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Dry weather weed control in IP soybeans

Weed control in IP soybeans is always a challenge. This year, it was nearly impossible… but not on all farms

Good weed control in Eastern Canada’s identity-preserved soybean fields this year appears to be just as patchy as the spring and summer rains, particularly in southern Ontario and parts of Quebec. Even Roundup Ready beans were slow to canopy in between rescue rains and required more in-season attention than usual.

Then, as crops headed toward harvest, the concern grew even bigger.

“A lot of the chemistries are water activated, so they didn’t activate to a large degree, or they activated late,” says Neil Batchelor, who covers central and southwestern Ontario for Sevita International. “Your old friends, lamb’s quarters, ragweed, and sow thistle, they’re all out there.”

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Close up of a soybean plant
soybean plant

But most worrisome in IP beans, of course, is Eastern black nightshade. “Night­shade that never got picked up to begin with could be fairly advanced. It likes to hide. It really takes that good, earnest scouting program to identify it and get it taken care of,” Batchelor says.

Farther east on the Ontario-Quebec border, where Andrew Hodges farms and works for Ceresco, the abundance of lamb’s quarters is troubling. It seems to him that too much Pinnacle was sold this year to make sense of what he’s seeing in the field. “It was dry, so the plant shuts down and doesn’t absorb as well. Maybe when they sprayed it was too hot?” he muses. “Or is it because of resistance?”

On average, Hodges estimates farmers in this region probably applied 2-1/2 passes of herbicide control. Where producers were chasing grasses, they may have gone over with as many as five passes. “On a year like this, I would say grass is harder to control,” he says.

Still farther east, Hodges’ colleagues tell him Quebec farmers saw the same issues all the way to Saint-Hyacinthe. In the spring, Eragon seemed to work tremendously, but in the fall, it didn’t seem to be holding on against horsetail and does a very poor job on large grass. “I used Fierce on my own soybeans this year and the only issue I had was ragweed escapes on tilled ground,” says Hodges. “On no-tilled ground, I had no escapes.” Trying to get a handle on escapes with Reflex, and a whole lot of water, seemed to be the best thing to do on the tilled ground.

The only IP bean growers who also tilled and still got away with minimum field passes this year seem to be farming on Prince Edward Island, where IP production has been on the rise for the last five years. Harry VandenBroek, of Atlantic Soy Corp in Belle River, says cold weather in June and early July held the crop back at first, but the beans do appear to have capitalized on timely rains. Even though triazine-resistant weeds have found their way to the Island, most growers appear to have had good success using a pre-emergent program this year.

However, VandenBroek credits the weed control to more than fortunate weather conditions. Many of the weed control products he recalls farmers relying on when he worked in Ontario, such as Pursuit, aren’t options for potato growers because of long-lasting soil residues. So farmers on the Island have become avid about crop rotation, growing their beans after potatoes, which often follow hay crops originally under-seeded to cereals.

“When they’re following potatoes, they have pretty good grass control,” VandenBroek explains. Many growers will then apply a product like Valtera, strictly for pre-emerge broadleaf control. If for some reason they do have to go to a post-emerge, they’re most likely to use Basagran + Pinnacle + Assure. “There are some issues here with mustard and goldenrod,” he says.

Where perennial weeds are a recurring issue, and the predominant practice is conventional or minimum tillage as it is in P.E.I., Barry Gordon of AgVise, an independent crop consulting company based near Hensall, Ont., strongly recommends controlling weeds in the fall. Gordon scouts for farmers who both till and no till a lot of IP beans and he’s seeing a lot of perennial sow thistle this year.

“We aren’t going to do any good spraying Roundup on a frozen sow thistle plant,” Gordon says, “so I think that it’s critical to just about follow the combine with the sprayer, and maybe put a bit of a cocktail together like Roundup + Banvel + 2,4-D to get perennial weeds under control.”

In a no-till scenario, come back in the spring a week before planting with Roundup and even consider including a broadleaf program, Gordon suggests. “Sometimes when you put that on a week before you plant, there is a better opportunity to get moisture to activate it than there is after you plant.”

When it comes to achieving good weed control, Gordon says it’s been his experience that both no till and any kind of tillage can be a challenge. Getting those perennial weeds out before bringing in a plow can make a big difference, and sometimes he’ll see better control in those fields. “This year my guys who were on conventional tillage and who incorporated their herbicide into soil moisture seemed to have better control,” Gordon observes. “We had some great success with incorporating Boundary and Broad­strike; the only disadvantage is we can’t put Authority in when we incorporate.”

Having said that, Gordon has seen better weed control in a no-till system than conventional tillage many times before. “Conventional tillage will let the soil dry out, and if you don’t get a rain, it takes more water to activate fluffy ground than when you have solid ground,” he says.

Another critical piece of advice in 2016 was to scout 18 to 24 days after plant­ing, no matter how dry it was in the region. “That’s when we seem to have an opportunity to get weeds under control, when they are small and actively growing,” Gordon explains. “If I wait until I see a green patch in a field for escapes, I’m too late.”

Gordon says the cost of poor scouting during this time period is often an infestation of lamb’s quarters because, once they grow beyond an inch-and-a-half tall, it’s a real scramble to get any kind of effective cleanup program.

Scout early, scout often (meaning at least once a week), and seriously consider a third-party agronomy service for IP fields, advises Batchelor. “It’s pretty rare that those kinds of services don’t pay for themselves,” he comments. The professional advisers know which pattern weeds to flag early, allowing the opportunity to head off really prolific ones like ragweed and fleabane, for example. Later on, if they find a little volunteer corn coming up, “well, you pay the grandkids 25 cents an ear,” he chuckles.

Batchelor supports many of the same pearls of wisdom put forward by other agronomists, particularly the importance of adhering to crop rotation and chemistry rotation plans, but he also believes IP bean farmers would be wise to make use of multi-species cover crops as well.

“It makes sense to me in terms of the more variable root structures you have in the soil, and as a strong capture of a greater variety of nutrients that can be retained in the top eight inches,” Batch­elor explains. “There is a lot more work to be done on it, but I can hardly wait to see what comes of that.” Instead of new chemistry, for him it’s easier to get excited about the potential contributions that cover crops can make to weed suppression. “Look at the ‘new’ chemistries that are coming out. Dicamba? How long has Dicamba been around? 2,4-D?”

Gordon, who started his career in the chemistry business, is equally dismayed by the apparent lack of progress in the IP market. But he’s not surprised either. “It’s almost like a new family of chemistry has to come on to the marketplace,” he says. “But there isn’t significant volume to offer a payback for the manufacturing company to bring it out.”

The fact is trying to control a broadleaf in a broadleaf crop will always be challenging using a chemical product, Gordon says. “We don’t have strong products as there are in say, wheat or corn. We never have, probably never will.”

This article was published in the October 2016 issue of the Soybean Guide.

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Amy Petherick

Amy Petherick is a Contributing Editor for Country Guide.

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