Lamb's-quarters earns top spot as Ontario's worst weed

Friday, July 8, 2016

by SUSAN MANN

Lamb’s-quarters edged out common ragweed as the peskiest weed in Ontario, according to a University of Guelph, Ridgetown Campus survey.

The 2016 poll picking lamb’s-quarters as Ontario’s worst weed was an update of an earlier survey conducted in 2007, when common ragweed grabbed the top spot.

In addition to lamb’s-quarters, this year’s top five worst weeds included: Canada fleabane, common ragweed, eastern black nightshade and pigweeds. Canada fleabane and lamb’s-quarters were very close in the poll.

The top five worst weeds identified in 2007 included: common ragweed, quack grass, pigweeds, lamb’s-quarters and foxtails.

David Bilyea, research technician at the Ridgetown Campus worked with colleagues Kris McNaughton and Christie Shropshire to conduct the online poll during the winter, spring and summer of the top five most troublesome weeds on Ontario farms. The results were released Thursday at the annual Southwest Diagnostic Day, an event at Ridgetown Campus for growers to learn new crop management skills.

Three hundred people from across Ontario responded to the poll. Bilyea says “the survey is strictly an opinion poll.”

About the level of participation, Bilyea says “you always want more but it was a good sampling.”

Lamb’s-quarters is a common annual weed growing up to six feet tall, according to a university press release. It can adapt to almost any environmental condition and is very competitive with all plants.

Bilyea says one reason lamb’s-quarters was selected as the top worst weed may have been because “it’s so common.” The weed is found in fields producing all types of crops, including grains, oilseeds and horticultural produce and in areas where farmers use all types of management practices, such as conventional tillage or no-till.

“Every grower faces lamb’s-quarters to some degree in their operations, and that may have been why it was picked,” he says. “It’s everywhere. It’s a very competitive weed.”

Bilyea says he was surprised by the results and thought Canada fleabane would grab the top spot.

“It (Canada fleabane) just came out of nowhere in the last few years to be such as major problem, particularly for soybean growers,” he notes. “Canada fleabane has always been around. It’s not like it’s a new type of weed. It’s just a new weed that’s invaded fields.”

Also, in certain parts of the Canada fleabane population, there’s resistance to glyphosate, a key component of many growers’ herbicide program to control weeds, he notes.

The university release says weeds compete with crops for resources, resulting in 10 per cent to 50 per cent crop losses for producers every year.

Halton Region cash crop farmer Peter Lambrick didn’t answer the survey, however, he agrees lamb’s-quarters is tough to control. Lambrick farms 800 acres of corn, soybeans and wheat in the Campbellville area.

“Those little black seeds keep germinating and they’re ready to go for next year,” he says.

Lambrick says another problematic weed for him is Canada fleabane as he’s seeing glyphosate-resistance in that weed.

When his weed-killing program isn’t working as well as he’d like, Lambrick says he mixes up his crop rotation, “being mindful of the weed spectrum that I have.” He also tries to change his chemistry and “sometimes it’s a combination of products that I can use to better control weeds.”

This year, with the dry conditions it has been tough for farmers as the weeds are better at competing for moisture than the crop itself, he says. “This is why we are seeing pressure put on the young crop. It has been so dry the weeds have out-competed the crop for moisture.” BF