How to Get Rid of Plant Flies
We fill our homes, window sills, and end-tables with interesting plants. We enjoy walking past our domestic jungles and feeling like nature is part of our lives – and then the invasion occurs. Clouds of tiny gray specks swarm the foliage and leaves get yellow spots and wilt. The SOS goes out: “How do I get Rid of Plant Flies?”
First, what is a plant fly? If you can identify the flying pest, you can decide the best method to rid yourself of them.
Fruit flies are small (1/8″) and tan with red eyes. Phorid flies are tiny, less than 1/8″ long, dark brown or almost black. They move in a nervous, hectic way. Fungus gnats look like tiny mosquitoes. These flies feed and breed on moist organic matter like wet, organic soil in potted plants and on cut flowers.
Whiteflies look like miniature moths (see more on how to get rid of moths). They lay their eggs on the leaves of plants. They feed by piercing the leaves and sucking out the sap. Look for whitefly nymphs attached to the underside of leaves. Whiteflies excrete a substance called “honeydew.” Look for slightly sticky, shiny spots on the tops of the leaves.
Once you have identified the bug living in your philodendron, you can decide how to get rid of the plant flies. The difference in where the flies breed and how they feed influences the best method to get rid of them.
Always check plants carefully before you introduce them. Look for the insects themselves and for any signs of insects: honeydew, yellow spots, white “bumps” that might be eggs. Use sterile potting soil when you transplant or re-pot your plants so that you don’t bring fly eggs into your home. Don’t over water your plants. Flies like wet soil.
Adult plant flies can be killed with sprays containing pyrethrin or permethrin. These products will be labeled for “gnats” or “flying insects.” Always read the label and follow directions and safety precautions.
Oil Soap Spray
Insecticidal soap and horticultural oil sprays can be an effective, less toxic remedy for getting rid of plant flies on indoor plants. You must cover both the tops and bottoms of the leaves as well as the surface of the soil.
Plain soapy water will work too. Take your plants outside on a warm day, put them in a shady spot and hose them down with soapy water. That will kill most of the adults and wash off whitefly eggs.
Cleaning off the leaves will kill whiteflies and many of their eggs but it only kills the adult phorid flies and fungus gnats. To kill the larvae and destroy the eggs you must get rid of the infested soil. Report all of your treated houseplants at once with sterile potting soil in cleaned pots. Rinse as much of the soil off the roots as possible. This method is stressful for the plants and laborious for you. It is unnecessary work if the only bugs you have are whiteflies. You may want to reserve this method for severe infestations of fungus gnats or phorid flies.
Enjoy your private tropical jungle without the insects. Proper sanitation, soil and watering practices will keep the plant flies at bay.
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