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Pest Patrol: Control of income-robbing weeds

#PestPatrol with Mike Cowbrough, OMAFRA

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.

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 management. More than two-thirds responded, and many reported having had similar experiences.

When asked which major weed control challenges occurred during the 2020 season, their reports included more than 20 different weed species. The most frequently mentioned species are illustrated using a word cloud, where the larger the text is for a weed species, the more often it was identified as being a problem to manage in field crops (Figure 1 at top). Lamb’s quarters and Canada fleabane continue their reign as top challenges.

Agronomists also shared their experiences on which management practices consistently result in good weed control. Not surprisingly, multiple and diverse methods for tackling weeds were consistently identified and are ranked in the second word cloud (Figure 2 at top).

Last, agronomists shared their general concerns on issues that not only affect their ability to successfully manage weeds but also have the potential to negatively affect relationships amongst neighbours when not proactively dealt with. Their most common concerns are illustrated in the final word cloud (Figure 3 below).

Figure 3. Issues identified as being of concern now and in the future. The issues are ranked in order from most frequently mentioned starting with: dicamba drift, poor lamb’s quarters control, late-emerging grasses, herbicide resistance, herbicide carryover, overreliance on Group 15 herbicides and tank-mix antagonism. photo: Supplied

Over the next several columns, I will tackle many of these issues with the objective of providing guidance on what can be done to address them.

Have a question you want answered? Hashtag #PestPatrol on Twitter to @cowbrough or email Mike at [email protected].

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