Corn Blotch Leaf Miner
Agromyza parvicornis
Description
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.
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.
Damage
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.