytophthora root rots of strawberry and red raspberry in the Northwest: now and in the future. Proceedings of the Oregon Horticulture Society 85:117-121.

Wilcox, W.F., Pritts, M.P. and Kelly, M.J. 1999. Integrated control of Phytophthora root rot of red raspberry. Plant Disease. 83:1149-1154.
Content edited by: Jay W. Pscheidt on January 1, 2009
 
Top

In print since 1954 and on the web since 1996. Questions or comments, please contact us.