The Q&A Archives: fungus gnats

Question: what can i do to get rid of these pest, i let dry out , uesd a soil drench and spray, sticky traps and when i think they are gone and slightly water my plants again they are back! ive been fighting these pest for about 6 months... i even changed dirt and washed out old dirt and within days they are in the new soil.will sand over the topof the soil work and do i have to change soil again???? help me....

Answer: These tiny little pests feed and breed in moist organic matter. Since they fly, they're hard to control with chemical sprays but you can get rid of them by simply placing a barrier between the potting soil and the pests. A layer of gravel (aquarium gravel comes in lots of pretty colors) would be a great way to create a barrier. A half inch of sand might work, as well. Or, you might try spraying the soil with a gnat control insecticide. Repeat applications are sometimes necessary. I've had really good success with plastic wrap. After thoroughly watering the plants and allowing the excess to drain, then dumping out the water tray, I cover the soil with Saran Wrap. Work it up around multiple stem plants (two sheets/pieces are easier to patch little slits or holes). When I've covered all the soil I stretch the plastic wrap over the sides of the pot and it stays. Keep the cover on for 7-10 days and you should be rid of the pests - until another population flies in through the screen or open door! Best wishes with your potted plants!

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