Contarinia tritici

Scientific Name Contarinia tritici (Kirby)
Common Names English: Yellow wheat blossom midge; German: Gelbe Weizengallmücke; Spanish: Cecidómido amarillo del trigo; French: Cécidomyie jaune du blé
Description The adults are 2-3 mm (0.078-0.12 inch) long and yellow, with black eyes; the larvae are flattened and lemon-yellow.
Distinguishing between C. tritici and Sitodiplosis mosellana (orange weed blossom midge) is sometimes difficult. The latter has orange larvae which emerge later and, as the eggs are laid separately, there tends to be only one larva per floret.

Biology

Damage

Shortly after ear emergence, groups of about 4-8 lemon-yellow larvae are found in the florets, feeding on the ovaries, and thus impairing the development of the affected grains. The remaining grains often appear deformed, and sometimes their glumes will show dark-brown stains.

Lifecycle

In early summer, on warm, windstill evenings around the time of ear emergence, the females lay their eggs in groups of 8-10 inside the flowers, between the glumes. The larvae feed for several weeks and normally leave the ears in July, before harvest. They drop to the ground, burrow themselves into the soil, and form cocoons, in which they overwinter. A proportion of them will spend two or more winters in diapause.
In May or June, the larvae leave their cocoons, move nearer to the soil surface, and pupate. After about two weeks, the next generation of adults emerges. These only live for one or two days.
In some years, a second generation appears in September on weed grasses, but it does not complete development. Due to the ability of the larvae to hibernate twice or even more often, it is not easy to predict the severity of infestation in an upcoming season.

Occurrence

Additional Crop Information

Seldom on rye or barley.

Agricultural Importance

Normally, the yellow wheat blossom midges only appear in comparatively small numbers, but under favorable weather conditions, mass outbreaks are possible, leading to substantial yield losses. Besides a reduction in yield, the damage leads to the corn having reduced milling and baking quality.

Control

Integrated Crop Management

Regular crop rotation can reduce the midge population.

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