Four questions to test your knowledge on pre-harvest intervals.
The swath timing decision becomes more difficult in crops with plants at multiple stages of growth. Here are some tips to help with the swath decision on these fields….
Diamondback moth larvae and grasshoppers have been reported, but so far nothing of widespread significance. The photo shows what grasshoppers can do to a canola plant, but their damage is usually isolated to small patches. Bertha armyworm adult traps are coming down with very little in the way of hotspots.
Improved moisture in some regions has extended flowering. Some fields have been at “full flower” for what seems like weeks. Highly variable crops may also be at full flower or their “most yellow” — other terms for 50% flower — for longer than typically expected. This does extend the sclerotinia stem rot risk. But that “risk” may still not be high enough to warrant a fungicide spray — given the risk was so low before and that late applications tend to have a reduced benefit for yield.
When it comes to maintaining Canada’s reputation as a high quality canola supplier, everyone in the canola value chain has an important role to play.
Late season hail can damage pods and increase the shattering risk for those pods. Before jumping the gun and swathing too early, take these decision-making steps….
Threshold tables for lygus suggest, for example, that if canola is $12 per bushel and spray costs $8 per acre, the threshold at the early pod stage is 5 lygus adults or late instar nymphs per 10 sweeps.
Current thinking is that 5 lygus per 10 sweeps (0.5 per sweep) is too few to warrant a spray, and that the economic threshold is likely quite a bit higher. This is certainly the case for canola growing strong with decent moisture.
Swede midge females lay their eggs in canola apical meristems (growing points). Larvae hatching from those eggs feed within the meristems. Plant damage depends on the canola growth stage at which feeding occurs. The younger the canola plant, the greater the damage.
Damage typically includes one or more of the following….
Swede midge caused some yield loss in northeast Saskatchewan in 2013, and caused heavy yield losses in the major Ontario canola growing region. Swede midge’s flexible biology could make it well adapted to the Prairies, like wheat midge is today.
Insecticides are registered for swede midge, but there are no viable recommendations for control at this point. There are no established economic thresholds or proven best timing for foliar sprays. The good news is that while their range seems to be expanding on the Prairies, swede midge numbers remain fairly low so far.
Glyphosate is registered for pre-harvest perennial weed control in canola. Glyphosate is to be applied when the majority of seeds are yellow to brown in colour and seed moisture is less than 30%. Heat fits between glyphosate and Reglone on the speed of dry down spectrum. Reglone is a contact herbicide (only kills what it contacts) and is registered in canola to dry immature green material to facilitate harvest. Reglone does not hasten crop maturity. It shuts the plant down quickly and basically STOPS it from maturing, which can lock in high green seed levels if applied prematurely.
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