Effective spraying starts at the top

Dual tip nozzles may be great for fusarium, but planning and timing are more critical than the technology

PORTAGE LA PRAIRIE, Man. — Only 15 percent of the efficacy of a crop protection package depends on application technology and the spray operation itself.

Thinking accounts for the other 85 percent.

In fact, technology and application rank a distant third place on the list of three factors that affect the success of a crop protection package.

This is especially true as farmers install their twin tip nozzles to go after plant diseases this month.

Talking to growers at CanolaPalooza last week, spray specialist Tom Wolf emphasized that it’s easy to be fooled into thinking that correct nozzle selection and set up are the most important factors in a successful application operation.

“Your thought process before you even look at the sprayer is more important. Filling the sprayer is the third stage in the whole operation,” states Wolf, founder of Agrimetrix Research and Training in Saskatoon.

  • Stage 1: scouting and decision-making. Know exactly what and where the problems are and which product is best for the situation. If you can’t do all the scouting yourself, hire a qualified professional.
  • Stage 2: getting the timing right. A day or two one way or the other can be costly. Know exactly when to pull trigger and then do it.
  • Stage 3: the spraying operation. Wolf cautions against depending on the spray operation to pull you through if you haven’t first done the Stage One and Stage Two homework.

“Application technology is important, but really, it’s just tweaking a small portion of what’s available to us. It’s really only the last 15 percent of the total efficacy package. We can put too much value on this third factor.”

Manitoba farmers were quick to adapt twin tip nozzles in the 1990s as a major weapon in their battle to control fusarium head blight. The forward-backward spray pattern of the dual-fan nozzles provided better foliar coverage. As fusarium moved west, so did the use of twin tip nozzles.

While the concept is great, and they are highly effective in zero wind conditions, Wolf says a lot of producers don’t realize the efficacy drops off when the wind picks up. The odds of success diminish with higher boom height because wind speed and travel speed play greater roles.

Wolf used his hand-held four nozzle boom to demonstrate that spraying against a slight breeze with the rear facing nozzle deposited almost no purple spots on the spray sensitive yellow test strips.

“It’s virtually impossible to put product on the target with the rear nozzle if it’s windy. Most of the time, we recommend you spray in a side wind. That’s not always possible because of lay of the land and tramlines, but it may reduce the impact of wind on the backward facing nozzle.

“We can compensate in two other ways. For one thing, the spray must be relatively coarse so the droplets are big enough to resist the force of the wind.

“Boom height is very important. The chances of your spray going where you want it to go increase as you lower your boom because of its proximity to your target. You have to pay close attention to these aspects to make it worthwhile going to the twin angle nozzle.”

Water volume is another factor where the operator cannot cut corners. Wolf says 10 gallons per acre is the absolute minimum when applying fungicides with a ground sprayer.

When canola varieties grew only three or four feet high and didn’t have a dense canopy or big number of flowers, spraying sclerotinia wasn’t as difficult as it is today with tall plants, dense canopy and a large number of flowers.

“So we have to be generous with the water. You can’t go below 10 gallons. We generally recommend 15 gallons. I talked to a Saskatchewan farmer yesterday who uses 20 gallons per acre.

“He says, ‘I’ve got a valuable crop. It has a bad disease. So I’m going to give my fungicide as much help as I can to make sure it does the job. It’s worth it to load up with 20 gallons. If it means an extra bushel or two per acre, then it might be worthwhile.’

“But it does slow you down. That means fewer acres covered per day. If you use a high water volume and you’re filling often, you might spend half or even three quarters of your day filling. And the window with fungicides is always tight, maybe only one or two days.”

The twin tip nozzle concept was developed by a team of engineers and plant pathologists at North Dakota State University about 20 years ago. Their recommendation was to use a fine spray and go slow.

“We realized the ‘go slow’ part of the equation just wasn’t going to fly in Canada, so we took their idea and got it to work with coarser sprays at higher speeds.”

Wolf recalls how it unfolded. He phoned the researchers at North Dakota State University and they told him what they were doing and how they were doing it. So to test the concept, Wolf and his dad gathered a bunch of parts and built some twin tip nozzles for their own farm near Brunkild, Man.

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