By Alice McFarlane

Green foxtail widespread across the prairies

Nov 17, 2020 | 5:00 PM

MELFORT, Sask. – Farmers and agronomists keep busy during the growing season keeping an eye on troublesome weeds.

One weed of particular concern is green foxtail. It has been consistently ranked in the top three in all of the Agriculture and Agri-Food Canada weed surveys since the 1970s.

Kaeley Kindrachuk is the crops extension specialist with the Saskatchewan Ministry of Agriculture in Outlook.

She said it is not difficult to control weed, but because herbicide resistance is on the rise, it is becoming increasingly more important to know more about the weed.

Kindrachuk said conditions required for green foxtail to germinate can vary.

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“Green foxtail germinates later in the spring, with peak germination occurring once temperatures have hit 20 to 30 Celsius,” Kindrachuk said. “Since it emerges later, this usually means these weeds may be missed by pre or post emergent herbicide applications.”

Germination rates will decrease if temperatures are lower, but it will still occur. Green foxtail is viable in the soil for up to 33 months, but in optimal conditions can remain viable for up to three years.

Kindrachuk said green foxtail should be controlled at the one to three leaf stage, to minimize yield reductions.

“Early emerging weeds are most competitive. Late emerging weeds do not have as much of an effect on yield but they still produce seeds that enter the weed seed bank,” Kindrachuk said.

Herbicide control options are limited in fields where the green foxtail is resistant to groups one and two herbicides.

In the last Ag Canada weed survey in 2014, 400 fields were surveyed. Of the 104 fields where green foxtail was found, 31 per cent had a herbicide resistant weed population. Group one resistant green foxtail was found in 17 per cent of the fields, and group two resistant green foxtail was found in 15 per cent of the fields. Two fields had group one and two resistant green foxtail. The next weed survey is underway and will be wrapped up in 2021.

Kindrachuk said when seeds are mature in late summer or early fall, they will drop from the panicle to the soil surface. These weeds commonly produce hundreds of seeds per plant.

“But under optimal conditions, large plants can produce 5,000 to 12,000 seeds per plant. Seeds are also spread by birds and seeds can float on water for up to 10 days,” she said.

Kindrachuk said the Guide to Crop Protection has a list of available control options and the correct crop staging.

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alice.mcfarlane@jpbg.ca

On Twitter: @AliceMcF