The adult fly looks similar to a bush fly but is hairier, more slender and has greyer wings.
Has delicate hairy wings
legs . 6
Abdomen - 10-11 segments.
Larva has no legs and looks like a small maggot from 1-7mm long and up to 1mm wide. It is thickened at the rear end and tapers toward the head. It is cream in colour with brown chewing mouthparts. The move by wriggling and are often seen with their back end attached to the root while they wave their front around.
Eggs are laid in the soil near decaying residues and the larva hatches to burrow into a suitable seed of seedling and start eating out the centre of the plant. In 3-6 weeks the maggot pupates in the soil. 2 weeks to 4 months later depending on conditions the adult fly emerges from the pupa and digs its way to the soil surface.
Origin and History:
Damage caused by the maggot attacking the roots of seedlings of lupins, peas or beans. 1-2 leaf seedlings begin to wilt and die and when removed from the soil their roots are grey and mushy with maggots inside. Germinating seeds may also be attacked and not emerge. Maggots may burrow up the stem to the cotyledons. Damage seems to be worse in years with early continual rains leading to damp warm conditions. Large quantities of rotting organic matter from retained stubbles or pasture residues are associated with greater damage.
Management and Control:
Control is very difficult after seed has been planted. Seed dressings or soil applied chemicals before planting may be useful.
Early cultivation, late seeding and elimination of decaying plant matter reduces the incidence. Higher seeding rates can compensate for plant losses under light infestations. In many cases crops are resown after a bean root maggot fly attack and don't suffer a further attack.
Zeuxidiplosis giardi (introduced to control the weed St Johns Wort).
Flies and midges. Sorghum Midge
WADA. Insects and Allied Pests of Extensive Farming. Department of Agriculture - Western Australia Bulletin No. 4185. p37.
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