How can I get rid of gnats in plants? What are soap sprays? Can a Schefflera be rooted?
Flying adult fungus gnats only live for about a week before dying of old age. However, the larvae or eggs live in the top layers of the soil where they develop wings and eventually fly out to annoy you. So the key to eradicating fungus gnats is getting rid of the larvae.
Larvae are introduced through contaminated potting soil. Folks that repot their plants often introduce the gnat larvae when they use bagged potting soil. But do NOT decide to wash all the soil away. That will eliminate the larvae, but it will also damage the roots and kill the plant. The larvae feed on decaying rotting matter. That is created by soil that is kept too wet and roots that rot as a result.
First, remove all loose soil from above the roots. Then, allow the soil to dry as deep into the pot as the plant can stand before wilting. The drier you keep it, the more larvae you will kill by dehydration. When you do water, apply just enough so that the soil gets very dry again in a week or less. You do not need any pesticides or soap sprays to treat the larvae.
Soap sprays are a solution of liquid soap and water that are sprayed on foliage to treat some insect pests, such as spider mites. They are not effective with fungus gnats.
Short tip Schefflera cuttings can be rooted in plain water or in small pots filled with damp soil. Thicker stem cuttings require air-layering which I do not recommended unless you are experienced with plant propagation.