A quick method to check for pea aphids is to rip off the top 8 inches of a pea plant and then unfold the clam leaf (newest stipule) to check inside for aphids. Tap the plant tip into the palm of your hand a few times, and count how many little green aphids you find. Do this with five pea plants at four different sites per field, making sure each site is more than 50m apart from each other. Pea aphids can be found in higher numbers along field edges. From those 20 plants, if you average 2-3 aphids or more per plant tip, then an insecticide application when 50% of the pea plants have produced some young pods will be cost effective.
Seeing lady bugs in the field can be a good indication that pea aphid are present since lady bugs eat pea aphids.
Pea aphid thresholds in faba beans are higher than in field peas.
More information and a chart that outlines % yield loss and corresponding pea aphids numbers, click below.