Dry year adds to spray considerations

Manitoba’s weather lately means weeds have toughened up and herbicides may have an uphill battle if weeds aren’t growing vigorously

Kochia's fuzzy leaves makes treating it with a herbicide more of a challenge.

This year has brought its own quirks to weed control.

Kochia is out in force again this year, provincial weed specialist Tammy Jones said. The plants’ fuzzy leaves create their own challenges for herbicide contact, even if the kochia is not showing glyphosate resistance.

Glyphosate-resistant kochia has become a significant headache and cause for worry on the Prairies, and 2019 has done little to dampen the concern.

Jones urged producers to test if they suspect glyphosate resistance, since environmental conditions like frost might also be impacting how well herbicide works.

Canola growers can get that test for free. The Manitoba Canola Growers is offering one free clubroot, blackleg race and glyphosate-resistant kochia test for each of its members. Taken together, the tests through the Pest Surveillance Initiative Lab would ordinarily cost $450, the canola group says, while the kochia test alone is valued at $125.

The dry conditions have also led to a rise in Russian thistle, according to Jones.

The small seedlings are commonly mistaken for a grassy weed, she said, but grow into a tumbleweed-like plant that thrives in light, sandy soils.

Lamb’s quarters, meanwhile, has created it’s own problems.

Waxy leaves make it difficult to get herbicide contact, Jones said, while the dry conditions have caused plants to fold leaves up. The result is even harder to control than usual, the weed specialist said, since herbicide will roll off leaves before any uptake can happen.

Jones urged producers to triple scout the field; once before spray to confirm staging, once soon after spraying, and once 14 days later to determine if another pass is needed.

It may be a year for more than one pass, especially on slow-to-germinate fields, she also noted. Staging has been an issue in a one-pass system this year, with winter annuals and perennials pulling ahead while annuals lagged with the crop, she also said back in May. She doubled down on that message during a recent Crop Talk webinar. Rain at this stage may also bring additional weed flushes, she warned.

Jones urged farmers not to back off on rates or water volume and to keep a close eye on droplet size to maximize coverage, given the challenging season. Farmers may also want to double-check rates for their particular weeds.

Herbicide drift is once again a perennial issue. Sprayers101.com suggests farmers cut spray off when wind reaches 20 to 25 kilometres an hour; although Jones suggests caution once wind speeds reach 15 kilometres an hour.

Producers up against a time restraint may be able to push that with precaution, she said. She reminded producers to keep their boom low and consider things like volatility, nozzle type, what they’re spraying, droplet size and what crops are downwind.

Sprayers101.com recommends that booms still be high enough for low-drift nozzles to overlap 100 per cent for uniform application.

About the author


Alexis Stockford

Alexis Stockford is a journalist and photographer with the Manitoba Co-operator. She previously reported with the Morden Times and was news editor of  campus newspaper, The Omega, at Thompson Rivers University in Kamloops, BC. She grew up on a mixed farm near Miami, Man.



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