Within a few weeks of repotting my orchids (phalaenopsis) they were infested with small black flies. The flies are very small and seem to die off after a number of days.To try and control the pests I disposed of the ‘infested’ potting compost and repotted the orchids in a new compost. Before repotting I washed the leaves and roots with water. Unfortunately the flies came back after about two weeks and have multiplied rapidly.Can you suggest any insecticides that should be used? Should I repot the plants again but this time wash the plants with insecticide?
Simply reduce watering. Allow the comost to become slightly dry on top before watering. The flies that have appeared may have come from other pots that are similalry too wet.