The movement of these very small black-bodied flies is more eye-catching than the flies themselves. They are a relatively new phenomenon and are probably associated with the increasing use of peat-based com-
posts. The adults are attracted by peat, especially when it is wet, and they will lay their eggs in it. The small white grubs that hatch then proceed to eat whatever is available—in this situation usually the young, freshly succulent roots of a cutting or seedling.
Most damage is caused when the compost is overwatered, so more eggs are laid and more roots are consumed. Therefore to control infestation of sciarid flies do not allow the compost to be continually soaked. Water little and often.
Chemical control is not easy. The adults because of their mobility are virtually impossible to kill, and control is therefore limited to an attempt to eliminate the larvae. The incorporation of a granular insecticide in the compost will have some effect as a preventative. If an infestation occurs, the best results are achieved by drenching the compost, preferably with bhc .
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