Top Crop Manager

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New tools in the fight against resistant weeds in corn

May 5, 2016, Ontario – Over the last eight years, growers in Eastern Canada have faced an alarming and unexpected increase in resistance. Glyphosate-resistant giant ragweed, common ragweed, Canada fleabane and waterhemp are among the weeds surfacing across southern Ontario and Quebec. This upsurge in resistance is radically affecting quality and yield in corn and soybean crops and no field is immune.

“The first glyphosate-resistant weed was identified in 2008 in Ontario. Since then, glyphosate-resistant giant ragweed is now found in the six southwestern counties in Ontario,” says Peter Sikkema, professor of field crop weed management at the University of Guelph, Ridgetown Campus. “It has been identified in Essex, Kent, Lambton, Elgin and Middlesex, as well as Huron counties.”

Glyphosate-resistant Canada fleabane seed is wind dispersed, contributing to its rapid spread across southern Ontario. It is now found in 28 counties from Essex county in the southwest to Glengarry county on the Quebec border.

“Based on our research I really think that it is important that farmers incorporate multiple modes of action, on every acre every year, as part of an overall weed management strategy,” says Sikkema.

To aid in the fight against glyphosate-resistant weeds, BASF has introduced a new herbicide for corn called Armezon PRO. According to the company, it is a pre-mix of Armezon and Frontier Max that provides fast-acting, broad-spectrum residual control of both grass and broadleaf weeds for growers looking for additional modes of action and an excellent resistance management strategy.

“Armezon PRO offers a wide window of application from the one to eight leaf stage,” said Rob Miller, technical development manager, Eastern Canada, BASF, in a press release. “It must be applied with atrazine, but for growers looking for an additional activity on tough to control broadleaf weeds, substituting Marksman for atrazine will provide up to five modes of action in glyphosate-tolerant corn.”

Armezon PRO is also fast acting on conventional corn, tank-mixed with Merge up to the three leaf stage.

“If you go into the field earlier at the one to two leaf stage, there is enhanced residual control with the Marksman tank-mix,” continued Miller.

Marksman in combination with glyphosate can be used from the one to five leaf stage. The use of Marksman provides better activity on perennial weeds, as well as glyphosate-resistant species, such as Canada fleabane, giant and common ragweed and waterhemp.

“I think we can confidently say that there will be additional glyphosate-resistant weeds found in the province in the future and the current glyphosate-resistant weeds will be found over a wider geographic area,” said Sikkema. “I think it’s very important that farmers have a diverse crop rotation to reduce the selection intensity for glyphosate-resistant weeds.”