Weather watching helps avoid herbicide crop injury

University of Guelph weed scientist Dr. Peter Sikkema

Leaf twisting, burning, cupping, or crinkling — those are just some of the signs that a crop may be suffering from herbicide injury.

Why do herbicides cause crop injury? University of Guelph weed researcher Dr. Peter Sikkema says injury causes can be classified into seven basic categories. That list includes extreme weather, unique or variable soil characteristics, application errors, seeding problems, interactions with other herbicides, herbicide residues and sensitive crop hybrids or cultivars.

At the Ontario Agricultural Conference earlier this month, Sikkema shared insights into how injury occurs in each situation, described the tell-tale signs growers should look for and offered tips on how to avoid crop damage.

Not surprising, troublesome weather is the number one challenge for herbicides and causes the most headaches for crop producers.

“I think one of the more common reasons why you get crop injury from soil-applied herbicides is if you have cold, wet weather after application,” says Sikkema. “It delays the time from seeding to emergence, and all that time while that crop is below the ground, it’s taking in herbicide. But it’s not growing actively, and it can’t metabolize the herbicide and that results in accentuated crop injury.”

Weather can also play havoc with post-emergent herbicides.” If you have really hot humid conditions, the cuticle on the leaf surface becomes more fluid or more permeable and you get greater than normal uptake of the herbicide. And it results in crop injury.”

Large temperature swings are another factor that can cause headaches for herbicides. “Let’s say it’s below five degrees Celsius at night, and it goes up to 30 degrees during the day. That’s a really broad temperature swing for plants,” notes Sikkema. “They’re not growing as actively and they can’t metabolize the herbicide as quickly.

Herbicides injury, however, does not always mean significant performance or yield loss — plants do have the ability to bounce back. “It amazes me how severe crop injury can look seven to 10 days after herbicide application or after crop emergence,” says Sikkema. “But if you have really good weather and growing conditions for the remainder of the season, in many situations, the crop will recover with no impact on yield.”

Check out Bernard Tobin’s full interview Peter Sikkema below.

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