Your Reading List

Variable rate fungicide

Variable rate fungicide is a perfect fit for diseases like sclerotinia in canola, says an agronomist.

“The heavier the canopy, the heavier the risk of disease development that you’ve got, versus the areas of the field where we’ve got variability, where the stand is thinner for different reasons,” says Craig Shand, an agronomist with Farmers Edge at Cremona, Alta.

Shand says there’s not much awareness yet about the benefits of variable rate fungicide. “There would be a very small percentage of canola acres across Canada applying fungicide utilizing a variable rate technology system.”

Variable rate benefits

Variable rate technology allows farmers to control sclerotinia more precisely, Shand explains. More fungicide can be applied to areas with a heavy canopy. Average stands receive a regular fungicide rate, while thin stands receive less or no fungicide.

“One of the biggest things I was really scared about when we started working with this technology was shutting the booms off on a portion of the field. I was scared that we were going to see sclerotinia develop where we did shut the booms off. And I can say after two seasons we haven’t seen that. We’ve seen no disease development in those low-risk areas of the field. What we have seen, though, particularly in 2010 when we had heavy sclerotinia pressure, is parts of the field where we sprayed the higher rate of fungicide, we did not see a late secondary infection of sclerotinia show up,” says Shand. He adds that some farmers who applied conventional fungicide rates had secondary infections in areas with heavy canopies.

According to Shand, variable rate fungicide has environmental benefits, such as overall reductions in spray water and fungicide use. It also makes economic sense.

“The nice thing I like about variable rate fungicide is that it takes some of the risk out of it for the producer as far as helping him control his costs a little bit,” says Shand. After applying variable rate fungicide to 3,300 acres over two growing seasons, he figures the savings added up to $4.86 per acre, compared to conventional application. The savings were due to an 18 per cent drop in fungicide use. Shand adds that these cost savings didn’t include potential yield increases. Shand was only able to collect yield data from one test strip last year, but that strip saw a yield response of 2.5 to 3 bushels per acre. He plans to put together more yield data in the future.

Neil Rathgeber farms near Churchbridge, Sask. He’s been using variable rate technology to apply fungicide to his canola crops since 2009. “The first year we had big savings. The last year it wasn’t so much as a savings, but I think we still got (the fungicide) on in the right spots. It may have cost us the same in the end, with the cost of the imagery, as what it would have cost to put the Proline down right across the board… but we got more fungicide on where we needed it,” says Rathgeber. He adds that he’s been happy with the yield response since he started applying variable rate fungicide and fertilizer.


Shand doesn’t see equipment costs as a barrier to adopting the technology. Most high-clearance sprayers can accommodate variable rate technology already, he explains. Custom applicators are often equipped as well. Farmers Edge uses satellites to take pictures of the crop shortly before spraying. These images are then used to develop zone maps, which help determine the application rates for different field zones.

Rathgeber hasn’t had any issues learning to use the technology, and he says that he could manually override the system to correct any problems.

“As far as ease of use, we’re running a Deere sprayer with a Deere GPS unit. Terry and Justin (Rathgeber’s consultants) put the zones onto the card, and we plug the card into the GPS, switch it the auxiliary, put the right field in, and away you go. It’s really quite simple, actually,” says Rathgeber.

Like conventional application, preparation and agronomics are vital to making sure variable rate application goes smoothly and is effective. Before spray season, Farmers Edge sends out technicians to make sure the GPS and other technology on the sprayer work properly. Field scouting helps agronomists and producers decide whether to spray, and allows them to develop a prescription for each zone.

“Also staging’s really key. You want to ensure fungicide’s being applied at the 20 to 50 per cent bloom stage of the canola crop. And ideally we’d probably want to be in that 20 to 30 per cent stage,” Shand says.

Variable rate fungicide isn’t an economical choice for every cropping system, though. “I’ve had clients who have been interested in pursuing it in a cereal crop, but I guess my honest opinion right now is that, in cereal crops, the disease isn’t really dependent on the crop canopy because the disease is coming off of the previous year’s crop residue. And so you can actually have some pretty serious disease issues, even where the stand isn’t as good. On top of that, the economics of the cereal fungicide, they tend to be reasonably cheap, so it just doesn’t pencil out as nicely as it does with a $20 to $30 per acre canola fungicide application,” says Shand.

Ultimately Rathgeber is confident that variable rate fungicide is the right choice for his canola. “We’ve already booked our fields this year to get the pictures done because it’s a no-brainer. Maybe some people wouldn’t agree that it’s a no-brainer, but to me it makes sense.” †

About the author

Field Editor

Lisa Guenther

Lisa Guenther is field editor for Grainews based at Livelong, Sask. You can follow her on Twitter @LtoG.



Stories from our other publications