Wheat School: Scouting key to better fungicide decisions

Penn State University plant pathologist Alyssa Collins

Winter is a great time to recalibrate your approach to managing wheat diseases and applying fungicides.

That’s the message Penn State University plant pathologist Alyssa Collins shared with agronomists attending the Ontario Certified Crop Advisors annual meeting earlier this month.

It’s a dormant period for humans and also for fungi and plants, says Collins. “So we get to start from zero and look ahead to what our year is going to be, and remind ourselves what are our major issues in any given crop.” It’s also a good time for growers to identify the periods when the need to be actively scouting so they can gather the field feedback required to make good fungicide decisions.

On this episode of RealAgriculture’s Wheat School, Collins shares tips for growers on how they can fine tune their scouting approach for the coming growing season.

The first thing growers need to ask themselves is when do they need a fungicide? “There are lots of situations where fungicide is not helpful,” says Collins. “If you don’t have a fungal disease, you’re not going to get any benefit from a fungicide. The wheat crop may also be suffering from a fungus that is beyond the reach of a fungicide treatment. When it comes to root rots, for example, we can’t get the fungicide down to the area where it would be effective.”

On the other side of the coin, Collins says it’s also important to know when a fungicide can really help a crop. She stresses the importance of knowing which fungicides are most effective on specific diseases. “That information is readily available and is updated every year. There are situations where we know that the fungal disease causes us enough yield or quality loss that we really do get an economic benefit from a fungicide.” (Story continues after the video.)

Collins says understanding when the wheat crop is vulnerable to disease also helps improve scouting effectiveness. “For instance, winter wheat makes a lot of its yield in its upper leaves and the head, so anything that attacks that is going to have the potential to drive yield down. Also, there are certain diseases where the pathogen can’t really get into the plant, except at certain times of year. Fusarium head blight is an example of something that can only get into the plant through the flowers, so we know that protecting the plant outside of this time doesn’t really help us.”

It’s also important to know your fungus and know what parts of the plant need the most protection.

“The flag leaf is the solar panel for this plant,” stresses Collins. “It’s what absorbs the sun’s energy, turns that into sugars and drives them into your grain. Other really important parts are that grain head itself, that also does photosynthesis, and that second leaf down from the flag leaf. Knowing this, we can target the things that we really want to protect on this plant.”

It’s also important to keep an eye on lower leaves: “If we see disease down there, we know it’s more likely to move to the flag leaf. So early scouting is still important. But early scouting, combined with more meaningful fungicide timing is probably going to save you the most money.”

In the video, Collins hones in on three growth periods to focus on for scouting: “I would say at green up is the first time you want to be out there scouting for disease. Probably a little bit before that for other agronomic considerations like how good is your stand, fertilizer, herbicide, things like that, but for disease it’s right at green up, because that’s when we start to be able to detect things like powdery mildew and other leaf disease issues.”

As the plant approaches the boot stage is another important period for scouting: “That’s when we start to see production of those really critical leaves for wheat,” notes Collins.

The final crop scout should be reserved for ripening. Collins says this look at the crop doesn’t help make fungicide decisions, but it does provide a look to the future. “If growers do see quality issues like smuts and bunts, if there’s a lot of head scab, then that’s something you want to keep in mind if you’re doing seed production, or if you were saving seed to plant on your farm. You could possibly make a fungicide decision for seed treating the next crop.”

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