Alan
McNab
Professor of Plant Pathology |
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| Peas:
Root Rot Diseases |
Root
Rots are caused by several specific soil fungi. These fungi
cause conspicuously discolored and rotted areas on the main root and
at the base of the stem. It is difficult to distinguish between root
rots caused by these fungi. Several fungi may cause root rot on the
same planr. Specific symptoms, characteristic for some root rots,
are noted below. Diseases are named after the organism that causes
the rot.
These root-rot fungi persist in soil and in residue from diseased
plants. In addition, Ascochyta is seed-borne. Excessive soil moisture,
whether from heavy rainfall or from poor drainage, favors root rots.
Root rots are more likely to develop on weak, slow-growing plants
than on those that are vigorous or more rapid in growth. |
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Aphanomyces
Root Rot caused by the fungus , is characterized by water-soaking,
softening, and slight discoloration of the taproot and lower stems.
Ofte the outer root tissue can be readily slipped from the central
woody root tissue. |
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Fusarium
Root Rot symptoms, caused by the fungus Fusarium solani f.
sp. pisi, appear on the stem below the soil line just above the region
of seed attachment. Affected stem areas turn reddish to dark brown.
Internal woody stem tissue sometimes turns brick red. |
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Rhizoctonia
Root Rot symptoms, caused by the fungus Rhizoctonia solani,
usually begin underground on the stem and on roots. Affected areas
are brown to reddish brown, sunken, and eroded. |
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Ascochyta
Root Rot symptoms, caused by Ascochyta spp. of fugi, begin
as purplish streaks above and below ground on the stem, and particularly
at nodes. Streaks enlarge into dark brownish purple areas which may
girdle the stem and exten deveral inches above the soil surface. |
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