Grain sorghum and Johnson grass are the primary hosts, reported on and reared from 14 other grasses. Larvae of the sorghum midge feed on the ovary, preventing normal seed development.
Infested heads appear blighted or blasted and produce small, malformed grain.
They spin cocoons inside the spikelets where they may remain in a resting stage, resistant to cold and desiccation for as long as 2 or 3 years. Under favorable conditions, however, pupation and emergence take place the following spring at about the time Johnson grass begins to bloom. After mating, each female then deposits 30 to 120 eggs, singly, in the flowering spikelets of this grass. The first two generations of the sorghum midge can be found on Johnson grass, after which a migration occurs to the flowering sorghum spikelets. Newly hatched larvae are colorless but change color as they feed.