Q: I’m hearing more about aphanomyces. How can I prevent the disease from becoming a problem on my farm?
A: Aphanomyces is a serious soil-borne disease of peas and lentils that is becoming increasingly widespread in Western Canada.
Aphanomyces euteiches is a root rot pathogen that thrives under wet conditions. Symptoms are often first detected in low spots or the perimeter of drowned-out areas; however, whole fields can be affected. Under severe infections, yield losses can be as high as 70 per cent.
If you suspect you may have aphanomyces, early detection is key. Little can be done to control an infection in season, but management strategies can be put into place to prevent severe infections in the future.
Infected plants will appear wilted and yellow. Roots will become mushy and may have a caramel discolouration, but this can be masked by other root rots. The best way to confirm an aphanomyces infection is by submitting a soil or root sample to a lab.
Once aphanomyces is detected, there is no silver bullet for control. There are no foliar fungicides registered for aphanomyces, and work on varietal resistance is ongoing. Seed treatments for aphanomyces are available; however, infection of mature plants can occur well into summer and seed treatments only offer seedling protection.
Long rotations are central to an effective management strategy. The pathogen can survive in the soil for many years without a host, so a six- to eight-year break from susceptible crops is recommended. Cereals and oilseeds, including wheat, barley, oats, canola and soybeans, are non-hosts.
Faba beans, which are partially resistant to aphanomyces, are a good pulse crop option during the six- to eight-year break from peas and lentils. Forage crops should be selected carefully, as some forage legumes are highly susceptible to aphanomyces (e.g. cicer milk vetch) while others are partially resistant (e.g. sanfoin).
Heavy, wet and compacted soils are at the greatest risk for disease development. Effective management strategies include drainage and water management, compaction management and field selection for fast-drain- ing soils. Field selection should also consider history of pulse crops and past observations of root rot presence and severity.
Fields with a history of severe root rots should be avoided. As much as possible, prevent the spread of disease by reducing movement of soil between fields.
As always, crop nutrition is vital. Plants with access to adequate nutrients are less susceptible to disease. Properly inoculating pea and lentil crops gives them the best chance of fixing enough nitrogen to meet their needs. Whenever possible, refer to a recent soil test to ensure all other nutrient requirements are being met.
Stacie Yaremko, CCA, PAg, is a manager of agronomic services for Nutrien Ag Solutions in northern Alberta.