Q: What is aphanomyces and how should I manage this disease?
A: Aphanomyces is a relatively new root rot disease in pea and lentil crops that is quickly expanding across the Prairies. Aphanomyces root rot is caused by aphanomyces euteiches, a soil-borne plant pathogen.
The symptoms of aphanomyces root rot are yellowing and stunting of shoots, poor root growth, little nodulation and discoloration or browning of the root area.
Stress factors that can increase the risk of aphanomyces root rot infection include: wet conditions, cool temperatures early in the season, shortened crop rotation, heavy textured soils, soil compaction and nutrient deficiency.
Infection can occur at any time in the growing season, however the most important factor is the presence of soil moisture for fungal infection.
To manage aphanomyces, growers can have their soil tested to avoid planting peas and lentils in known aphanomyces-infested fields. In-crop testing of visually infected plants gives the most accurate confirmation of aphanomyces root rot. To test, collect roots and soil from several plants in mid-June to early July. Sample from the top six inches of soil as well as in low spots in the field, then send the samples to your local lab for testing. Ask your local retail for help with in-crop testing.
Further management practices include rotating crops (four to six years) away from susceptible hosts (peas and lentils) in infested fields, and using a seed treatment that targets the root rot complex. Ethaboxam (Intego) is the only product registered for aphanomyces, for early season suppression. It is registered as a solo product but must be used in combination with other seed treatments. Talk to your local retail about seed treatment options.
Hassan Abidi is a manager of agronomic services with Crop Production Services in southwest Saskatchewan.