Wheat Pete's Word — May 20: Weed Escapes, Spray Timing and Manganese on Wheat


The 2015 planting season is moving right into spraying season, as this week’s update from Wheat Pete includes discussion about early weed control in dry conditions, critical weed-free periods for corn and soybeans, and manganese deficient wheat.

Whether it’s lamb’s quarters, pigweed, ragweed or foxtail, “you name it, it’s out there coming gangbusters,” says Peter Johnson. And with dry weather, there have been questions about needing rain to activate pre-emerge herbicides.

“It looks like those pre-emerge herbicides were an absolute waste and we might as well have not bothered spending the money. That’s absolutely wrong,” he says. “Find a sprayer miss. Where you used the pre-emerge herbicide, even without rainfall activation, you get 50, 60, 70 percent control. You’ll be astounded that you’re still getting that level of control.”

Leave a question or listen to “Wheat Pete’s Word” on the phone — call 1-888-746-3311

That being said, it’s time to begin in-crop weed control in some of the earliest-planted corn, as Johnson explains the critical weed-free period for corn begins at the 3 leaf stage.

“If the corn plant is growing, it actually senses the light that reflects off the soil around it. It can tell the difference in the wavelengths being reflected off of residue or bare dirt versus other green tissue,” he says. “If it senses other green tissue, it will compete for sunlight and stretch as tall as it can. In order to do that, it will grow less roots. Then you get into grain fill and you need the biggest root system.”

For soybeans, the weed-free period should start at around the 1st trifoliate stage, which is often around 20 days after planting. (article continued below)

Going back to the topic of healthy roots in corn, while they’re needed for maximizing yields, they can also be a pain the following year, as Wheat Pete discusses some of the challenges with planting soybeans into fields with seemingly indestructible corn root balls.

“Everybody I talk to is whining about root balls,” he says “I really think we have to re-think what we’re doing in terms of no-till soybeans into those corn stalks…I know we can no-till soys and make it work, but boy, this old standard way is just not as easy as it used to be as we continue to make better root systems on that corn plant.”

Listen to last week’s “Wheat Pete’s Word”

The first cut of alfalfa will also be starting shortly, as Johnson figures for high quality alfalfa feed, some producers will be on the field this weekend and early next week. While alfalfa is earlier than normal, he notes pasture growth is off to a slow start: “I think it comes back to this cold injury we’re seeing on the wheat crop. It affected the pasture grass as well.”

Of course, Wheat Pete talks about wheat — scouting for cereal leaf beetle, which has already been reported in some traditional areas, as well as stripe rust, which has yet to be found in Ontario this year. Without rain, wheat fields in some areas continue to exhibit symptoms of manganese deficiency, so growers should be looking at helping the crop out with manganese sulphate.

Finally, he answers more questions called in to 1-888-746-3311 on the nitrogen/fungicide one-two punch for boosting wheat yields, liquid digestate applied on snow exacerbating winter injury in wheat, packing before or after planting corn, and misperceptions about glyphosate.

And that’s it for this week! Check back or call in next week for another update from Wheat Pete.

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