Dr Cameron Webb (pictured), medical entomologist and author of A Guide to Mosquitoes of Australia, shares his insights on how best to control our most aggravating summer pest.
If you don’t know your pests, how can you expect to effectively control them? It’s one thing to know mosquitoes are a problem but it’s a trickier task to understand what type of mosquito is the cause for concern and how its unique biology may offer clues to better pest control options.
There are over 300 different types of mosquito found in Australia and although only about a dozen cause problems for people, each can bring a range of challenges when it comes to control. Where they’re found, what triggers their hatch, the animals they bite and how far they fly are all considerations when it comes to controlling mosquito pests around the home, workspace or local parklands.
Mosquitoes are simple creatures but they have a complex life cycle. All mosquitoes need free-standing water. Eggs are laid on or near the water and when the immature stages hatch (commonly known as wrigglers) they can take anywhere from a week or many months to complete their developed before emerging and flying off as adults.
Where they lay their eggs can vary. It’s often very specific to the type of mosquito. From coastal tide-filled wetlands to backyard water-holding containers, each mosquito has its preferred habitat. In urban areas, drains, roof gutters, pot plant saucers and bird baths are all prime locations
for the Australian backyard mosquito Aedes notoscriptus and, in far north QLD, the Yellow Fever mosquito Aedes aegypti.
Rainwater tanks can pose a particularly productive habitat and ensuring the tank is properly secured to household infrastructure and any openings are suitable screened, mosquitoes shouldn’t move in. Probably the most problematic habitats are those of plastic buckets, discarded tyres, accumulated bottles and cans, and tarpaulin-covered boats or trailers. When filled with rainwater, these habitats can pump out mosquitoes at astonishing rates!
If you cannot dump, drain or cover up these water-filled containers, try using a methoprene-based control agent or a monomolecular film to interrupt their life cycles and reduce local mosquito populations.
While most mosquitoes need blood, not all mosquitoes will bite people. Some mosquitoes found in Australian wetlands will prefer to bite birds and some even bite frogs and reptiles! While a nutrient-rich blood meal will assist the female mosquitoes developing eggs, it is also a pathway for pathogen transmission. For Australia’s most common mosquito-borne disease, caused by Ross River virus, mosquitoes will pick up the virus from biting local wildlife, particularly kangaroos and wallabies, before passing it onto people. This means that where urban areas are close to bushland or wetlands areas, where both mosquitoes and wildlife are common, mosquitoes can cause more than just a nuisance-biting problem.
Although mosquitoes are small and seemingly fragile insects, some can fly long distances. The mosquitoes found in coastal wetlands, especially the saltmarsh mosquito Aedes vigilax, has been recorded as flying over 20km! This means that mosquitoes causing a problem in backyards or local parklands may actually be flying in from wetlands many kilometres away. For those mosquitoes found in our backyards, they fly much shorter distances, probably no more than 200m. This is still important as no matter how clean, tidy and ‘mosquito habitat free’ you keep your backyard, mozzies from your neighbours or nearby wetlands can still create problems.
If mosquitoes are a problem, and they’re clearly originating from habitats away from the property, the use of insecticides will often be required. Residual insecticides, such as synthetic pyrethroids, can be useful in reducing the activity of mosquitoes around a property but they must be applied in areas where mosquitoes are seeking refuge. Indiscriminate spraying may not be as effective and will definitely impact other local insects. Try applying the product in dark, cool areas where mosquitoes may be hiding out during the day.
If all else fails, or you’re out and about during summer, you can always use topical insect repellents. Formulations that contain DEET, picaridin or ‘oil of lemon eucalyptus’ will all provide protection from bites if you apply evenly across exposed skin. Plant-based products work too but you’ll need to apply a little more regularly to stay bite-free.
More about mosquitoes.
Dr Cameron Webb is the lead author of A Guide to Mosquitoes of Australia (CSIRO Publishing). Follow him on Twitter or Facebook (@mozziebites) to stay up to date on the latest mosquito news and research.
To learn more about mosquitoes and their control, make sure you register for the Mosquito Control Association of Australia conference being held 2-5 September 2018 at Peppers Salt Resort & Spa, Kingscliff, NSW.
This meeting will be of great interest to both local government and non-government staff involved in mosquito control as it will provide an opportunity to network with both industry representatives and mosquito control academics, and a chance to pick up tips on the latest research and emerging technologies.
For more information visit the MCAA website.
Dr Cameron Webb, Medical Entomologist with NSW Health Pathology and the University of Sydney