Answer: Sounds like corn leaf aphids ( Rhopalosiphum maidis ). These dark, blue-green aphids attack corn plants in the early-tassel stage, feeding on the leaves and tassels. Affected leaves become mottled with yellow spots, and the tassels may gum with pollen and encourage sooty mold fungus to form. Severely injured tassels may fail to produce pollen. Corn leaf aphids are more of a problem during warm weather (80 F) and seem to favor later-maturing, hybrid sweet corn varieties, such as 'Breeder's Choice'.Control aphids with insecticidal soap. Spray as soon as you notice activity. Clean up the garden plot in fall to remove overwintering sites. If the problem is chronic, you might do better growing earlier-maturing sweet corn varieties, such as 'Early Choice'.
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