Early flowering is the time to apply a fungicide to suppress fusarium head blight in winter and spring wheat.
But there are things to consider, including if weather conditions are right for the disease (moist and warm), and if the crop is worth investing in, says Manitoba Agriculture’s field crop pathologist Holly Derksen.
Last week some crops were destroyed or badly damaged by hail, and a lot of winter wheat crops were thin to start with, having suffered winterkill.
The rain that came with it could be the moisture the disease needs, Derksen said in an interview June 15, 2018.
“If the weather is hot and dry the flowering period can be extremely short so you want to be in there while the anthers are still open,” she said. “But also take into consideration the forecast. Is it really hot and dry now, but is there rain in the forecast? Then maybe you do want to delay it a couple of days to try and hit the susceptible stage as well as when the environment is conducive.”
Winter and spring wheat staging varies around the province based on the geography, seeding date and weather.
Some winter wheat was heading last week, Derksen said.
Typically spring wheat flowers in late June or early July.
“With milder temperatures and a little bit of moisture that will make it more average timing,” she said. “But if we get hot and dry again that will progress a lot quicker. If there is some stress from dry conditions your crop will want to hurry through its stages.”
Uneven wheat staging makes it harder to decide when to apply a fungicide.
“This year anything early seeded might be a bit more uneven because of the dry conditions,” Derksen said.
“Stuff planted a bit later probably looks better as far as even staging. Look at the main stem, not the tillers. You’re basically trying to hit as many of them (heads) at the right stage as possible. Make sure you are scouting multiple places in the field so you get a good idea where your field is at.”
It’s not often fields can be split based on staging, although sometimes headlands can be treated separately, she said.
“At this point we don’t recommend going in twice (with a fungicide),” Derksen said. “But I know there are many years when the flowering period just seems to go on and on, and some growers do consider a second application, but that’s a risk growers are willing to take because obviously it’s not cheap to go in twice.”
Manitoba’s daily fusarium head blight risk maps can also help farmers with spraying decisions. Currently the map only takes precipitation and temperature into account and not relative humidity. Both can vary across short distances, so consider that when looking at the maps.
The farmer also has to assess if the crop is in the susceptible flowering stage.
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.