Lygus bugs management in canola begins with sweep netting at late flowering and pod stages. Count adults and late instars. The standard threshold is 20-30 per 10 sweeps.
The most vulnerable crop stage for lygus feeding is after flowering and when seeds are enlarging on lower pods.
Scouting
Scout lygus at late flowering and podding stages using a standard insect sweep net of 38 cm (15″) diameter. Take ten 180° sweeps, and aim to sweep the flowers and pods while moving forward. In thick crops, take a couple of steps and stand while sweeping vigorously. If you are not seeing a few pods in the net, sweep harder. Count the number of big lygus in the net. Sweep net technique.
Count adults and late-instar nymphs
Nymphs are young lygus, and only the larger nymphs do enough damage to be included in sweep net counts. (See the images below.) A key feature is the black dots on the back. Count nymphs with developing wingpads or dark shoulder blades. Don’t count those nymphs without developing wings.
Small nymphs (without black dots) don’t feed very aggressively, and they are vulnerable to heavy rains and wind that push them down in the canopy or to the ground where they drown or other insects eat them. If you are seeing a lot of earlier nymphs, check again every few days. It may take as little as a week for lygus to grow from early to late instar stages. If swathing is a week away and most lygus are small nymphs, these are unlikely to be a threat before the crop is cut.
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