Weed of the Week: wild oats

Many of the top weed pests in Western Canada are showing resistance to herbicides, according to research led by Agriculture Canada.

Hugh Beckie at Ag Canada’s Saskatoon Research Centre classifies wild oats as one of the 10 worst annual weeds in the temperate agricultural regions of the world.

Research indicates that more than 10 million acres of Western Canada is affected by herbicide resistant weeds, with many of those having wild oats or avena fatua.

Farming practices have created the issue. A reliance on a few chemical products, combined with a move away from tillage, has selected for resistant genetics, and has caused weeds that no longer respond to many products, especially those chemicals with a single mode of action.

Estimates on the financial effect of wild oats on Canadian prairie farmers suggest the pest costs more than $500 million annually in lost crop yields.

One large scale study revealed that more than 20 percent of the fields from which seed samples have been tested contained herbicide resistant wild oats.

In that study, more than 1,000 wild oat samples were submitted for testing over a 10 year period. Group 1 resistance was found in 68 percent, while five percent were both Group 1 and Group 2 resistant.

Other than tillage and adding a forage to the crop rotation, rotating herbicides and using herbicides with multiple modes of action are needed to avoid and correct for resistant pest plants, say agronomists.

The challenge with wild oats is that it often emerges along with the crop and if that crop is a cereal, it can limit herbicide choices.

Despite effective herbicide introductions in the 1970s and 1980s, the pest remains abundant.

The seed can remain viable in the soil for as long as seven years, so tillage of mature plants isn’t recommended.

Using bin-run seed can compound efforts to control the pest. Producers can delay seeding, providing time for them to catch wild oats with spring applications of herbicide ahead of the crop.

Higher seeding rates make fields less hospitable to the plant and post planting, harrowing can be effective at killing newly sprouted oats.

Targeted application of fertilizer in, or near seed rows keeps some of it away from wild oats and makes crops more competitive, squeezing out the weed.

Canola and other herbicide tolerant crops are effective against the pest.

In broadleaf crops, there are several grassy weed herbicides that can be effective, but control often requires application at the right time in the weed’s development.

Reduced tillage keeps wild oats seeds in the seed bank from germination and can significantly cut infestations.

Weed of the Week: wild oats SouthWest Saskatchewan    via The Western Producer http://www.producer.com/2013/06/weed-of-the-week-wild-oats/?utm_source=feedburner&utm_medium=feed&utm_campaign=Feed%3A+westernproducer+%28The+Western+Producer%29

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