Watch for blackleg. Blackleg stem girdling has appeared in fields in Manitoba and western Saskatchewan — and it seems to be worse in tight canola rotations. Blackleg is a key reason why one-year-in-four rotations are recommended for canola. With tighter rotations, growers are selecting for blackleg to break down the resistance in R-rated varieties. The answer for next year is to rotate that field away from canola. And next time canola goes on that field, try a variety with a different source of resistance. Switching to a different herbicide tolerance system provides an opportunity to control volunteers that can become infected early — adding to disease pressure.
We’ve heard talk of spraying fungicide on hailed fields to keep blackleg from entering the plant through broken tissue. If growers are contemplating a fungicide application, they should also consider yield potential of the remaining crop and the risk of fall frost due to the delayed maturity, which could negate the benefits of the application. Products registered for blackleg suppression are normally applied prior to bolting, so check the product’s pre-harvest interval if crops are at later growth stages.
Impact of hail. Hail at flowering may not cause much yield loss but will delay maturity, increasing fall frost risk. When buds and flowers are lost due to injury, the plant recovers rapidly by developing additional flowers that normally would have been aborted. The plant also develops flowering branches from growth buds lower down on the plant, replacing to a degree, the lost buds, flowers and pods. Hail at podding means permanent loss. If hail strikes during pod filling or ripening, plant recovery is not possible.
Sclerotinia. It has been a busy year for sclerotinia spraying. In fields at 20% to 30% flower with good yield potential and moist conditions, a spray to prevent sclerotinia stem rot may still be worthwhile. If fields are too wet for a ground sprayer, aerial application is an option.
Weedy fields. Producers planning a pre-harvest application to control larger weeds and make harvest easier need to avoid off label applications. Higher rates could increase the risk of residues from the pesticides, which can become an export issue with canola customers.
Scouting fields. When scouting at flowering, look for evidence of diamondback moth (read the article below) and if you see wilting plants, pull them and look for root maggots, root rot, blackleg and clubroot. For more tips on scouting at flowering, click here to hear Murray Hartman, Alberta provincial oilseeds specialist, on ACPC radio.