Early-season root rots could be on the rise in areas of the province that had a cool, wet start to seeding.
“In the past few years, we’ve seen a lot of root disease issues, and I would say they’re primarily driven by environment,” said Michael Harding, research scientist with Alberta Agriculture and Rural Development.
“These conditions will slow down germination and emergence and give some of those soil-borne fungi a greater chance to cause problems.”
Early-season disease problems are primarily caused by soil-borne fungi that cause root rots, such as fusarium, rhizoctonia, pythium, and cochliobolus. These fungi are “present everywhere” in the province.
“There’s always something in the soil that could potentially cause some disease on crops that are developing and becoming established,” said Harding. “It’s always something to think about, and it’s always something to watch for.”
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The level of disease pressure from root rots is “situational,” depending largely on crop rotations, soil conditions, seeding management, and weather.
“If the environment is conducive to the disease, we can see lots of problems.”
And each fungus thrives in a different environment.
“You’ve got the triple combination punch of fusarium, pythium, and rhizoctonia,” he said.
“If it’s cool and wet, pythium’s going to have its way. If it’s cool and dry, rhizoctonia is going to fare a little better. If it’s warmer and drier, fusarium may be a bigger problem.”
“You’re probably never going to have a season where you won’t see any of these soil-borne fungi causing problems.”
Symptoms and management
The first thing producers will notice if root rots have taken hold in their field is a lack of emergence or a reduction in stand establishment, said Harding.
“Sometimes you’ll see patchy areas where the emergence just isn’t very good. You could start seeing that any time after the seedlings start coming up out of the ground.”
After that, producers should watch for poor stand establishment and post-emergent yellowing or stunting.
“They’re having a hard time pulling the moisture and nutrients out of the soil because of the attack on the root zone.”
At that point, there’s very little producers can do to manage the disease, he said.
“If the crop is already coming up out of the ground, it’s really too late to do much about what’s there. There’s no product you can apply now that’s going to help your root system recover.”
Managing root rots comes down to “avoidance and prevention,” using good crop rotations, proper seeding depth, high-vigour seed, adequate fertility, and seed treatment.
“Anything you can do to get the crop to come up out of the ground and get that seedling growing quickly will help you to avoid and prevent some of these root rot issues.”
But producers shouldn’t skip scouting just because there are no post-emergent management options for root rots.
“There’s sometimes a tendency to use that as an excuse to not scout, but it is really important to get out there and scout.”
Scouting will show any problems that are emerging and whether management techniques are making the situation better or worse.
“Beginning early and frequently scouting can pay off by helping determine where these problem areas may be in your specific fields,” said Harding.
“It’s good to scout at the beginning of emergence when the crops are coming up so that you can watch the establishment and look for patches that aren’t coming up. You can start to see that very early on.”
Once a problem is identified, producers should consult with an agronomist to determine the likely cause, he said.
“At the early stages of crop development, there’s lots of things that can cause patchiness and stand establishment issues. It’s not just diseases.”
Things such as fertility, soil moisture, salinity, pH, and compaction can cause variation in emergence, making an accurate diagnosis essential for management.
“Every time we see some yellowing or poor stand establishment, it may not be a disease. It may be something else, and we shouldn’t jump to conclusions.”