Scouting Tips
- Begin scouting toward the end of June to early July, when 50 to 75 per cent of the crop is in early flower.
- Check five plant tips (top eight inches) or conduct 10 sweeps using a sweep net, at four locations (greater than 50 metres apart) in each field. If you’re inspecting plant tips, unfold the clam leaf (newest stipule) to check inside for aphids.
- Assess populations in various locations of the field, including field edges. Pea aphid populations may be higher near field edges.
Watch the Scouting Video!!
Note: The agronomist in the video should have also opened the clam leaf to check for pea aphids.
Threshold and Control
The economic threshold for control is two to three aphids/plant tip or 90 to 120 aphids per 10 sweeps (or nine to 12 aphids per single sweep). If the threshold is reached, apply a registered foliar insecticide at early pod (when 50 per cent of plants have produced young pods).
This economic threshold was based on $5.71 per bushel for peas and an older pea variety, Century. While higher crop prices exist today compared to when this threshold was developed, current pea varieties are also expected to be able to tolerate more aphid feeding than Century peas. As a result, the threshold of two to three aphids/plant tip or nine to 12 aphids per sweep is maintained.
Natural enemies including lady beetles and larvae, hoverfly larvae, minute pirate bugs, damsel bugs, parasitic wasps and fungal diseases will also keep pea aphids populations in check. Look for these natural enemies while scouting for pea aphids and consider them in your management decisions.
Research in Manitoba has shown that insecticides applied when pods first form protects pea yield better than earlier or later applications. Control at the early pod stage (when 50 per cent of plants have produced young pods) provides protection through the pod formation and elongation stages, which are very sensitive to aphid damage. Aphid feeding on peas during the flowering and early pod stages can result in lower yields due to less seed formation and smaller seed size. Protein content and other quality issues do not appear to be affected.
Table 1. Yield loss in peas for average aphid counts per sweep or per 20 centimetre plant tip when approximately 25 per cent of the field has began flowering.
| Aphids per sweep | Aphids per tip | Per cent Yield Loss |
| 7 | 1 | 3.4 |
| 10 | 2 | 4.9 |
| 12 | 3 | 6.1 |
| 15 | 4 | 7.1 |
| 16 | 5 | 8.0 |
| 18 | 6 | 8.8 |
| 20 | 7 | 9.6 |
| 21 | 8 | 10.3 |
Pea aphid thresholds in faba beans are higher than in peas. The action threshold of 34 to 50 aphids per main branch gives a seven day lead time before injury levels are reached (96 to 142 per main branch).
Additional Resources
Pea aphids on peas, faba beans and lentils – Manitoba Agriculture and Resource Development
Controlling Pea Aphids in Lentils and Faba Beans – Pulse Beat Issue 90 article by Ningxing Zhou, Sean Prager (University of Saskatchewan) and Tyler Wist (Agriculture and Agri-Food Canada)