Fungus Gnats - A Pest in Potting Soils
The Fungus Gnat, Orfelia and Bradysia species, are small flying insects that have a life cycle similar to that of the common house fly. The adult flies are very small and lay their eggs in organic material such as potting mix or other similar rotting garden material.
If these eggs are laid in a container in which gerbera plants are growing, when the larvae hatch, they will burrow their way down to the plant's roots and crown tissue and live off the plant's goodness. The affected plant will appear listless and and lacking vigour and will look like it needs water. However, the larvae are almost impossible to see with the naked eye. If you are checking the roots of the plant for an infestation, use a magnifying glass.
Adult gnats can be caught thorough the use of sticky yellow traps and there are a number of commercially available pesticides that will destroy the larvae.
Gerbera growers have discovered that adding a small quantity of powdered wetting sulphur to the potting mix or soil is an affective control measure.