How to Control Corn Leaf Aphids

Corn leaf aphids can damage crops quickly.

Corn aphids, which have the official name of Rhopalosiphum maidis, are different from other aphid varieties. Corn aphids have blue or light green bodies and may or may not have wings. Infestations are most identified by black spots on the exterior of the corn. These are mold growing on insect secretions. Controlling corn aphid infestations requires insecticidal sprays that are most effective when the cornstalks are below 5 feet tall.

Things You'll Need

• Garden sprayer or industrial crop sprayer
• Insecticide
• Water

Instructions

1. Examine the cornstalks carefully to determine the number of aphids on each one. If there are more than 100 aphids on 50 percent of stalks without tassels or on 3 percent of those with tassels, treatment is required. Lower populations of aphids typically do not cause severe corn damage.

2. Open a garden sprayer and add an insecticide with one of the following primary ingredients: dimethoate or esfenvalerate. If you are growing sweet corn, use an insecticide with endosulfan. Use only the amounts specified on the bottles for the amount of land you are treating.

3. Add the recommended amount of water into the garden sprayer, as specified on the insecticide bottle. Close up the sprayer and shake it well to combine the ingredients.

4. Spray the mixture onto all areas of the cornstalks including the actual stalks, leaves and the hairlike projections called tassels at the top of the stalks where aphids often hide. Complete saturation is critical for adequate control.

Tips & Warnings

• To control the corn aphids organically, spray the cornstalks and foliage with an insecticidal oil, which smothers the aphids and kills them. As with insecticide, complete saturation is required.

References

• "University of California"; Corn Aphids; L. D. Godfrey, et al.; January 2006
• "University of Illinois Extension"; Corn Leaf Aphid; Susan T. Ratcliffe, et al.