Aphids (Small grains)
English grain aphid – Sitobion avenae Fabricius,
Bird-cherry oat aphid – Rhopalosiphum padi Linnaeus
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Appearance and Life History
Photo by J. Obermeyer
A number of aphid species may be found on small grains in the Midwest. English grain aphid and bird-cherry oat aphid, both described below, are the most common aphid pests of small grains in Indiana.
English grain aphid occurs both as wingless and winged forms. The wingless form is pale green with long black antennae and cornicles (the two projections from their posterior end). The winged English grain aphid is identical to the wingless form, except that it has wings and dark lobes on its thorax (the area immediately behind its head).
Bird-cherry oat aphid also has wingless and winged forms. The wingless form is olive-green and often has a large reddish-brown spot or spots on the posterior part of its body. The winged formed is predominantly black in color.
Damage
Both of these aphid species injure small grains by sucking plant juices from the leaves, stems, and/or heads. As the heads begin to form, clusters of aphids may feed on the developing kernels resulting in shriveling and shrinking of the grain. They can also cause severe losses by serving as vectors of barley yellow dwarf virus (BYDV), a disease that causes yield reductions in small grains in the Midwest.
Photo by J. Obermeyer
Photo by J. Obermeyer
Photo by J. Obermeyer
Sampling Method
- Necessary only if a significant number of English grain aphid, bird-cherry oat aphid, or any other aphid species are observed during regular field visits.
- Examine 20 stems in each of 5 areas of the field.
- Count and record the number of aphids found; determine the average number of aphids per stem.
- Record the number of parasitized aphids (mummified; gray to brown and balloon-shaped) and any beneficial insects, such as lady beetle adults and larvae and lacewing larvae.
- Note the stage of development of the plants.
Management Guidelines
Corn Insect Control Recommendations: E-series 220-W (PDF)
- Control may be advisable if an average of 20 or more aphids per stem are noted while plants are in the tillering stages (growth stages 1-5); an average of 30 or more aphids per stem when plants are in the pre-boot stages (growth stages 6-9); or an average of 50 or more aphids per stem when plants are in the boot, heading, and/or ripening stages (growth stages 9-11).