Foliar fungus ignores spring weather

Leaf disease can wreck havoc with pulse crops, especially in years when weather is cool and wet.  |  Michael Raine photo

Field work wasn’t finished last fall and recent cold, wet spring has prairie pulse growers wondering how these circumstances will affect the disease situation.

“Most of our pulse diseases are driven by environmental conditions during the growing season, so we still don’t know for sure what to expect this year,” says Saskatchewan Agriculture plant disease specialist Barb Ziesman.

“But if we look back at what we’ve seen over the past few years, there are definitely a few diseases that should already be on our radar. If we’re talking lentils, anthracnose is definitely still the most prevalent disease, along with root rot. When we talk about root rot specifically, then we’re dealing with the root rot complex, which can include fusarium, pythium, avenaceum and aphanomyces.

“Specifically when dealing with aphanomyces, it’s challenging to manage. We’re typically looking at an extended rotation of six to eight years. We don’t have any post-emergent product. There’s seed treatment, but it doesn’t actually relate to any reduction in disease severity at the end of the season,” says Ziesman.

She cautions producers about trying to save a sprayer pass by tank-mixing fungicides with herbicides. Fungicide timing is critical. Trying to do a double spray job puts you either earlier or later than the target day, and can waste that fungicide application. The fungicide application must be timed to the correct disease stage.

“My other major caution is to make sure you follow the label. If you want to do a tank mix, make sure it’s registered. I know there are guys who cut rates early in the season to save money. If you cut the rate, there will be members of the disease population that escape and they will continue to develop as the season progresses.

“Don’t cut rates on fungicides. Also, we recommend using products with two modes of action. They start with Group 11, then add either a Group 7 or a Group 3.”

Sherrilyn Phelps, disease specialist with SaskPulse, says disease is something pulse growers have learned to live with and remain on-guard for, although there are seldom new problems or new products.

“With spring moisture and good growing conditions, disease risk does increase. Growers need to keep monitoring the environment in their fields to determine if they need a fungicide application,” says Phelps.

“Spring conditions don’t normally affect foliar diseases. The cool damp spring impacts root diseases and seed rot and seedling blight. Seed treatments are the only preventive defence. There’s nothing you can do once the seed is in the ground. But there are things you can do once the plants are growing.”

She says it’s too early to see what impact the spring conditions will have on pulse diseases. She says producers don’t typically see foliar diseases until mid-June and July. With foliar diseases, the environment at the moment has greater impact than spring conditions.

“When you try to apply a fungicide and an herbicide in the same operation, you will be off label with one or the other. The application timing for the majority of fungicides is early flower. That is past the registered application date for herbicides.

“Some guys are doing an early application with the herbicide at the right time. But that timing is too early for the most fungicide benefit.”

She says that SaskPulse has developed six individual product sheets, each covering the fungicides available for that specific crop. These Pulse Advisor Newsletters include all fungicide options related to diseases in a particular crop. They include lentils, field peas, chickpeas, fababeans, soybeans and dry beans.

Until now, fungicides for pulses were made up of a Group 11 along with either a Group 7 or a Group 3. Group 7 was always the base, and only one other mode of action was added.

But that has changed, says Alberta Agriculture research scientist Robyne Bowness Davidson.

Syngenta recently introduced a pulse fungicide called Miravis Neo 300, which includes all three modes of action.

In an email, she said Miravis Neo 300 is a multi-action fungicide containing Group 11 azoxystrobin along with Group 7 propiconazole and Group 3 pydiflumetofen. It’s registered for use on field peas, lentils and chickpeas to manage a number of diseases.

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