Corn Blotch Leaf Miner

Agromyza parvicornis

The egg is small, milky white, longer than it is wide, and has a slight constriction in the center. The larva is green to white and about 1/4 inch long when full grown. The larva pupates in the mine between the leaf tissues in a reddish-brown puparium. The adult is a gray to brown fly slightly more than 1/4 inch long.

Corn Blotch Leaf Miner
Figure 1. Corn Blotch Leaf Miner

Life Cycle
This insect apparently winters as a mature larva or pupa in a puparium. In the spring the adults emerge and within 5 to 10 days begin to insert eggs in either the upper or lower leaf surface of corn or one of the broadleaf millets. Females may lay 100 or more eggs during their life span. The larvae hatching from them tunnel in the leaf tissues, leaving mines or transparent galleries. Often many mines appear on a single leaf. The larvae pupate in the leaf tunnel and emerge as flies in two or three weeks. From four to six weeks are required to complete the entire life cycle. Thus there are probably three to five generations each year.

The damage done by this pest is believed to be of little or no economic importance. The leaf mining seldom consumes a very large portion of the leaf, and only a few leaves per plant are usually involved. Likewise,feeding and egglaying punctures probably have little effect on plant vitality.