Fungus Gnats Integrated Pest Management

Fungus Gnats

Scientific name:

Sciaridae sp.

Image of juvenile larvae

Image of adult gnat

Common name:

Fungus gnat

Insect order:

Diptera

Family:

Sciaridae

Host range:

Fungus gnats do not attack the host plant directly, but rather are attracted to the growing media if conditions are favourable.

Metamorphosis:

Complete metamorphosis.

Life cycle and seasonal behaviour:

Fungus gnats have a life cycle comprising of four stages, egg, larva, pupa and adult. Adult gnats live for approximately one week, laying up to 300 eggs within moist soils during this time. Once laid, eggs can hatch within 3 days. The emerging larvae take 10 days to grow into pupa, and within another 4 days pupa will grow into adult gnats.

Adult mouthparts:

Adult gnats consume only liquids, and do not cause any direct feeding damage to the host plant. They survive 5-7 days, during which time they lay up to 300 eggs within the growing substrate of their host.

Juvenile mouthparts:

Juvenile larvae feed upon organic matter within the host plants growing substrate and will also feed upon their roots if soil conditions have become unfavourable and plant root tissue has begun to decay.

Plant part affected:

Juvenile larvae feed upon organic matter within the host plants growing substrate and will also feed upon their developing root system and stems tissues that are below ground.

Pest management options

Chemical:

Neem oil soil drenches for larvae.

Cultural:

Correct watering practise. Allow top inch of growing media to begin to dry before watering. Growing media that is excessively saturated will attract gnats.

Physical:

Sticky traps are effective at reducing adult gnat populations.

Biological control:

Bacillus thuringiensis subspecies israelensis, Hpoapsis miles mites, Steinernema feltiae predatory nematodes.

Integrated Pest Management (IPM):

Use of yellow sticky traps throughout nursery and garden area to monitor adult gnat populations. Set threshold guidelines for IPM.

Adult fungus gnats are attracted to moist environments, rich in organic matter. Avoid overwatering your plants by practising the correct watering schedule for the requirements of each different plant variety being cultivated.

Neem oil soil drenches can be used to control larvae populations, which build up rapidly within a moist environment.

Beneficial predatory insects such as Hypoapsis miles and Steinernema feltiae will both feed upon fungus gnat larvae and can be very effective in their overall population control.