Windy weather puts the brakes on spraying

A delayed spring left less room for pre-seed herbicide. Then the wind picked up

Windy weather puts the brakes on spraying

High winds may have left producers with bigger weeds than they would like.

Winds were enough to cause some sandblasting damage in Manitoba’s young crops in late May and early June. Weather stations in Carman reported wind gusts near or above 50 kilometres an hour in the first two weeks of June, with some days clocking gusts of 70 kilometres an hour.

Why it matters: Spray season turned frustrating for farmers in late May and early June because of too-windy weather.

Those same gusts kept sprayers out of the field, during the critical weed-free period for both yield potential and easy weed control.

“It’s a juggling act for every field to balance between getting that early weed removal and having to deal with the conditions that we’re faced with,” provincial weed specialist Tammy Jones said. “You just can’t force the issue and hope the spray is going down if the wind is going 70 kilometres sideways.”

Producers who were unable to spray have seen advancing weeds. Shepherd’s purse and stinkweed have gone to bloom, Jones noted. Winter annuals are, likewise, beginning to mature. Redroot pigweed has been slightly slower to jump ahead, she noted, although she has seen infestations of large lamb’s quarters plants and wild oats.

Many of those plants become significantly more difficult to beat back once they’ve hit bloom, she noted.

“It’s the same normal weeds that we have,” she said, although she added that weeds were somewhat stymied earlier in the season due to spring conditions. “They may have been a little bit slower to emerge just because we’ve had some interesting weather this spring. It gets really cold and then it gets really hot and then it gets really cold again and I’m not sure that has helped everything develop at a normal pace.”

In the east, excess moisture has also set producers back, including some fields that are currently under water.

A string of storms over the second weekend of June dropped several inches of rain across southeastern Manitoba and, in the RM of Stuartburn, led to a local state of emergency due to flooding. According to the CoCoRaHs precipitation monitoring network, about 7.7 inches of rain fell at Vita June 8-11.

“Getting onto those fields is going to be even more of a challenge and the crop is going to be under stress from that excess moisture, so you’ll want to let them recover a bit before you spray them and add additional stress,” Jones said.

Jones pointed to research that suggests producers might lose half a bushel per day of yield potential by leaving weeds in the field to compete with crop.

At the same time, she said during a Crop Talk webinar June 10, drift incidents do nothing to endear producers to either their neighbours or their community.

Searching for a spray window, an online resource operated by Saskatchewan sprayer specialists Tom Wolf and Jason Deveau, puts an upward wind limit at 20 to 25 kilometres an hour, with proper precautions against drift.

“Precautions,” should be the key point when operating in that upper limit, and should factor into any spray plan when wind is above 15 kilometres an hour, Jones said.

She urged producers to take their nozzle type, fluid pressure, boom height and travel speed into account, as well as relative humidity, risk of inversion and the possibility of a buffer strip to protect anything downwind that should not be sprayed.

In particularly windy conditions, that buffer strip should be three times the width compared to normal spraying weather, she said.

Jones also urged producers to consider how those risk factors might interplay to create unintentional drift damage, or, alternately, how they might be sabotaging the efficacy of their herbicide pass. advises producers to consider the required droplet size when planning out a block of time to spray.

Coarse droplets come with less spray risk, but also limits leaf coverage, creating possible issues with contact herbicides. Therefore, the website argues, products needing a finer droplet should be slotted for the best possible spray conditions.

Maximum boom height, likewise, depends on what kind of nozzle the farmer has, since it should be raised only high enough to provide total overlap between nozzles, Jones said.

Travel speed also could use more attention in Manitoba, Jones said.

“We tend to speed up because we’re trying to get things done quicker, but when you speed up you’re needing to increase your pressure in order to get the appropriate water volume on and increasing the spraying pressure decreases your droplet size, and so then you have more fine droplets that end up hanging in the air for longer, which can result in more chemical moving off target,” she said.

In a recent blog post on, Tom Wolf also warned producers to take distance from the ground into account. Most forecasts measure wind 10 metres off the ground, he noted, arguing that correct wind speed at boom level is 0.67 times the forecasted value. He also urged producers to have their own device to measure wind, since data gathered at a station several kilometres away might not match conditions on the field.

If possible, Wolf urged producers to move sideways into the wind to limit drift, and to know what is downwind of the sprayers, and how it might be impacted by the product being sprayed.

About the author


Alexis Stockford

Alexis Stockford is a journalist and photographer with the Manitoba Co-operator. She previously reported with the Morden Times and was news editor of  campus newspaper, The Omega, at Thompson Rivers University in Kamloops, BC. She grew up on a mixed farm near Miami, Man.



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