I've never had gnats thankfully. But the general consensus i see is that getting natural predator mites that eat the larvae of the flies is the way to go heres some interesting info
Hypoaspis aculeifer – Predator mite
Hypo-Mite™ is a soil-dwelling predatory mite that feeds on fungus gnats (mycetophilids, sciarid flies) and other insects, mites and nematodes in soil and growing media.
Hypo-Mite™ is known to be useful in greenhouse vegetable and ornamental crops, including bulbs, as part of an integrated pest management programme.
The Pest – Fungus gnats
Fungus gnats are small, dark, two-winged flies with long legs similar to mosquitoes. Adults are approximately 3 mm long and are weak, erratic fliers. They are more prevalent in greenhouses, but may also become numerous outdoors.
The larvae of fungus gnats are white or transparent and are legless, and have a shiny black head. They are usually found just below the soil surface in association with decaying plant material, moss and algae.
The life cycle of fungus gnats takes approximately 25 days at temperatures above 20 °C.
Ideal conditions for fungus gnat outbreaks are high humidity, high soil or growing media organic matter, water-saturated soil or growing media, presence of moss and algae and decaying plant material.
Fungus gnat larvae cause damage to plants by feeding on the roots. Fungus gnats can also spread plant fungal disease throughout a greenhouse on adults, and by larvae through the soil.
Signs and symptoms of fungus gnats include:
- Plants lack vigour and leaves may turn yellow
- Small brown scars are evident on roots, and root hairs are eaten off
- With heavy larval infestations, plants can be weakened severely and die
The Solution – Hypo-Mite™
Hypo-Mite™ is a small pale brown mite with a distinct V-shaped dorsal shield. Adult mites are 0.5-1.0 mm long and are commonly found in the top few centimetres of soil or compost.
Females lay their eggs near the soil surface, and these hatch into six-legged larvae. There are two further nymph stages and a life cycle can be completed in 10 days at 25 °C, but can vary from 7-30 days depending on temperature.
Below 12 °C, Hypo-Mite™ becomes inactive, and development stops when temperatures fall below 8 °C. The species does not hibernate (diapause) and is able to survive for 6-8 weeks without prey by feeding on decaying organic matter.
Hypo-Mite™ uses its saw-like mouth parts to puncture and slice prey tissue which is then sucked up leaving a shrivelled prey body. They prefer feeding on younger fungus gnat larvae, and adults can consume 1-5 prey per day. Both adult and immature Hypo-Mite™ are predatory.
Hypo-Mite™ is also a predator of thrips pupae in the soil, however, alone they do not provide sufficient control of thrips.
Hypo-Mite™ is not considered harmful to humans or animals, and no environmental effects are expected.
Environmental Conditions
Hypo-Mite™ survives well in most greenhouse conditions and is not harmed by regular watering, although flooded or waterlogged areas are not tolerated. Optimum conditions for development are 20-30 °C, and soil temperatures above 30 °C are harmful.
Hypo-Mite™ will survive in most potting mixes, rockwool and perlite.
Release rate
Greenhouse crops: Use 1 litre per 100 square metres, or,
one litre per cubic metre growing media Outdoor crops: Use 20 litres per hectare
Repeated applications may be needed for heavy pest infestations.
Packaging
Hypo-Mite™ is supplied in a mixture of vermiculite and mould as a food source for the mites. There are 10,000 mites per litre of mixture.
Release and Storage Instructions
Hypo-Mite™ need the following handling and treatment:
On arrival, release Hypo-Mite™ as soon as possible
- Hypo-Mite™ can be stored for a maximum of 2 days at 10-15 °C
- DO NOT REFRIGERATE
- Sprinkle the mixture on the soil around infested plants, or incorporate into the growing media before potting-up plants
Post release
Hypo-Mite™ may take 2-3 weeks to exert an effect on pest populations.
Hypo-Mite™ can be hard to find in soil or growing media, therefore monitor pest numbers to determine the need for further releases.
Re-application of Hypo-Mite™ is recommended to ‘hot spots’ should some pests remain.
Before introducing Hypo-Mite™ into your crop please check residual chemical affects and ensure you know chemical compatibilities of products that may be applied.
A list of compatible pesticides and withholding periods can be found in the publication ‘The Good Bug Book’
