Early flowering can be a really good check point for canola crops. Scouting at early flower can be very instructive for what to expect further along in the season, and it’s a great opportunity to see what insects are out there or could develop into an issue later in the season.
In this episode of the Canola School there’s plenty of information from Scott Meers, of Mayland Consulting. The three general questions you should be able to answer after sweeping at early flowering are:
- What insects are out there?
- Is the pest insect population at threshold?
- Do we need to do something about them or is there something we can do?
Generally, sweeping is done at early flowering for cabbage seed pod weevil, for example, where the threshold is two and half insects per sweep or 25 insects in 10 sweeps. Meers suggests looking at the Alberta Agriculture live reporting map (or other provincial reporting maps) for estimates of insect populations. Cabbage seedpod weevil is “not an everything situation,” says Meers, and that yield damage from this insect could cost 15 to 20 per cent.
But you never know what else is going to end up in your sweep net, including diamondback moth. Based on early season traps, it appears there was a flight recorded earlier this spring. Knowing your diamondback moth numbers at early flowering will indicate if you should be concerned at the end of flowering. “There’s a whole host of little wasps that take them out and each year it seems to be a different one. There are four or five main ones that have been identified on the Prairies,” says Meers.
Another one to keep an eye out at early flowering is lygus bug, even though at this stage it’s not an economic concern. The damage from this insect comes at podding stage, but it’s good to know what kind of a population you could expect. Lygus bugs go through two generations, one before canola comes into flower in roadside weeds, and one when canola is in flower or at early -flowering, when they lay eggs. Lygus numbers will really build as the crop is drying down.