Sorghum Midge

Pests of Field Crops in Southern Africa

SORGHUM MIDGE

(Diptera: Cecidomyiidae)

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Text Box: On occasion, late-planted sorghum can be attacked by a small fly, Contarinia sorghicola, which lays its eggs on the heads during flowering. The flies are about 2 mm long, have long legs and a dark orange abdomen. The damaging stage is the maggot, which is tiny, but bright orange in colour. TOP

Text Box: Cultivated and wild species of Sorghum are the main hosts, with an indigenous grass (Andropogon) being recorded as an alternate host. TOP

Text Box: Although serious attacks by this pest seem to be rare, in a heavy population there may be one larva per spikelet in the head, and this density is sufficient to result in the development of little or no grain. Infested heads may have a flattened appearance with shrunken seeds, and close inspection reveals the orange maggots and their pupal cases still attached to the heads. Infestation by the midges can only take place during flowering, and attack is usually most serious in late-planted crops in the lower-lying, warmer areas. TOP

Text Box: Eggs are laid singly near the spikelet tips while the crop is flowering. Each female can lay up to 130 eggs in her lifetime, which is no more than a few days. The larvae move down and feed on the developing seeds, taking up to 11 days to reach maturity before pupating. They either pupate without a cocoon in the warm weather with the adults emerging in less than a week, or construct a cocoon in which to hibernate in cooler or unsuitable conditions. TOP

Text Box: Chemical control of this pest is difficult and does not tend to give complete control. It is far more reliable and more cost-effective to plant the crop early (before the middle of November) to avoid serious attacks. TOP

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Sorghum midge on sorghum spikelets. (Photo: A N Sparks Jnr. Univ Georgia. Bugwood.org)