also feed on plant roots, which may cause problems with
seedlings and cuttings. Mature plants are less likely to be
affected, unless the fungus gnat population is extremely high.
You can repot
plants into fresh potting soil, which will get rid of existing
eggs and larvae. Covering the soil surface with a layer of sand
discourages egg laying by adults. Avoid overwatering, and do not
allow plants to sit in saucers filled with runoff water.
Techniques with Gnats
allow the soil to dry out pretty thoroughly between waterings.
Never take it to the point where the plant wilts, though. Fungus
gnat larvae require a moist environment and may die if you can
allow the soil to dry out thoroughly.
Controls like Bt
There is a
Bacillus thuringiensis (Bt) formulation sold under the name
Gnatrol that controls fungus gnat larvae. It is used as a soil
drench. Ultra-fine horticultural oil may be sprayed on the
foliage to control the adults. Bayer Advanced All-in-One Potting
Soil contains the insecticide Merit (imidacloprid) that is also
labeled to control fungus gnats. You can use it when you repot
the plants instead of plain potting mix.
Sandy's Garden FAQ
Q. I saved
seeds from some of the annuals I grew in my garden this summer,
including four-o'clocks, castor beans and marigolds. What is the
best way to store them?
Once the seeds have dried, place them in an airtight container,
such as a film canister or small jar. You can add a packet of
silica gel -- those packets that come in new shoes or electronic
equipment. Then store the jar in your refrigerator for the