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
 
Strawberry (Fragaria) -- Black Root Rot Complex
See Also: Apple -- Replant Disease
 
Cause: A complex interaction of many fungi, nematodes, and poor soil characteristics. Organisms or factors involved in one area may not be involved in others. Fungi associated with black root rot symptoms are Rhizoctonia fragariae, Coniothyrium fuckelii, Cylindrocarpon spp., Hainesia lythri, Idriella lunata, Pyrenochaeta sp., and Pythium spp. Research in Oregon in the 1930s and 1940s implicated Rhizoctonia sp., Fusarium spp., and Ramularia spp. with root rot of strawberry. (It is interesting that the authors of the original description of I. lunata note its similarity to Ramularia.) Winter injury to roots also reportedly encourages infection by Fusarium sp. and Cylindrocarpon spp.

Some of these organisms are native soil fungi and survive indefinitely in soil. Root-lesion nematodes are frequently involved in root rot diseases such as black root rot. Consider that residual populations of root-lesion nematodes may be high in soils previously planted in legumes. Plants growing in sterile but saturated soil also will develop a black root rot. In addition, black roots can occur when roots dry out during transplanting.

Symptoms: Symptoms include black discolorations on roots; the entire root or all but the core often darken, look unhealthy, and lack new growth. Foliage is reduced in size, has poor color, and wilts in warm weather. Although many roots rot away completely, they lack the red core discoloration typical of red stele.

Roots turn necrotic and do not function for water or nutrient uptake.

Note the many necrotic roots on this plant.

The roots on the right side are starting to turn necrotic near the crown.
 
Cultural control:

  1. Plant certified stock on well-drained fertile soil adapted to strawberry production.
  2. While planting, keep roots from getting dry, and set plants at the proper depth.
  3. Use long crop rotation in commercial plantings; include grasses and grains in the rotation.
  4. Preplant soil solarization has been helpful in western Oregon. Place clear plastic on rototilled ground, which has been irrigated to near field capacity, from mid-July to mid-September. Use in combination with other techniques.
  5. Do not plant strawberries on land with a recent history of black root rot.
  6. Plants with black root rot do not recover and should not be renovated.
Chemical control: Preplant fumigation.

  1. Basamid G. Avoid application when soil is over 90 F. Do not apply within 3 to 4 feet of growing plants. Do not harvest within one year of application. 24-hr reentry plus ventilation.
  2. Methyl bromide + chloropicrin. Restricted-use pesticide.
  3. Telone C-17 at 27 to 41 gal/A broadcast on mineral soils. Allow 2 to 3 weeks between application and planting or until odor leaves the soil. Do not treat extremely heavy soils. 5-day reentry. Restricted-use pesticide.
  4. Vapam (32.7% metam sodium) at 50 to 100 gal/A. Immediately roll the soil and follow up with tarps or a light watering. May use through an irrigation system. 48-hr reentry and/or while tarps are being removed.
  5. When Aliette (and maybe Fosphite) are used to control red stele, there also apears to be a reduction in root damage from some of the fungi in this complex. This is based only on a few field observations and not published research results.
References:
Miller, P.W. 1948. Studies on the cause of strawberry root rot in Oregon: second report of progress. Plant Disease Reporter 32:309-316.

Wing, K.B., M.P. Pritts, and W.F. Wilcox. 1994. Strawberry black root rot: A review. Advances in Strawberry Research 13:13-19.
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.