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Heads up on fusarium head blight

Early flowering is the time to apply a prophylactic fungicide on wheat but first assess the field’s disease risk

It’s time to turn a weather eye on cereal crops for fusarium infections.

Fusarium head blight damaged a lot of Manitoba spring wheat last year and farmers should be assessing this year’s risk from the fungal disease that can cut wheat quality and yield.

Since wheat is most susceptible to fusarium infection at flowering, early flowering is the ideal time to apply a fungicide to help protect wheat against the disease, Anne Kirk, Manitoba Agriculture’s new cereal specialist, said in an interview June 23.

While there’s lots of fusarium inoculum around to potentially infect wheat crops in Manitoba, wheat has to be at right stage to be infected.

The risk varies with the weather, Kirk said. Fusarium needs moist, warm (ideally 25 to 30 C) conditions to get established.

Last week most of Manitoba was moist and cool, resulting in a low to moderate risk.

The Manitoba government issues fusarium maps daily, rating the fusarium risk based on moisture and temperature conditions.

Deciding the right time to apply a fungicide can be tricky, especially if crop staging is uneven, Kirk said.

“Try to get an average,” she said. “Also take into account the moisture conditions. If your wheat is starting to head out but the next few days are going to be fairly dry then maybe take a step back and wait a couple of days until more of it is in flower instead of going too early if it is pretty stagey. Farmers should look at the main stem instead of the tillers.

“If you spray at the time of main stem flower the tillers won’t be that much behind.”

photo: Saskatchewan Ministry of Agriculture

Under good growing conditions wheat flowers three days after heading, she added.

Winds or other things can delay spraying, but there can still benefits from a later application, U.S. research shows, Kirk said.

Unfortunately, spraying before the wheat has headed doesn’t protect the crop against fusarium.

Kirk said last week she had calls from farmers asking if applying a fungicide at the flag leaf stage to protect wheat against leaf diseases would also stop fusarium. It won’t.

“It’s (fungicide) not going to be sticking around in the plant to protect when the head comes out,” she said. “So for fusarium you really want to target flowering.”

Other ways to combat fusarium include variety selection — see Seed Manitoba for disease resistance ratings — and taking steps to encourage even crop development including a higher seeding rate.

Manitoba’s wheat crop varies in maturity. Some early-seeded fields have headed and flowered.

Kirk said she hasn’t had many reports of wheat leaf diseases.

“From my travels in the southwest part of the province I haven’t seen anything yet,” she said.

“I think it is because it was dry for quite a while throughout most of the province until last week. There hasn’t been a good chance to get things going.”

Kirk started as cereal specialist May 28, taking over from Pam de Rocquigny, who left in February to be general manager for the Manitoba Wheat and Barley Growers Association and Manitoba Corn Growers Association.

Kirk was Manitoba Agriculture’s pesticide minor use and regulatory specialist. Before that she worked on the University of Manitoba’s participatory plant breeding project.

About the author

Reporter

Allan Dawson is a reporter with the Manitoba Co-operator based near Miami, Man. Covering agriculture since 1980, Dawson has spent most of his career with the Co-operator except for several years with Farmers’ Independent Weekly and before that a Morden-Winkler area radio station.

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