Spraying Success Takes Careful Planning

It’s the most wonderful time of the year! Well, that may be a stretch, but fungicide application might just be the most important time of the year. And while fungicides may be pricy and tough to get the timing right, they are a critical tool for Canadian farmers.

While disease concerns differ based on location and crop, there are several key factors that Canadian farmers need to think about in order to have spraying success.


Before farmers even pull the sprayer out of the shed, they need to review their field history going back at least one year, perhaps two, says Albert Tenuta, field crop extension pathologist with the Ontario Ministry of Agriculture, Food and Rural Affairs.

“If you have fields with issues such as sclerotinia or white mold, other fields that do not, or other disease issues, you plan accordingly based on previous history, variety and hybrid tolerances,” he says, and adds that farmers must consider previous disease issues in each field individually and consult historic weather patterns as a guide to risk reduction to maximize fungicide investment.

That ties into inoculum levels, gauging spore loads within a field (soil and residues) and the overall importance of scouting throughout the growing season to nail application timing.

It just makes sense. If you know which pathogen may be present, and at what levels, you’ll be better informed of the potential need for fungicides, and scouting will tell you when. “You can do everything right: the right management, the right variety and the right fungicide choice,” says Tenuta. “But if you apply it at the wrong time, you won’t be happy.”


Field history and timing considerations, coupled with genetics, pretty much spell out how the season will play out, says Tenuta. “When we look at varietal resistance or susceptibility, genetics is an important consideration that needs to be done now, way before the season even begins.”

That’s perhaps an obvious suggestion, but Tenuta stresses the importance of information at all levels: local, national and international, as well. Without it, farmers miss a critical pre-planning step. He points to corn tar spot to make his case.

Originating in Mexico but found in Illinois and Indiana by 2015, corn tar spot has steadily expanded into Wisconsin, Minnesota and Michigan. It was inevitable and not surprising that in September 2020 tar spot was found in Ontario.

Tenuta says tar spot overwintered in the province, meaning farmers need to be prepared and add the disease to their future management programs. “It’s important to know what the fungicides you’re looking at can do, what their efficacies are for different diseases,” he says.


Once you are ready to get into the field, one of the biggest considerations is that of water volume to guarantee adequate coverage across the entire plant surface, says Tom Wolf, co-founder, along with Jason Deveau, of Sprayers 101.

“We have to spread the water out over a lot more surface area,” he says. “The most effective way to achieve good droplet density, or good coverage, is to add water.”

This feeds into a direct challenge Wolf has to the belief that fungicides must be applied in smaller droplets to work well. “As long as we have enough water, droplet size shouldn’t matter that much,” he says, adding that research he has reviewed suggests western Canadian cereal, oilseed, and pulse crops have not substantiated the claim that a finer droplet size is superior.

According to Wolf, farmers should use a medium-rated nozzle or coarser, which allows for spraying in both warmer and windier conditions due to a heavier droplet weight, which won’t drift or evaporate. At times a finer spray may be prudent because smaller droplets can still cascade around the canopy’s layers better than larger ones, and reach further in.


Wolf’s biggest consideration, though, is timing. Arguably, it’s the most critical factor to ensure a successful fungicide application. “An average spray at the right time is a lot more effective than an excellent spray at the wrong time. ” He also thinks that low-drift nozzles can be considered a timing tool, and any improvement to the logistics of the spray operation, like tendering and cleaning, pay huge dividends.

Wolf reminds farmers to get to know disease lifecycles. For instance, is it trashborne or not? Does it stay below the canopy line, or will it eventually rise up to flag leaf?

“Understand disease and where it starts,” he warns plainly. “Walk through your fields and look straight down. Can I see the leaves I need to protect? If you can, it’s fairly easy targeting. But if you can’t, okay, now I have a challenge that may require some equipment adjustments.”

Obvious solutions farmers need to examine include slower travel speeds, angled nozzles and, if necessary, a fieldspecific spray density, adds Wolf. These basic principles can apply to common disease problems.

Angled nozzles with a lower boom and coarser spray, which helps ensure a droplet weight sufficient to land on the plant’s surface, deal with fusarium head blight better since the pathogen enters at the head of the plant, or glume. Coarse sprays also work better on sclerotinia in canola since the disease attacks the buds and petals in the upper canopy.

However, a disease like Ascochyta blight in chickpeas requires multiple applications with adequate water volume. On followup applications, the canopy will have filled in and finer sprays will provide deeper penetration.

Finally, Wolf suggests using water sensitive paper, usually available from any farm retailer, to get a better sense of where droplets are actually going. Attach it to a plant with a clip, make a pass and assess afterward. When moisture hits it, the paper turns blue. It’s a simple way to understand how deep your fungicide is reaching the right part of your crop canopy.

“You can see the number and size of drops to be able to go forward with some confidence that the job you think should be done is being done,” he says. “If you have a problem, you may want to change your water volume or travel speed.”

Similarly, Tenuta urges farmers to conduct multiple field assessments to determine spray efficacy. “After you’ve applied it, go in after a week or 10 days, see what’s going on,” he says. “Come back three weeks later and see if it’s progressed or not. Did you get the most out of the fungicide?” FF


Coming soon to a field near you!

Another way to improve efficiency during fungicide season is to consider a recirculating boom, which is becoming available on more machines, even as after-market retrofits.

Simply put, the system has one continuous line where spray solution goes in at one end of the boom, leaves from the opposite end and returns to the spray tank. This prevents dead ends at the end of each boom section that settle and don’t flow back to the main tank. In a recirculating boom, the liquid always moves, ensuring fewer issues at clean out.

Although this is a relatively new idea to North America, Wolf says the market is only getting larger.