GFM Network News


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

Figure 3. Interveinal yellowing and browning typical of SDS infection.

Pest Patrol: Soybean cyst nematode (SCN) and sudden death syndrome (SDS)

#PestPatrol with Albert Tenuta, OMAFRA

Reading Time: 2 minutes The dry conditions in 2020 have been favourable for soybean cyst nematode (SCN) infection. A reminder that you can look for SCN by digging up plants with a shovel and gently removing soil and examining roots for the presence of the small white to yellow cysts (Figure 1 below). Cysts are considerably smaller (1 mm) […] 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


Figure 1. Attempted mixing of Dual II Magnum with ATS as the carrier (left) compared to successful mixing with water (right).

Pest Patrol: The importance of doing a ‘jar test’ with fertilizers and herbicides

#PestPatrol with Mike Cowbrough, OMAFRA

Reading Time: 4 minutes Each year I get more questions about mixing the liquid fertilizer, ammonium thiosulphate (ATS), with herbicides. With reductions in atmospheric sulphur deposits, Ontario research has shown positive yield responses in some crops when sulphur fertilizers are applied, so it makes sense that farmers are looking at ways to add sulphur to their crop in an […] Read more

Weed control with Authority Supreme (Groups 14 and 15), notice that overall weed control is good with the exception of Canada fleabane.

Pest Patrol: Weed control in IP soybeans

#PestPatrol with Mike Cowbrough, OMAFRA

Reading Time: 2 minutes For more than a decade now, the University of Guelph and OMAFRA have been comparing the level of weed control, crop safety and grain yield associated with different herbicide programs in food grade, non-GMO soybeans, otherwise known as IP (identity preserved) soybeans. Table 1 (see below) summarizes the weed control and crop injury achieved with […] Read more