Pulse School: Differentiating between aphanomyces and fusarium root rot


Every year, pulse growers are on the lookout for root rots which can wreak havoc on not just the current crop but also have impact on future crop rotation decisions. Aphanomyces and fusarium are the main root rots of concern, and can be tough to distinguish from each other.

In this episode of the Pulse School, Sabine Banniza, professor and strategic research program chair at the University of Saskatchewan, says telling the two root rots apart can be challenging due to the lack of clear symptoms for each. She adds that co-infection rates are prevalent, so it’s possible to see symptoms of both when assessing any root rot damage. There are some tell-tale signs, however, that signal the plant is in less than ideal health.

When it comes to aphanomyces, the first signs will be visible likely from the roadway. Stunted and yellowing plants can be a sure indicator that producers or agronomists should scout for root rot.

“If you then dig up the roots, the classical symptom is that the root system is sort of discoulored and has this honey caramel colour instead of the creamy white that healthy roots have. The root system is usually reduced and very often you also find that these infected roots don’t have nodules,” explains Banniza.

For a fusarium infection, she says the the plants will very often have lesions and dark discolouration just above ground level. If producers have a pure fusarium infection, majority of the disease will first show up in the crown area of the root.

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Wet conditions are the precursor for both of the root rots, however, Banniza says fusarium can adapt in a wider range of conditions.

“It’s not as if your field has to be flooded for aphanomyces to take hold, but generally sort of tendency to more wet conditions. Fusarium has much broader environmental adaptability, so we can even see some fusarium in drier conditions. Fusarium root rot is complex in that while sometimes aphanomyces is maybe the first one, and then even if conditions aren’t perfect with this area, and because the root is already weakened, fusarium goes in there as well,” shares Banniza.

Unfortunately, there is no combatting either aphanomyces or fusarium. The only thing that growers can do if they identify they have an infection is, depending on how wide spread it is, adjust crop rotations to not include lentils or peas as these would be the preferred host for both diseases.

Banniza suggests taking a six to eight year hiatus from those crops to have the inoculum reduce enough where a healthy crop would be probable.

There is ongoing research in the area of root rot, however, Banniza says it will be at least three to four years before we start to see partially resistant pea varieties hit the market, and upwards of six to eight years before the same advancements have been made with lentils.


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