Lygus hotspots: Lygus numbers are high in some regions, with reports of 70+ per 10 sweeps in some fields in central and northern Alberta. Some fields will warrant a spray, but seeing the plane next door does not mean all canola in the area should get sprayed. Assess each field. More on lygus thresholds.
Bertha armyworm hotspots: Berthas are a very low numbers in most areas, but there are a few hotspots. Bertha numbers can be high in one field, or even in areas within a field, and not a threat at all in fields close by. Assess each field. More on bertha armyworm thresholds.
Also note that beneficial insects, viruses and fungi can take down a high bertha armyworm population within a year. For this reason, high numbers in a field last year doesn’t mean you’ll find high numbers this year.
Exit holes from cabbage seedpod weevil. If 25% of pods or less have exit holes, your spray worked, or if you didn’t spray, you made the right decision. A check strip would be especially helpful in determining whether a spray paid off.
Consider the pre-harvest interval when making an insecticide choice.