Researchers forced to brew own pathogen problems

LACOMBE, Alta. — This summer may be too dry for fungi.

It means plant pathologist Kelly Turkington’s research into diseases and fungicides could be stymied this year.

“We were starting to get concerned at the research centre that we weren’t going to have any disease,” he said.

Researchers at Agriculture Canada’s research centre near Lacombe, Alta., screen for diseases such as sclerotinia in canola and fungal pathogens affecting wheat and barley. They may have to create artificial conditions with irrigation to encourage disease if conditions remain hot and dry.

Less plant disease is good news for farmers, but they still need to remain diligent when checking fields be-cause a heavy dew can stimulate pathogen growth.

“You don’t necessarily need rainfall every day, but if you have heavy dew formation at night, that will lead to high humidity in the crop canopy and you will have some leaf wetness and that is enough for many diseases to start cycling,” Turkington said during a canola field day at the centre June 23.

As well, a smattering of scattered showers this spring could still create a risk of sclerotinia in canola during the bloom period.

“If the weather was to turn dry and no moisture and daily highs of 30 C or higher, that shuts things down. It will speed crop development so the canola crop will go from flowering much more rapidly,” he said.

“In terms of cereal leaf diseases, it will slow the development of those diseases down, too. It really depends what happens between now and mid to late July.”

Diseases such as stripe rust in cereals and tan spot or net blotch in barley could also occur. Controlling sclerotinia is all about timing, considering that fungicide needs to go on before lesions appear. However, controlling tan spot and net blotch in wheat and barley has more leeway.

“You can see the disease and as long as it hasn’t started to move up onto the flag leaf or that penultimate leaf or the third leaf from the head, you still have an opportunity to spray a fungicide and get a really good level of control,” Turkington said.

He recommended checking first thing in the morning.

The fungi will not likely appear if the soil surface and crop canopy are dry, but soil surface that is wet by mid afternoon means there is likely enough moisture in the plant canopy to start disease.

Sclerotinia is a fungal pathogen that infects more than 400 plant species and can cause significant yield loss.

Crops are at risk if the following occurs:

  • There was already a history of sclerotinia in the specific field or in adjacent fields.
  • If there was adequate June rain to maintain the soil moisture at near capacity along with moderate temperatures to encourage germination of sclerotina.
  • The soil surface underneath the canola canopy remains wet for most or all of the day.
  • Unsettled conditions in late June and throughout July with frequent showers interspersed with windy days without rain.
  • A crop canopy remains wet throughout the day or at least until late in the afternoon. There is further risk if droplets of moisture are found in leaf axils and bases later in the afternoon.
  • Extensive sticking or clumping of petals in the crop canopy are seen, especially in the leaf axils and bases.

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