24 Agronomy Weeds, pests, and disease OMAFA EXTENSION SPECIALISTS WEIGH IN ON THE 2024 SEASON Matt McIntosh A MILD WINTER, WET SPRING, SURPRISE PESTS AND SOME USUAL SUSPECTS: 2024 was a typically atypical year in many respects. Here, Ontario Ministry of Agriculture, Food and Agribusiness (OMAFA) extension specialists share what stuck out to them – and what they’re thinking about ahead of spring 2025. MILD WINTER CHALLENGES A fairly mild winter in 2023/2024 ensured surface roots of some perennial weeds survived in greater numbers, making them tougher to control in the growing season, says Mike Cowbrough, the Ministry’s weed management specialist. Indeed, many weeds “came earlier and grew larger,” with control being even tougher in light of excessive moisture in some areas – west of London and Lambton County, for example. “Some wild carrot reached a stage of tolerance that it didn’t matter what you threw at it,” says Cowbrough. At the time of writing [mid-October], he expressed hope that a continuation of mild autumn conditions would provide an opportunity to attack weeds when susceptible going into winter. The proliferation of waterhemp is also continuing, albeit not necessarily quickly. Still, Cowbrough emphasizes that growers should be aware that it remains on the march. More unusual was a generally observed increase in pressure from grasses in the Lolium genus – ryegrass and bluegrass, for example. “It’s a complicated genus with lots of hybridization,” Cowbrough says. Through a weed identification program operated in conjunction with his horticulture counterpart, Kristen Obeid, a high percentage of submitted Lolium grass samples were found to be glyphosate-resistant. Cowbrough is unsure why this is happening, although possible sources of pressure could be turf blends – Lolium grasses are very common in turf blends – or seed spread from roadsides. But whether the grass problem of 2024 is a sign of things to come or a weird anomaly remains to be seen. Problems aside, 2024 also reinforced some positive trends in weed control. “I’m encouraged by the adoption of residual herbicide programs. Two-pass strategies in corn and soybeans, which maybe wasn’t there five or ten years ago. It’s minimizing risk,” Cowbrough says. “I think there are some progressive people who dabble in entry-level cover crops like cereal rye or oats. I think that’s been helpful. I do see a little bit more diversity in terms of weed management.” Getting on top of soil management is also critical, given the mild 2023-2024 winter. According to Colin Elgie, OMAFA field crop soil fertility specialist, the lack of winter frost and generally wet conditions holding until August made soil conditions “tight and challenging” for root development and nutrient uptake. A clear difference was observed between fields where more active soil management programs were implemented and those where planting occurred in less-than-ideal conditions – the latter showing earlier and more nutrient deficiency symptoms. Elgie’s take-home message, consequently, is “the need to soil sample.” “Lately, I’ve been getting questions on where [and] how to cut back on fertilizer with crop prices dropping off and fertilizer prices staying relatively steady,” he says. “The TAR SPOT STRIPE RUST
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