Aphids live on the underside of leaves of all sorts. While sitting on these leaves, they suck the sap of the leaf. Chances are that there will be a lot of them around. If there are, they can drink so much of the sap that the leaves of the plant curl. A heavy infestation can cause the fruits and even the flowers to wither and die.

Aphids can also cause other insects to appear in large numbers. They do this because they produce honeydew, which ants and some other insects eat. In order to get rid of many pests you need to get rid of aphids first.

Aphids and discarded aphid shells on a corn leaf.

Photo provided by Marlin Rice from the
Iowa State Univerity Gallery