For the past few years a species of Cylindrocarpon, probably C. destructans, has been identified on roots of bareroot and container-grown seedlings in British Columbia. It was first observed in this province in 1963 at the Campbell River nursery, where it was associated with the nematode Xiphinema bakeri which causes corky root disease. Cylindrocarpon is one of the most common fungi found on plant roots, yet the degree of its pathogenicity on conifer seedlings remains unclear. Likely, it is an important factor when seedlings are predisposed by stress (Figure 24).
In nurseries, Cylindrocarpon occurs on Douglas-fir, Engelmann and white spruce, and occasionally lodgepole pine, white pine, western hemlock, and Sitka spruce. Diseased roots (Figure 25) appear dark brown and stunted, and may be rotted. In the nursery, root infection may cause shoot stunting later in the growing season. Cylindrocarpon root rot may reduce root regeneration capacity or, when damage is minimal, go undetected during seedling grading. Both factors could reduce survival of field-planted seedlings.
Cylindrocarpon occurs in soil as a saprophyte or weak pathogen associated with roots of many herbaceous and woody plants. Mycelial growth plays a major role in the survival of the fungus in soil and its spread to new substrates. Conidiospores and chlamydospores are also produced.
Cylindrocarpon is found in the upper and lower soil horizons, and colonizes roots to a greater extent in the latter because it can grow at low oxygen concentrations. It is considered a pioneer colonizer of young root tips due to its great competitive ability, rapid spore germination and mycelial growth, and physiological features such as its ability to use both inorganic and organic nitrogen. It grows rapidly even at low nutrient concentrations, enabling it to colonize new substrates before other fungi. Cylindrocarpon is common in alkaline soils.
*Because little is known about the life history of C. destructans, a diagram is not included here.
In bareroot nurseries, bare fallowing and disking between crops to expose mycelium, conidiospores, and chlamydospores, is a good practice. Maintaining good drainage and sanitation practices in bareroot and container nurseries helps prevent the problem. In the latter, styroblocks should be sanitized between crops. Preventing seedling stress may alleviate the disease. The effectiveness of fungicide drenches against Cylindrocarpon is not yet known, particularly for British Columbia's conditions.
Booth, C. 1966. The genus Cylindrocarpon. Commonwealth Mycol. Inst., Kew, Surrey, England. Mycol. Papers. No. 104, pp. 34-37.
Kowalski, S. 1982. Role of mycorrhiza and soil fungi in natural regeneration of fir (Abies alba Mill.) in Polish Carpathians and Sudetes. Eur. J. For. Path. 12: 107-112.
Kubikova, J. 1965. Mycoflora synusias on the roots of woody-plants. Rozpr. Cesk. akad. ved rada mat. prir. ved 75-(8): 1-53.
|
Other Fungi |
Insects |
Environmental |
|---|---|---|
|
Drought |
|
Principal, locally grown hosts |
Host age and season when damage appears |
|
Nursery type and location |
|
|
|
|---|---|---|---|---|---|---|
|
Bareroot |
Container |
|||||
|
Age |
Season |
Coastal |
Interior |
Coastal |
Interior |
|
|
Douglas-fir, Engelmann and white spruces, sometimes other species |
1+0 |
All year |
Yes |
Yes |
Yes |
Yes |
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Figure 24. Cylindrocarpon sporulating on the stem of a white spruce seedling.
Figure 25. Cylindrocarpon damage on western hemlock. Nothe the dar, stunted roots.