Insect update

Lygus populations continue to be high and exceed thresholds in parts of Alberta and Manitoba (around Morris and Altona). Once pods become leathery (rule of thumb is about two weeks before swathing), then even adult lygus cannot cause damage and control is not economical. Economic control thresholds for lygus bugs are based on adult and late instar counts. When canola prices are $12 per bushel and application costs are $12 per acre, the threshold is 11 adults or late instar bugs per 10 sweeps. Click here for more infomation on lygus bug. Spraying for Bertha armyworm is wrapping up in most areas but is still occurring in southeastern Saskatchewan. Populations below threshold are being monitored in north central Alberta (around Hairy Hill and St. Paul). The threshold for bertha is 17 per square meter when canola is $12 and application costs are $12 per acre. Click here for more information on bertha armyworm. Reports of heavy populations of Imported Cabbageworm larva continue in western Saskatchewan. Remember that this insect tends to feed on leaves and it is not usually economical to spray them. Click here for information on how to identify late-season insect larva such as bertha armyworm, diamondback moth, and imported cabbageworm. 

Keep scouting latest crops for late-season insect pressure. Pay attention to pre-harvest intervals (defined as the time between spraying and cutting) this late in the growing season. Once a crop is within 7 days of being swathed, no insecticides can be applied. It is vital that all of Canada’s canola is Export Ready. Click here for a quick reference of pre-harvest intervals for insecticides and fungicides in canola.