Gnats in Plants

gnats

Fungus Gnats

The pest gnat infesting houseplants is the Fungus gnat. Fungus gnat adults are about 1/8-1/4 inch long, have long, thin legs in relationship to their overall size, are black and have a long, slender abdomen. Larvae are very small, thread-like in appearance and have a whitish body and black colored head. Fungus gnat larvae feed on soil fungi and can cause damage to small roots and root hairs by feeding on those parts of the plant.

What Attracts Fungus Gnats?

Fungus gnats often become a nuisance to homeowners, business employees and visitors to malls and other commercial buildings. Since fungus gnats are attracted to lights, they commonly are seen around doors, windows and interior sources of light. They are known to impact the health of plants when infestations are allowed continue without control. The following are ways that fungus gnats can become indoor pest problems:

  • Overwatering of houseplants that encourages the growth of soil fungus and provides a source of food for fungus gnat larvae.
  • Houseplants that are left outside during the warm weather months become infested, but are not a noticeable problem until the infested plants are brought inside for the winter.
  • A newly purchased infested plant is brought home from the garden center, or a company employee brings an infested plant into their workspace.
  • Gnats enter the home or business through open doors and windows and infest indoor plants.
  • Fungus gnats sometimes lay their eggs in potting soil and become an indoor problem when infested potting soil is used or stored inside. If an opened bag of potting soil is stored somewhere inside, frequently inspect the bag to make sure fungus gnats are not living and developing inside the bag.

Prevention and Control of Fungus Gnats:

  • Do not over water houseplants; let the soil dry to stop fungus gnat develop in the soil. Also, ensure that potted plants have good drainage.
  • Keep the plant’s soil free of organic matter such as shed leaves and other plant parts.
  • Store open bags of potting soil in an airtight container or throw away any infested items.
  • Inspect any newly purchased plants or plants that have been outside before bringing them inside
  • Eliminate water leaks and poorly draining downspouts and gutters since fungus gnats do well habitats such as these.
  • Inspect compost piles to make sure they are not creating fungus gnat developmental sites.
  • Repair or replace damaged screens before the onset of the fall months since fungus gnats are more likely to come inside at the end of the warm, summer months.
  • Use yellow, sticky card fungus gnat monitors to trap adults infesting indoor plants. Fungus gnats are attracted to these monitors and will get stuck to the card and die.
  • Consult your pest management professional (PMP) regarding his or her recommendations for using insecticides to control fungus gnats. These experts are able to provide a correct identification and effective advice to resolve fungus gnat problems.