Fungus Gnats

Info for the Indoor Gardener




The first step in eradicating fungus gnats is identifying them correctly. The second step (and third...and fourth...) is to take appropriate, responsible action. These are one of the most common garden pests the Indoor Gardener will eventually face, especially if you don't let your soil dry out between waterings. Read below to learn how to avoid them, find them, and get rid of them.

DESCRIPTION

  • fungus gnats are tiny - about 1/10 - 1/8 inch
  • black or grayish
  • looks like flies
  • single pair of transparent or light gray wings
  • long legs like mosquitoes
  • antennae - often longer than their heads
  • fly, crawl, jump along the planter's surface
  • eggs are oval, smooth, shiny white or transparent
  • larvae - legless, white, shiny, black heads
  • can see through the larvae to the food in their stomachs
  • pupae - silk-like cocoons in the soil


LOCATION

  • adults on the soil surface
  • larvae and pupae in top 1/4" or so of soil
  • fungus gnats love wet soil that doesn't dry between waterings


MULTIPLICATION

  • female can lay upwards of 100 eggs in the week of her life
  • eggs laid in rows in soil
  • larvae grow in rich soil


DESTRUCTION

  • adults to minimal destruction to plants
  • fungus gnats can drive the indoor gardener crazy by being such a nuisance in the air around the plant
  • they multiply quickly and fly throughout your home
  • larvae can eat root hairs and deplete the plant's energy
  • adults can spread diseases from plant to plant


DETECTION

  • you'll notice small fly-like insects close the soil
  • you'll see them - especially around windows, try to swat them, and eventually swallow these garden pests as they multiply from room to room
  • examine soil surfaces as you check your plants regularly
  • notice insects that jump from the soil surface as you water
  • plants wilt, poor growth, loss of leaves, yellowing


SOLUTION

  • easy
  • insecticidal soap: spray on soil
  • let soil dry and then spray again
  • remove top soil to 1/4 inch; add new soil
  • be sure to let soil dry between waterings
  • if you move plants from outdoors to indoors you may want to change the soil; at least the top half inch
  • get rid of dead leaves, twigs, etc. immediately
  • yellow sticky cards (for adults); check and replace every other day
  • pesticides: pyrethins, pyrethroid insecticides (used frequently) for adults; organic Bacillus thuringiensis var. israelensis to soak soil and kill larvae; Neem products
  • chemicals: chlorpyrifos, cyfluthrin, oxamyl, diazinon, resmethrin, among others
  • potato traps for fungus gnat larvae (cut 1-1/2 inch squares white potato; place on soil surface; lift in a few days; discard with larvae; repeat until no larvae found)






For Botanists, Scientists, Outdoor Gardeners, and School Reports


ORDER: Diptera

FAMILY: sciaridae

Bradysia specie Bardysia coprophila (black-winged fungus gnats) Also: Sciara spp., Orfelia spp.

  • adult lifespan = a few days to a week
  • reproduce in decaying organic matter, warm temperatures
  • generation = about a month (egg, larva, pupa, adult)
  • female can lay about 100 eggs in her week of life
  • 3-40 eggs laid in strings around plant base and in cracks in soil
  • eggs hatch in about 5 days
  • "maggot stage" - pale larvae (max 1/4 inch); distinguished by their shiny black heads
  • maggot stage lasts about 2 weeks
  • larva then spins a silk-like cocoon much like a butterfly (pupa stage)
  • generations overlap
  • nutrition from fungi and decaying organic matter in soil, or small root hairs or new roots
  • natural predators of these garden pests: nematodes, predatory mites
  • can spread such plant diseases as: pythium, cyclindrocladium


DISCLAIMER: The Indoor-Gardener.com provides information through data research and personal experience and does not mean to recommend or refute any product used for insect control inside or outside the house. Read and follow instructions carefully as listed Oron all products. Indoor-Gardener.com is not responsible for use of any product or method described on these pages, nor for any possible adverse affects of such use. The legal use of chemicals for plant health can change, and it is solely the responsibility of the user of such chemicals to remain in compliance with such laws. Indoor-Gardener.com and Batya D. Wininger assume no liability resulting from the use of any information on these pages. While this website does its best to provide only the best, up-to-date information to its visitors, there can be changes and mistakes. Read labels carefully and follow instructions for use.



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