Meromyza americana

1. Symptoms: When young tillers are attacked in the fall or early spring, the tillers usually die; infested plants show the "white head" condition typically produced by stem-boring insects (picture at left). The adult flies are about 6 mm in length, and pale green to yellow with dark stripes.
2. Life Cycle: Wheat stem maggot larvae overwinter in cereal plants or grasses (picture at right).The females lay small white eggs, one per stem, near the sheath of the flag leaf; the larvae burrow into and consume the interior of the stem, killing the upper part of the stem and the spike. There are normally three generations per year; one in the spring, one in the summer, and a third in the early autumn that overwinters as larvae.
3. Hosts/Distribution: In addition to wheat, host crops include rye, barley, and other grasses. There are a number of other flies in various parts of the world that attack wheat in a similar fashion and produce the same kind of damage.
4. Importance: In infested fields, 10-15% of plants may be injured. Damage can be severe in some years, but the insect seldom causes widespread damage. However, heavy infestations of individual wheat stands may kill a significant portion of the tillers.