Fungus Gnat

Bradysia spp., Orfelia spp.

Content coming soon for this insect guide.

Insect Profile

Beneficial Rating

-2 Pest

Active Months

JanFebMarAprMayJunJulAugSepOctNovDec

US Distribution

NortheastSoutheastMidwestSouthwestWestPacific Northwest

Habitat Preferences

gardensgreenhouseshouseplantsmoist areas with decaying organic matterpotting soilcompost piles

Taxonomic Group

Fly

Order

Diptera

Family

Sciaridae, Mycetophilidae, Keroplatidae

Lifecycle

Fungus gnats undergo a complete metamorphosis with four life stages: egg, larva, pupa, and adult. The entire life cycle can be completed in as little as 17 days in warm conditions (around 75°F). Eggs are laid in moist soil or organic debris and hatch in about 3-4 days. The larval stage, which consists of four instars, lasts for approximately 10 days. During this time, the larvae feed on fungi, organic matter, and plant roots. The pupal stage lasts for about 4 days, after which the adult gnat emerges. Adults live for up to 10 days, and a single female can lay between 200 and 300 eggs, leading to multiple, overlapping generations each year.

Overwintering Strategy

Most fungus gnats overwinter as larvae or pupae in the soil or other moist organic material. Some species, such as Exechia nugatoria, are exceptionally hardy and can survive freezing temperatures by producing natural antifreeze proteins, allowing them to semi-freeze and reduce water loss during winter.

Native Range

Worldwide

Attracted By

moisturefungidecaying organic mattercompostleaf moldroot hairslight

Repelled By

chamomilecinnamonlavender oilpeppermint oil

Organic Control Methods

Organic control of fungus gnats focuses on disrupting their life cycle and creating an inhospitable environment. A primary method is to allow the surface of the soil to dry out completely between waterings. Physical barriers such as a layer of sand or diatomaceous earth on the soil surface can prevent adults from laying eggs. For larval control, soil drenches with Bacillus thuringiensis subspecies israelensis (Bti) or beneficial nematodes (Steinernema feltiae) are highly effective. Predatory mites (Stratiolaelaps scimitus) can also be introduced to the soil to consume eggs and larvae. Adult populations can be reduced using yellow sticky traps or apple cider vinegar traps with a drop of dish soap.

Companion Planting

No specific companion plants are recommended to deter fungus gnats. However, carnivorous plants such as Sundews (Drosera), Butterworts (Pinguicula), and Drosophyllum can help control adult populations by trapping them. The primary companion planting strategy is to ensure good drainage and avoid overwatering all plants to make the soil less hospitable.