Each year, aphids emerge in cereal crops in a fairly regular pattern in Western Canada.
Mid-July rolls around and, depending upon what's been happening in the growing regions south of our Canadian border, winged cereal aphids could be catching a ride on the winds flowing northward. Flying to the greener pastures of the Western Canadian prairies to catch the later planted cereals.
Two Aphids, One Field
Two species of aphid commonly infest cereals (wheat, barley, oats, rye, durum, and canary seed) in Canada; the English grain aphid, Sitobion avenae, and the Birdcherry-oat aphid, Rhopalosiphum padi. They can occur singly or together in your fields.
Both aphid species give birth to live young (Figure 1) and are all female so populations can build up quickly once aphids establish in a field.
The English grain aphid is larger and typically a lighter green colour than the Birdcherry-oat aphid. It has slightly longer and fully black cornicles on the upper end of it's abdomen (Fig. 1).
The birdcherry-oat aphid has a red "saddle-like" pattern on the top of it's abdomen. It is often a darker, olive-green colour (Figure 1).
The English grain aphid can have a red morph that is induced by high light intensity (Tourgeron et al. 2021. Body-color plasticity of the English grain aphid in response to light in both laboratory and field conditions. Ev Ecol 35) (Figure 2).
Both species feed in cereal heads, where the seed gets its nutrients while filling, so they are often found in colonies at the base of a floret (Figure 2). The Birdcherry-oat aphid also infests the boot of cereals and is more likely to be on leaves than the English grain aphid.
Managing Your Fields
If cereal aphids arrive earlier in the season, while seeds are still filling, use an economic threshold of 12-15 aphids per tiller. Remember that this is an average of 12-15 aphids per tiller. You still need to scout in multiple areas of each field.
If your crop has passed the soft-dough stage, it is no longer in danger from cereal aphids. Agriculture and Agri-Food Canada scientists created a smartphone app that helps with scouting, identification, timing and understanding economic thresholds of cereal aphids in your field. It uses the presence of natural enemies (along with pictures for identification and counting) to dynamically move the economic threshold.
This Cereal Aphid Manager app is available in the Google Play and the Apple stores and the link to download it can be accessed through this QR code (Figure 3). The app suggests that you scout from 25 to 100 tillers in a field before making any control decisions and will calculate an average number of aphids per tiller as you scout.