People who bring their plants indoors in the fall often complain about the tiny “fruit flies” that might come along too. These are most likely fungus gnats although anyone plagued by gnats should check to see if the problem is really coming from their drains.
Fungus gnats are annoying, but they don’t bite people. The larvae feed on decaying plant matter, roots and the organic material in potting soils. Fungus gnat larvae are typically in the top few inches of the potting soil, and letting this dry between waterings can help a bit as they prefer living in moist environments.
I’ve found that a two-pronged, organic strategy is best for controlling this pest. To trap the adults I hang up yellow sticky-cards, aka White Fly Traps or Insect Monitors. Since most insects are attracted to the color yellow the adult gnats fly to these and get trapped.
To kill the larvae in the soil I add spinosad to the watering can for about three weeks after my plants come inside. You could also use Bt. Both of these are organic controls for larvae, but you’ll want to use this at least three times in order to kill off successive generations.
Watering plants with spinosad just before you bring them inside in the fall, and putting the sticky cards in place immediately, will help prevent you from being bugged by these pesky gnats.
You can hang yellow sticky cards using a twist-em tied to a bamboo stake, but I find it easier to use an old fork to hold them. Put the card in the tines and and stick the handle into one of your pots.
