Midge, fusarium control all about timing

SCOTT, Sask. — Farmers who are still spraying fungicides on wheat to control fusarium head blight should be paying close attention to crop staging to ensure the best results.

Lyndon Hicks, a regional crop specialist with Saskatchewan Agriculture, says early flowering is the perfect time for fusarium control in wheat.

“Flowering will begin in the middle of the heads,” Hicks told a Crop Diagnostics School near Scott last week.

“When you start to see anthers in the middle of the heads, that is the perfect timing.”

The window is fairly narrow, he added, usually a few days.

However, with farms getting larger and individual producers covering more acres than ever, hitting that window can be difficult.

“When a farmer has large acres to cover, often they start early and end late,” Hicks said.

“That’s just the way it works with the time required to cover large acres.”

Some producers are tank mixing chemicals in an effort to get one-pass protection against orange blossom wheat midge and fusarium headblight.

One-pass coverage is possible, but the timing will not be ideal for both, Hicks said.

“It’s important to understand that the ideal timing for midge control and fusarium control is different,” he said.

“When you do a single application, you are sacrificing control of one or the other.”

For optimal control, insecticides to control midge should be applied earlier, as soon as the head comes out of the boot and is exposed to the air.

Ideal timing for fusarium is a bit later.

In a normal year, fungicide applications to control fusarium in wheat are usually completed by mid-July.

This year, delayed seeding and later crop staging in some areas has delayed applications.

Similarly, the window for fungicide applications to control sclerotinia in canola has now passed, at least in all but the latest crops.

However, canola producers should be planning ahead by examining their fields before harvest for the presence of canola diseases such as blackleg, sclerotinia and clubroot.

“Knowing what diseases you have at the end of the season is the only way to know how successful your disease management strategies have been this year and what you need to do for 2015 in order to be disease free,” said Canola Council of Canada agronomist Clint Jurke.

“You only get one small window to do this well. Do not let it slip by.”

The three major stem diseases that affect canola — blackleg, clubroot and sclerotinia stem rot — are easy to identify in the weeks before harvest.

Among other symptoms, diseased areas of the field will show premature ripening and excessive lodging.

To scout for blackleg, growers should pull up suspicious plants and slice a cross-section through the stem just below ground level.

Blackened tissue inside the stem is a distinguishing characteristic of blackleg infection.

Blackleg has likely reduced a plant’s yield if more than half the area of the stem’s cross-section is blackened.

Canola plants affected by scler-otinia will usually develop bleached or browned stems as the plant matures.

The plant is likely infected with sclerotinia if the stem shreds apart when it is twisted.

The presence of hard, black sclerotia bodies inside bleached stems are a dead giveaway. They are similar in appearance to mouse droppings.

Clubroot, which is still uncommon in Saskatchewan, is conspicuous by the presence of large galls on the plant’s roots or at the base of the stem.

Plants will have large galls at the base of the stem if above-ground symptoms are evident.

Conditions were ideal for scler-otinia infection this year in many canola growing areas.

Environmental conditions such as frequent rainfall, high humidity, heavy morning dews and ample soil moisture are ideal for sclerotia germination, spore production and spore germination and growth.

Temperatures between 20 and 25 C are conducive to sclerotinia infection.

Jurke said those conditions were common in many parts of Western Canada this summer, which has resulted in a heightened risk of sclerotinia-related yield losses.

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