GFM Network News


Pigweed at the two-leaf stage of growth which is the optimum stage for some post-emergent herbicides.

PHOTOS: Pest Patrol: Maximum weed stage where herbicides are still effective

#PestPatrol with Mike Cowbrough, OMAFRA

Reading Time: < 1 minute A generation of glyphosate use has redefined what we mean by “apply herbicides to weeds that are small and actively growing.” Many interpret “small” to mean “about 15 cm” (six inches). If using “older” herbicides to manage glyphosate resistant weeds and your idea of small is 15 cm, then you may be disappointed with the […] Read more

The stage of lamb’s quarters when it is most susceptible to conventional herbicides. When lamb’s quarters is taller than 10 cm, control with glyphosate is reduced when applying at a rate of 0.67 l/ac. (540 g/l concentration). Increasing the rate to 1.34 l/ac. is needed to achieve adequate control.

Pest Patrol: Maximizing control of common lamb’s quarters

#PestPatrol with Mike Cowbrough, OMAFRA

Reading Time: 2 minutes Lamb’s quarters has consistently been identified as the most abundant and problematic weed affecting field crop production in Ontario even though the Pest Management Regulatory Agency database contains hundreds of herbicides that list lamb’s quarters as a susceptible weed. There is an arsenal of products available to farmers for the control of this weed, so […] Read more


Pest Patrol: Controlling weeds in non-GMO soybeans

Pest Patrol: Controlling weeds in non-GMO soybeans

#PestPatrol with Mike Cowbrough, OMAFRA

Reading Time: 3 minutes Weed control has always been a concern in non-GMO soybeans. Control of broadleaf weeds like lamb’s quarters and common ragweed has been inconsistent, and growers are always looking for ways to improve their results. General principles for weed control in non-GMO soybeans 1. Budget $80 to $85 per acre for weed control and plan for […] Read more

Canada fleabane rosette during October.

Pest Patrol: Management practices that controlled glyphosate-resistant weeds in 2020

#PestPatrol with Mike Cowbrough, OMAFRA

Reading Time: 3 minutes Several Ontario agronomists recently shared their most successful strategies for managing glyphosate-resistant weeds. Four general strategies were identified: 1. Inclusion of winter wheat in the crop rotation By early spring, winter wheat’s dense ground cover does not provide a good environment for annual weeds, like waterhemp, to germinate. There are also many herbicides that are […] Read more


Figure 1: Annual bluegrass.

Pest Patrol: Bluegrass becomes an emerging problem in field crops

#PestPatrol with Mike Cowbrough, OMAFRA

Reading Time: 4 minutes In Ontario, turf-like grassy weeds are being found in more cultivated fields. In herbicide-tolerant corn and soybean, control with glyphosate has been inconsistent. In cereal and forage crops, fast growth of these grasses in the spring makes them too big to be controlled with herbicides. Let’s review what is being found in fields and how […] Read more

Soybean planting showing leaf injury symptoms caused by a “bleaching” herbicide.

Pest Patrol: Crop injury from herbicide residues more common in 2020

#PestPatrol with Mike Cowbrough, OMAFRA

Reading Time: 4 minutes In 2020, a few farmers observed leaf injury in their soybean crops. The injury caused parts of the leaf to turn white, then yellow (see photo at top). This injury is typically caused by “bleaching” herbicides. It was odd, though, because the bleaching herbicide had been applied to the previous year’s corn crop, and it […] Read more


Figure 1 (left). These are the most often mentioned “challenging to control” weed species. In order from most common to least common: lamb’s quarters, Canada fleabane, foxtails, pigweed, common ragweed, giant ragweed, wild carrot, waterhemp, sow-thistle, velvetleaf, fall panicum, wild oats, vetch and bluegrass. Figure 2 (right). Management practices identified by agronomists that improved on-farm weed control. Management practices are ranked beginning with most often mentioned: fall weed control, residual herbicides, multiple modes of action, crop rotation, soil fertility, cover crops, scouting and two-pass herbicide applications.

Pest Patrol: Control of income-robbing weeds

#PestPatrol with Mike Cowbrough, OMAFRA

Reading Time: 2 minutes All farmers know that poor weed control reduces income. Staying on top of income-robbing weeds requires two things: first, knowing which species cause farmers the most grief and, second, understanding which management practices consistently provide good weed control. I asked over 30 agronomists from across Ontario to share their biggest challenges and successes in weed […] Read more

Figure 1. Dog strangling vine along a roadside in York Region where it is creeping into the fenceline and bordering corn field.

Pest Patrol: Dog strangling vine control with herbicides

#PestPatrol with Mike Cowbrough, OMAFRA

Reading Time: 2 minutes An invasive perennial weed from the milkweed family, dog strangling vine is extremely difficult to control once it gets established (Figure 1 at top). Progress has been made on biological control of this weed in Ontario through the release of Hypena opulenta, a leaf-feeding caterpillar. However, integrated strategies that include both biological and chemical methods […] Read more


Waterhemp towers above a soybean canopy.

Pest Patrol: How accurate are plant identification apps when it comes to weeds?

#PestPatrol with Mike Cowbrough, OMAFRA

Reading Time: 2 minutes Recommendations for plant identification apps were recently making the rounds on social media. Of course it would be nice to accurately identify an unknown weed in your field by taking a picture instead of sending it to an “expert” or a diagnostic lab. However, many of the top-rated plant identification apps are not particularly accurate […] Read more

Figure 1: The untreated control plot.

Pest Patrol: The latest word on nipplewort in cereals

#PestPatrol with Mike Cowbrough, OMAFRA

Reading Time: 3 minutes Here’s a question in my in-box. “I have a customer with a no-till rotation that has nipplewort — a lot of it. We found some pretty decent options for most crops in the rotation to clean it up before planting, but he’s got some in his wheat this year too. “What would be our best […] Read more