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Section 26.6.5: Corn Leaf Aphid

Rhopalosiphum maidis

Time of concern: May through September. Early tassel through harvest
Key characteristics: Corn leaf aphids are greenish blue with black legs. Colonies buildup in the curls of leaves and on stems on the upper part of the plant. Infestations produce large amounts of honeydew on which black, sooty mold develops. High populations can cause discoloration of outside husk layers. Corn leaf aphids are an important vector of maize dwarf mosaic virus. 

Management Option Guideline
Scouting/thresholds

Processing sweet corn - Insecticide treatments are rarely justified, and populations are normally controlled by sprays directed at caterpillars.
Fresh-market sweet corn - Use the sampling program for European corn borer.  If 50 percent of the plants have 50 or more aphids per emerging tassel, treatment may be necessary to maintain acceptable quality. 

Fresh Market Sweet Corn IPM Scouting Procedures

Natural enemies

A variety of predators, especially lady beetles, parasitoids, and pathogens help suppress infestations. Scouting and following thresholds for the worm pests to minimize insecticide use can help preserve natural enemies as can choosing an insecticide with a low impact on natural enemies. Bt varieties have been shown to be effective against the worm pests while conserving natural enemies. Use Natural Enemies of Vegetable Insect Pests for identification of natural enemies.

Resistant varieties No resistant varieties are available.
Site selection/planting Early-season corn is less likely to be infested.
Insecticide Resistance Management

The Insecticide Resistance Action Committee (IRAC) has classified insecticides into resistance management groups. Most insecticides include an IRAC group number on the front page of the label. Alternating between insecticides with different group numbers will help avoid the development of resistant insect populations.

Crop rotation, Postharvest, and Sanitation These are not currently viable management options.
Pesticides Cornell Integrated Crop and Pest Management Guidelines for Commercial Vegetable Production