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Wheat Stem Maggot Damage –White Heads (07/05/18)

Damage from wheat stem maggot (Meromyza americana) is high in some areas of ND, southeast and southwest, with >25% incidence of white heads in fields.

Wheat Stem Maggot Damage –White Heads

Damage from wheat stem maggot (Meromyza americana) is high in some areas of ND, southeast and southwest, with >25% incidence of white heads in fields. A single maggot (larva) is located inside the stem just above the last node. As a result, the plant stem pulls out very easily, since the larva chews and cuts the stem. This damage results in empty heads with no developing grain seeds.

The principal cultivated crop hosts of the wheat stem maggot are hard red spring wheat, durum wheat, rye and barley, with wheat being preferred. Further south in Nebraska, wheat stem maggot has recently caused problems in field corn planted after cereal cover crops (Source: Justin McMehan, UNE). It also attacks wild grass hosts including bluegrass, timothy, quackgrass, slender and western wheat grass, wild barley, bromegrass, green and yellow foxtail and bluestem.

Life cycle: Wheat stem maggot overwinter in the larval stage, inside the lower parts of grass stems. In the spring, the larvae pupate and adults emerge in June. The adults are yellow flies, about 1/5 inch long, with three conspicuous black stripes on the thorax and abdomen, and bright green eyes. After mating, females deposit their eggs on the leaves or stems of grasses. The young maggot crawls down beneath a leaf sheath and tunnels into the stem. The stem is partially severed causing the head to turn white. The larva pupates within a cigar-shaped, pale green puparium. The adults emerge about midsummer and lay their eggs on wild grasses or volunteer grain. The resulting larvae overwinter in the stems of the wild grasses and volunteer grain. There are no current guidelines for scouting or action thresholds for wheat stem maggot.

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Janet J. Knodel

Extension Entomologist

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