Wet spring = increased presence of
Aphanomyces root rot in pea and lentil fields
Mid-June is the time to scout for Aphanomyces root rot as it will start showing up 4 – 6 weeks after seeding when rainfall has been plentiful. Finding it early makes it easy to distinguish from later-season Fusarium species that will overtake Aphanomyces symptoms on the roots.
What to look for:
- Stunted plants that are yellowing from the bottom up
- Yellowing patches can be irregular in shape and usually occurring along water draws or field depressions
How to confirm:
- Dig up roots from the soil and look for the honey-brown discolouration of the root system
- The most tell-tale symptom is pinching and browning of the epicotyl (root system above seed attachment) that stops at the green stem
Lentil roots with early infection. Lateral roots have a honey-brown colour and a ‘soft rot’. Infection is just starting to move into the epicotyl in some plants (black arrows).
Pea roots with early infection that has already moved into the epicotyl, note pinching of epicotyl that stops at the green stem (blue arrow). The lateral roots are wiry and honey brown. This is evident in the field without having to wash roots.
If roots are washed, the honey-brown discolouration of the lateral roots becomes more obvious, as does the browning of the epicotyl.
What you can do:
- There are no in-crop management options
- The most important management tool is to make a note of yellowing spots in your field, is it in patches, is it the whole field, are there patterns to the yellowing?
- Keep a record of where the yellowing spots are and sample from those areas the next time you want to plant a pea or lentil in that field
- If you want confirmation that it is Aphanomyces, send a root tissue sample to one of the many testing labs across the Prairies
- Extend your rotations between pea and lentil crops
- Soil test the yellowing spots of those fields in the future before making a decision to plant pea or lentil in that field again
Prepared by: Syama Chatterton, June 18, 2024