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Stenodiplosis sorghicola (Coquillett, 1899) · formerly or also: Contarinia sorghicola
The sorghum midge is a tiny orange fly that lays its eggs in sorghum flowers just as they open. The maggot feeds on the developing seed so that the floret stays empty, and heavily attacked heads look blasted and chaffy. It is the most widespread insect pest of grain sorghum worldwide, and because one generation takes only about two weeks, staggered flowering across an area lets populations explode.
The scientific name of sorghum midge is Stenodiplosis sorghicola (Coquillett, 1899), in the order Diptera, family Cecidomyiidae.
Older or alternative scientific names: Contarinia sorghicola.
Found in almost every sorghum-growing region: Africa, South and East Asia, the Americas, Australia and Europe.
| Region | Status |
|---|---|
| Africa | Widespread |
| South and East Asia | Widespread |
| Americas | Widespread |
| Oceania | Widespread; a key pest in Australia |
Adults are fragile midges about 1.5-2 mm long; females have a bright orange-red abdomen. Larvae are tiny maggots, colourless at first and later orange, inside the florets. Pupae form inside the floret and leave a white pupal case sticking out of the glumes after the adult emerges.
| Crop stage | What you see |
|---|---|
| Flowering | Swarms of tiny orange midges around flowering heads in the morning. |
| Grain fill | Florets remain empty and chaffy; squeezing them may produce a red smear from larvae or pupae; small white pupal cases at the tips of glumes. |
| Maturity | Heads look blasted with few grains, often on late-flowering heads in a field or area. |
Adults live only about a day. Each female lays several dozen eggs, one per floret, at the time of flowering. The larva feeds on the ovary, then pupates in the floret. Mature larvae of the last generation enter diapause in spikelets and survive in crop residue and soil until the next season. Diapausing larvae can remain in old heads and soil for more than one season, then emerge when early grasses or sorghum begin to flower.
| Stage | Duration | Notes |
|---|---|---|
| Egg (in floret) | About 2 days | Laid in flowering spikelets. |
| Larva (in floret) | About 9-11 days | Destroys the developing seed. |
| Pupa | About 3 days | Inside the floret. |
| Adult | About 1 day | Emerges in the morning, mates and lays eggs. |
A generation takes about 14-16 days in warm conditions; high humidity and moderate temperatures during flowering favour the midge.
Many overlapping generations wherever sorghum and grass hosts flower over a long period.
Staggered sowing and flowering across fields and farms, late-sown crops, Johnson grass and other host grasses flowering nearby, humid weather at flowering, and susceptible open-flowering varieties.
There is no single international numeric threshold. Regional guidance counts adult midges on flowering heads in the morning and relates the count to the expected value of grain and the cost of control; values differ between regions and between resistant and susceptible hybrids.
Thresholds are local. They depend on crop price, control cost, variety and natural-enemy activity, so use the figure your local extension service publishes where one exists.
Yield losses of 10-50% are common where flowering is staggered and susceptible varieties are grown, and late-flowering crops can lose most of their grain. Because each egg destroys a single grain, heavy attacks over several days of flowering can leave panicles nearly empty, and the losses are hidden until heads are examined closely.
Control works best as a sequence: prevent, monitor, then act only when a threshold or a risk forecast says so, using the least disruptive option that works.
Sprays are timed to flowering when adult counts exceed the local threshold, sometimes repeated as new heads flower. What is registered differs by country and changes over time; follow the label and your local plant-protection authority.
| Scheme | Group | Mode of action | Notes |
|---|---|---|---|
| IRAC | 3A | Sodium channel modulators (pyrethroids) | Targets adults at flowering. |
| IRAC | 1B | Acetylcholinesterase inhibitors (organophosphates) | Where registered. |
Grain and forage sorghum and related grasses such as Johnson grass and Sudan grass, which allow the midge to build up before sorghum flowers.
How to grow the crop well is the first line of defence. Laisha's free grow guides cover each crop from sowing to harvest:
Written by Laisha from the sources above, in its own words. This page is general reference, not a prescription: confirm identification locally and follow the label and your plant-protection authority.