Impact
High populations of aphids other than RWA can occur but seldom require treatment. Impact varies with an aphid species and plant growth stage. Natural predators generally control aphid populations.

Description and Symptoms

Aphids feed on the plant carbohydrates and can damage the flag leaf and grain head.

Research in North and South Dakota and in Minnesota suggests aphid damage may be critical at late growth stages.

Aphid feeding commonly creates a sticky substance or "honeydew."

Typical aphids of the San Luis Valley include:

Corn leaf aphid (Rhopalosiphum maidis) has a pale green abdomen with dusky lateral areas. Cornicle and appendages also are dusky. English grain aphid (Macrosiphum avenae) is grass-green, sometimes yellowish or pinkish brown on the head, frequently with a dusky blotch on the abdomen. The cornicle is entirely dusky to black.

Greenbug (Schizaphis graminum) is yellowish-green with a dark green longitudinal stripe. The cornicles are pale with a dusky tip.

Oatbird cherry aphid (Rhopalosiphum padi) is dark with an orange posterior. Cornicles are brownish with black tips.

Integrated Management

Scout fields regularly when aphid populations appear.

Use the following chart for economic thresholds to decide when to treat aphids other than the RWA with a pesticide.

This material is based on work supported by the San Luis Valley Water Quality Demonstration Project Best Management Practices Advisory Committee, Colorado State University Cooperative Extension, Farm Service Agency, Natural Resources Conservation Service, and the U.S. Department of Agriculture under authorization as 1991 U.S. Department of Agriculture Water Quality Demonstration Project.