Oat Crown and Leaf Rust Alert
In oats, crown (leaf) rust is dependent on European buckthorn as the alternate
host and the disease is often serious and substantial losses can occur,
especially in Central and Eastern Ontario. The pathogen is not seed or
soil-borne and European buckthorn is the primary local source of spores
while another source of spores is blown in from the southern US. This
spring buckthorn infection (spore production- aecia) is high in many parts
of the province and is the important spore source therefore oat producers
should be on the alert for crown rust.
There are different races of the fungus and like other rusts they change
over time which can affect a varieties performance over time. Crown rust
is most problematic when the disease develops early and although the weather
conditions have not been ideal to date (mild to warm (15-25°C) during
the day and mild at nights (10-20°C) with adequate moisture (rains,
frequent dews)) things should become more favourable soon. Temperatures
above 30°C stop infection.
The most distinctive symptom of the disease is the production of orange
pustules (volcanoes called uredinia) on the oat leaves and sheathes. These
pustules can produce thousands of orange-yellow coloured spores which
can spread to other fields or infect adjacent plants.
Management
- Use a tolerant variety. Varieties differ in their susceptibility to
the disease and since new rust races develop, this can reduce a varieties
tolerance levels Refer to the Ontario Performance Trials for Spring
Cereal Crops for specific details.
- Plant as early as possible in the spring which may allow the plants
to escape the disease from late season infection.
- Foliar fungicides are affective against the disease but they must
be applied in a timely manner and close to flag leaf emergence in order
to protect the flag leaf. For fungicide recommendations, refer to OMAFRA
Publication 812, Field Crop Protection Guide.
