Corn Leaf Aphid
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Corn leaf aphid (Rhopalosiphum maidis) is very common in whorl-stage corn in Kentucky. It rarely causes yield loss but can be a contaminant in sweet corn. Infestations are more common in late-planted corn. Corn is most susceptible to yield loss by aphids while in the whorl stage. If large numbers are present three weeks before tassel emergence, physiological damage and some yield loss may occur. Excessive honeydew on the tassels may limit pollen shed, and it has been associated with barren corn, although this connection is uncommon. Corn leaf aphids vary from blue-green to gray and are small (1/8 inch or less) with a dark pair of tubes (cornicles) that project toward the rear.
Corn leaf aphids infesting flag leaf of sweet corn.
(Photo: UK Vegetable IPM Team, University of Kentucky)
Management:
- Monitor for corn leaf aphid twice prior to tasseling.
- Consider treating for corn leaf aphids if an average of 15 or more aphids (10 with stressed plants) per whorl are found three weeks before tassel emergence or 30 or more aphids (15 with stressed plants) per whorl are found one week later.
