Saskatoon, Saskatchewan, Canada
July 21, 2009
Source:
SaskCanola - Saskatchewan
Canola Development Commission
Canola Research Manager, Pat
Flaten, today confirmed that the retesting of a soil sample from
a randomly-selected field in west-central Saskatchewan, using a
DNA diagnostic test and a canola plant bioassay, has confirmed
trace levels of the clubroot pathogen (Plasmodiophora
brassicae).
The results of the testing undertaken and confirmed by
pathologists from Agriculture and Agri-Food Canada (AAFC) and
staff for the Ministry of Agriculture were provided to
SaskCanola.
"Re-testing of the soil
sample over the past 2 months confirms that it is possible
for the clubroot pathogen to exist in Saskatchewan, even in
the absence of disease symptoms in the field. Therefore, we
want to ensure that proper measures are being taken by the
agricultural community and associated stakeholders to
prevent even trace levels of the pathogen from developing
into a disease issue," Flaten stated.
Confirmation of clubroot requires
observation of disease symptoms in a susceptible crop in
addition to detection of the pathogen's DNA in a plant or soil
sample. In this case, clubroot DNA was detected in the soil
sample, and although clubroot symptoms were not observed in the
crop when it was surveyed, the positive bioassay (canola plants
grown in a sample of the soil in a greenhouse under favourable
disease conditions) indicates that there were viable clubroot
spores in the soil sample tested; however, the spore levels
appeared low.
"Plant pathologists will work together to develop a management
strategy for the affected field," Faye Dokken, Provincial Plant
Disease Specialist with the Ministry of Agriculture stated.
"Recently, clubroot was declared a pest in Saskatchewan under
The Pest Control Act, which will facilitate increased clubroot
surveillance and disease prevention and management in the
province."
Under the right conditions - warm, moist, low pH soils -
infection could take place and lead to disease, which has the
potential to increase the spore levels under each rotation
involving a cruciferous crop or even cruciferous weeds. While it
is possible that the clubroot pathogen may be present in the
soil, with or without causing disease, proper crop rotation will
prevent heavy infestations from developing within a field.
"It is important that farmers scout their crops as they head
into the 2009 harvest. Any unusual wilting, stunting, or
yellowing should be further investigated by pulling up plants
and checking the roots - the characteristic clubroot galls will
appear as swellings and malformations on the roots, cutting off
the plant's ability to take up water and nutrients. Farmers are
also reminded to be vigilant as to their best practices
regarding cleaning of field equipment, in order to prevent
clubroot movement to and within Saskatchewan," Flaten concluded.
"Plant pathologists from AAFC and the Ministry conduct an annual
survey of canola crops in Saskatchewan to identify and quantify
new and common diseases of canola. More intensive surveillance
of canola crops and soil testing for clubroot in the province is
warranted for 2009," Dokken said. "The annual canola disease
survey will be conducted as usual in August, and soil samples
will be tested from an additional 60 fields in 2009." |
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