Tackle seedling canola’s #1 threat: flea beetles
Varying flea beetle damage is being reported in all growing regions, with slow-growing canola at greatest risk. Part of the reason feeding varies – even between neighbouring fields – is that flea beetle feeding attracts more flea beetles. They are drawn both to the breakdown products of glucosinolates released from chewed plant tissue and the pheromones and chemical attractants released by other flea beetles.
Scout regularly and be ready to act if feeding approaches the 25% action threshold. Always follow label recommendations for rates and timing. Since pyrethroids lose efficacy above 25C and can work by ingestion as well as contact, best results will likely be achieved by applying during cooler parts of the day (early morning or evening). (The flea beetles spray decision: 8 steps)
Over-wet or finally not so dry, top dress now.
DRY AREAS: With precipitation occurring in many previously over-dry areas, yield potential may be higher than expected. Adjust yield targets – and nitrogen application plans – accordingly.
EXCESSIVELY WET AREAS: Residual soil nitrogen (in nitrate form) may now be largely depleted in over-wet soil, and spring-applied nitrogen will have largely converted to nitrate and be disappearing. Manitoba Agriculture’s soil fertility specialist John Heard suggests top dressing supplemental nitrogen based on N loss and yield assessments, but not to original application levels.
• Where N losses are estimated to be high and yield potential is still good, apply up to 2/3 of original targeted N rate.
• Where estimated N losses are moderate but yield potential is good, or where estimated losses are high but yield potential is fair, apply up to 1/3 of original targeted N rate.
Yellowing of lower leaves can be a symptom of nitrogen deficiency or excess moisture. See suggestions on assessing N losses here.
(Top dress tips for nitrogen and sulphur) (Crop response to foliar applied phosphorus)
What’s actually in those fields? COUNT and SCOUT
Especially where reseeding isn’t an option, watch the crop DAILY
Use CanolaCounts.ca with your free plant counting ring (email to request one) to assess your stand. Seeing poor or uneven emergence? It’s unlikely seed vigour is the problem; instead, consider these issues. Emerging canola can survive some waterlogging.
While assessing plant density, also watch for early season issues (especially weeds) and pests. Diamondback moth reports remain low; some fields are being sprayed for cutworms; flea beetles remain a concern in some regions. Wirestem is usually related to rhizoctonia. Zinc phosphide (Burrow Oat Bait, ZP Rodent Oat Bait AG) works as well as strychnine on Richardson’s ground squirrels.
(Reseed economics calculator)
When is the best time to spray weeds?
Early weed control always offers the best ROI but choosing application timing isn’t always simple. Since weather, product availability (and – in wet areas – risk of rutting) may limit second pass options, good control in pass #1 is critical. Watch the forecast. Glyphosate and Liberty are most effective on actively growing weeds; moisture-stressed weeds won’t respond as well to treatment. Liberty requires more time to be rainfast than some other products. (Spraying tips for tough conditions)
* Know what’s there. If you’re unsure about a weed’s ID, the SK Crop Protection Lab can help
* Keep it clean: clean that sprayer to avoid contamination catastrophes, especially when switching from glyphosate to Liberty.
* Apply it right. Using below-label rates of herbicides can contribute to development of resistance in some cases .