10. Scout regularly. Go out at least once a week. If you see elevated numbers, visit the field more frequently.
9. Choose an appropriate time of day. Lygus, for example, are most active on warm, calm days between 10 a.m. and 4 p.m. However, morning or evening tend to be the more active times for bertha larvae.
8. Note the weather conditions while scouting. Insects, especially those scouted with a sweep net, may be lower down in the canopy during hot afternoons or heavy winds.
7. Stage of canola. The insects may be present, but control may not be necessary. For example, cabbage seedpod weevil do not need to be controlled after 30% flower and lygus bugs do not need to be controlled after pods are leathery.
6. Look for beneficial insects as well as pests. Get to know some of the key beneficial insects.
5. Use the right scouting technique for the insect. Lygus and cabbage seedpod weevil thresholds are based on sweep net counts. Diamondback thresholds are based on larvae shaken loose after hitting plants on the hood of the truck. Bertha thresholds are based on how many larvae found on the ground after shaking plants in a quarter square metre.
4. Check 5 to 15 locations at least 50 metres apart. Do not sample headlands or areas within the crop that are not representative of the field. Use the average number of larvae at the sites surveyed to determine if the economic threshold has been exceeded.
3. Record what you find. With detailed records, including insects found in each field, insect numbers, what they’re feeding on, time of day, temperature and weather conditions, you know which fields to scout more frequently, and you have comparison points for other fields and other years.
2. Follow thresholds. Every major insect of pest of canola has an economic control threshold. See the table below.
1. Pre-harvest intervals. If spraying is necessary, choose a product with a pre-harvest interval that fits within the timeframe between spraying and cutting the crop.
Here’s a PDF if you want to print off a clear version: Thresholds chart