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Brown girdling root rot is the most serious disease of canola in the B.C.
Peace. It is caused primarily by the fungus Rhizoctonia solani with
secondary infections by Fusarium species. The disease may even occur
in freshly broken fields and on many soil types. It affects all varieties,
although Argentine varieties are more resistant. Infection levels may reach
80 to 100% in some fields, with losses approaching 50%. Average losses over
the whole Peace district are estimated to be in the range 8-18%. Losses are
highest when wet soil conditions occur at early flowering, followed by dry
weather later in the season.
Symptoms:
 Early
symptoms consist of light-brown lesions on the taproot or main lateral roots
well below the soil line. These enlarge and coalesce, become sunken and girdle
the taproot. Only a short taproot stub may be left. Plants ripen prematurely in
the field, often before any seed has been set. Girdled plants are subject to
death from desiccation or uprooting by wind.
Control:
Cultural:
Shallow
seeding reduces root rot. Optimal soil fertility, including balanced levels of
phosphorus, potassium and nitrogen will help to minimize yield losses. Rotate
with cereals for three to four years and control weeds of the mustard family and
volunteer plants to help prevent a build-up of root pathogens in the soilResistant Cultivars:
Polish varieties are generally more susceptible. Use Argentine varieties in
suitable climatic regions, as they are only moderately susceptible. Plant
breeders are making good progress on the development of Polish varieties with
resistance to brown girdling root rot.
Chemical: There is no chemical control available for brown girdling
root rot.
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