Biting midges (commonly called sand flies) are from the family of insects known as Culiocoides. There are over 270 species of Culiocoides in Australasia with three main species causing annoyance to humans. Culiocoides spp (nr subimmaculatus) is widely distributed, Culiocoides ornatus occurs in areas north of Tin Can Bay in Queensland, and Culiocoides molestus occurs in canal estates. These pests all have marine associations and are not known to transmit any diseases to humans. Barmah Forest virus has been isolated from Culiocoides marksi but this species rarely bites humans.
Why are biting midge bites so unpleasant?
The anatomy of their feeding mechanism means that (unlike mosquitoes) they leave a large raised mark on the skin that is filled with damaged tissue and saliva (containing anticoagulants). This can cause certain individuals repeatedly exposed to their bites to become “sensitised” and trigger allergic responses. The direct impact on human health and wellbeing caused by midges is due to the allergens in midge saliva. These biting insects are an annoyance to humans, but are not likely to transmit disease.
Biting midges become a public health issue when residential property developments occur close to midge-breeding sites resulting in increased human – midge interaction. The biting midge problem within the Byron Shire community has not been quantified.
What are biting midges?
Biting midges are insects that breed in wet soils in the tidal zones such as mangrove mud and sandy shores. These insects are also important components of our valuable estuary tidal marsh and mangrove ecosystems. Biting midges are attracted to human habitation and rest on screens, fences and vegetation while waiting to take a blood meal. As the biting midge is small and easily blown about by prevailing winds, they prefer dull still days with high humidity when seeking a meal.
There are four species that have been identified as the main cause of midge problems in the North Coast of NSW. They are Cullicoides molestus, Cullicoides subimmaculatus, Cullicoides longior and Lasiohelia townsvillensis. Further information can be found by accessing the Tweed Shire website.
Council recognises the expertise and considerable experience of Tweed Shire entomologist Mr. Clive Easton who compiled the information referred to in the previous paragraph.
At this time council has no data on the extent of breeding sites, the particular species involved and size of this problem in Byron Shire. The use of any pesticides in such sensitive ecological environments is also not supported as it is highly likely to cause serious environmental harm.
No effective treatment process exists to prevent these insects breeding and travelling to the nearest “blood meal”. Some species can travel up to three kilometres from the breeding sites in search of a “blood meal”. The best remedies for such pests appear to be to keep residences from being located close to breeding sites. Only topical repellents and screening of buildings can provide a measure of protection to humans already located in affected areas.
The issue is primarily one of planning, and the inherent conflicts between humans and the natural environment.
A sensible precaution to prevent biting insect attack is to avoid areas that are known to have high biting insect activity. Extensive areas of mangroves or estuarine areas with sandy beaches are potential sources of sand flies and generally residents within 400m of the breeding area can be exposed to them.
There can be a downside in living in a beautiful area like Byron Shire, for example for people who want to work or relax in our beautiful outdoors. This downside includes the nuisance factor associated with midges.
The growing demand by Australian residents to reside in coastal areas has put pressure on land for housing and many areas have been developed near midge breeding sites.
The Biting Midge (Sandflies) Life Cycle
Biting Midge Life Cycle
Like mosquitoes, the female biting midge takes a blood meal to provide protein to develop her eggs. 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 midges are not known to carry any diseases affecting humans in Australia.
There are three major pest species of estuarine breeding biting midge affecting coastal areas. There are also a forest breeding species which seasonally affects other areas of the Shire.
How to reduce biting midge annoyance
Following are some suggestions to help alleviate or minimise midge problems.
- Keep vegetation surrounding the house to a minimum. This reduces insect harbouring areas and increases air flow surrounding 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.
- If biting midges are a problem entering through fly screens, smaller mesh sizes should stop entry. Screens can also be sprayed with the newer low toxic surface sprays containing synthetic pyrethroids to deter midge entering.
- It is most likely that midge will enter dwellings on the leeward or sheltered side of the dwelling. Close leeward windows or keep openings small when midges are a problem.
- As midges do not like to seek blood meals when a moderate breeze is blowing, ceiling fans or other air circulation devices that increase air flow inside the dwelling may also decrease biting midge nuisance indoors.
- Mosquito coils or plug in insecticide tablet burners may be necessary 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.
- 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.
- Wear light long sleeve clothing when outdoors during midge activity periods, usually early morning and late afternoon, to minimise 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 trialling 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.
- Synthetic pyrethroid barrier sprays, applied around vegetation and exterior walls may substantially reduce midge adult numbers around treated premises for many weeks.
Midges are very active during dawn and dusk, and the problem is most prevalent in suburbs located close to mangroves and inter-tidal zones.
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. In comparison to mosquitoes, poisoning midges does not work due to their required habitats and life cycle.
- The larvae of midge exist in mud and sandy substrates which makes treatment near impossible whereas mosquitoes breed in water pools.
- 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.
- Insecticide applications against adult midges is the only option available, however this method provides only 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. Council does not support the application of any harmful pesticides in or near environmentally sensitive environments.