Pea aphids are a sporadic pest in Manitoba, which overwinter in perennial legumes. Newly hatched adults fly to neighbouring pea crops and cause yield loss by feeding on peas during the pod formation and elongation stages, reducing seed formation and seed size.
Adult pea aphids are small, about 3 mm (1/8 in.) long and 1.5 mm (1/16 in.) wide, and range in colour from light to dark green. They are soft-bodied, pear shaped insects with long slim legs and antennae that have narrow dark bands at the tip of each segment. Pea aphid nymphs are smaller but look very similar to adults. Pea aphids can be winged or wingless.
- Begin scouting towards the end of June to early July, when 50-75% of the crop is in early flower.
- Check five plant tips (top 8 inches) or conduct 10 sweeps using a sweep net, at four locations (>50m apart) in each field.
- Assess populations along field edges and in the middle of the field. Populations may be higher near field edges.
Threshold and Control
The economic threshold was developed in Manitoba, using Century peas. The threshold is 2-3 aphids/plant tip or 90-120 aphids/10 sweeps, but varies with control cost and pea price.
If threshold is reached, apply registered foliar insecticide (Movento, Matador, Silencer, Voliam Xpress, Malathion, Lannate, Lagon or Cygon) at early pod (when 50% of plants have produced young pods). Natural enemies such as lady beetle, larvae of hoverfly, minute pirate bugs and damsel bugs and parasitic wasps, fungal diseases will also keep pea aphids populations in check.