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Managing Biting Midge.

There are over 4,000 species of family Ceratopogonidae, the family of biting midges.  Of the 11 species in South East Queensland there are five species which are major pests.  Each species has a different breeding habitat.

Culicoides subimmaculatus:  breeds in open mangrove areas.   

Culicoides marmoratus:  breeds in algae covered mud in salt marshes or below mangroves.  

Culicoides ornatus:  breeds in tidal creeks associated with the Brisbane River.  Active dawn and dusk only.

Lasiohelia townsvillensis:  traditionally breeds in rainforests, but now occur in urban situations where rainforest conditions are mimicked by well watered gardens with mulch, compost heaps etc. Generally appear after heavy rains, and early winter rain may lead to an outburst in spring.  This species is known to bite all day.

Culicoides molestus:  formerly found in estuarine areas where it was not classified as a major pest species.  Canal developments created an ideal habitat for this species.  The soft flocculated sand is an ideal place for the female to lay eggs, and the proximity of the human and dog populations provide a ready supply of blood meals.  Emergence of females begins 3 days before full or new moon, 50% emerge by the next day and emergence is completed on the day of the full or new moon.  Although the flight range is only 400 to 500 metres it has been found much further from any possible breeding place.  It has become a major pest of residents in canal estates.

Description and Life Cycle

Biting midges are very small, 1-3mm long.  Typically they are greyish, but more reddish when filled with blood.  The mouthparts consist of four minute cutting blades (that lacerate the skin inflicting sharp burning pain), enclosed in a fleshy sheath.  The eggs are roughly banana-shaped, with rounded ends and a surface variously adorned with minute projections.  They are rarely encountered in nature and are laid in batches of up to fifty in or near the larval habitat.

A tiny worm-like larva hatches and is the main feeding stage of the life cycle.  It grows from first to fourth instar, moulting each time, over a period of days, weeks or months according to species and environmental factors.  The pupal stage looks rather like a tiny legless blunt nosed lobster which breathes air through a pair of small respiratory trumpets at the head end.  It does not feed during this stage.  The adults emerge from the pupa after some days or weeks. If this is cyclical (eg related to tides) it will take place over several days with the males about a day ahead of the females.

Like mosquitoes, the female biting midge takes a blood meal to provide protein to develop her eggs. They are known as pool feeders because they use their proboscis like a saw to create a tiny hole into the skin into which a pool of blood can flow.  Saliva is injected into the pool to help the flow of blood. The direct impact on human health caused by biting midge is due to allergens in midge saliva reacting on people of varying degrees of sensitivity and immunity. Most people find the bites uncomfortable and distressing with the irritation leading to scratching and sometimes infected sores.

Biting Midge Facts

  • Biting midges are found on all continents except Antarctica.
  • Biting midges are extremely annoying but are not known to transmit disease in Australia.
  • Midge harbour (rest) in but do not breed in grass, trees or in soil or sand in the garden.
  • In overcast humid weather, they are known to bite all day and night.
  • Biting midges can detect CO2 from as far as 100 metres.  They also detect body heat and lactic acid generated during strenuous exercise.

Biting Midge Management (compiled from various South-East Queensland Local Government Brochures) What can and cannot be done to address the biting midge problem?

  • Biting midges are amongst one of the most complicated pest species to control and cannot be eradicated.
  • The larvae of midge exist in mud and sandy substrates which makes treatment near impossible whereas mosquitoes breed in water pools making their treatment simpler. 
  • There is currently no registered larvicide for biting midges, as the larvae occur in environmentally sensitive areas of the inter-tidal zone and dispersal patterns are poorly known.
  • The required larvicide dosage would also be environmentally damaging, affecting non targets. 
  • Councils treat mosquito breeding areas on public (and some private) land but do treat midge breeding areas because of the lack of environmentally safe treatments and limited effectiveness.
  • Insecticide application against adult midges is the only option available, however this method provides relatively short term relief and repeated applications are necessary. 
  • Adulticide fogging has limitations on its effectiveness as the mist/fog will only affect what it comes into contact with.
  • Research nearly a decade ago investigated the effectiveness of treating mosquito and midge harbourages in Hervey Bay and Redcliffe.  Biting midge are prone to desiccation in the heat of the day and rest in cool, shady areas such as the underside of leaves of shrubs and under stairs etc.  

Management at your property

  • If biting midges are a problem entering the house, smaller mesh size fly screens should stop entry. Screens can also be sprayed with insecticide to deter midge entering.
  • It is most likely that midge will enter dwellings on the sheltered side of the dwelling. Close windows on that side when midges are a problem.
  • Midges do not like to seek blood meals when a moderate breeze is blowing, so ceiling fans or other fans that increase air flow inside the dwelling may also decrease biting midge nuisance indoors.
  • Mosquito coils or plug in insecticide tablet burners may be useful during periods of severe midge nuisance.
  • Activities such as water hosing and digging soil attract biting midge. Avoid outdoor activities like car washing and gardening during the early morning and late afternoon when midges are most active.
  • Wear light long sleeved clothing when outdoors during midge activity periods, usually early morning and late afternoon, to minimize exposure to these insects.
  • Personal insect repellents applied to the skin and clothing as directed usually give several hours protection. Sensitive individuals or young children not wishing to use commercial repellents can try liberal applications of baby oil to exposed skin to reduce bites. An effective home repellent can be made up with equal parts of baby oil, Dettol and an aromatic oil such as citronella or lavender. Local research has shown that oil extracted from the lemon scented gum Eucalyptus citriodora is also a good midge repellent.
  • Biting midges have a histamine like substance in their saliva which can cause intense itching in sensitive individuals. To prevent acute allergic reaction and allow the body to develop its own immunity to midge bites vitamin B1 (thiamine) can be tried. This vitamin has an anti-histamine type action. Biting midge expert, Dr. Eric Reye, suggests an adult dose of 200mg twice a day with meals, preferably starting 2 weeks before exposure to midge. As immunity is developed this dose can be reduced. The development of personal immunity generally comes with a regular exposure to low numbers of midge bites, not occasional heavy exposure. Persons who have a more acute reaction to midge bites may require anti-histamine drugs at times. You should consult your family doctor before trialing these drug therapies.
  • Insect trapping devices using ultra violet light as the attractant are generally useless for decreasing biting midge numbers in suburban yards. Traps using carbon dioxide as an attractant must be well designed and operated as well as strategically placed to have any possible beneficial effect.
  • As biting midges are biologically linked with the lunar cycle, take note of the lunar period when midges are most active in your area. If for example you live in an area affected by Culicoides molestus, this species bites most actively in the few days following the full and new moon, so planning an evening barbecue around this time during the warmer months would not be wise.

Either:  Keep vegetation surrounding the house to a minimum. This reduces insect harbourage areas and increases air flow around the house. Also keep lawns well mown as any activity that reduces sheltering sites and lowers humidity surrounding the house will help to deter midges. Landscaping with tallish vegetation with an upper tree canopy is preferable to low, dense vegetation in midge prone areas as it allows a much better airflow near ground level.

Or:  Synthetic pyrethroid harbourage sprays, applied around vegetation and exterior walls may substantially reduce midge adult numbers around treated premises for many weeks.

Research around Hervey Bay and Redcliffe nearly a decade ago investigated treating mosquito and biting midge harbourages.  This treatment may reduce midge numbers for up to six weeks though not totally eliminate the pest. The pesticide is applied to shrubs, foliage, fences, house walls and screens – anywhere where midge may harbour.  Licensed pest managers treat harbourages using a product based on bifenthrin, a synthetic pyrethroid.  This chemical is indiscriminate and will kill most other insects over the six-week period that it is active. It should not be applied to plants that are in flower and attracting other insects.  Care must also be taken to ensure the spray does not drift into waterways.

The best results are obtained when neighbouring properties are also treated and a programmed treatment cycle for the ‘midge season’ is followed.