Dr Mark Walker from FMC’s Specialty Solutions team shares his tips on how to combat mosquitoes, with advice for ensuring the most effective application of insecticides.
As the weather warms and we get closer to summer, your customers are spending more time outdoors. The increasing temperatures also mean an increase in the mosquito population. Mosquitoes affect personal amenity and they can be carriers of disease, so understandably your customers want them gone as soon as they appear. Attention to application is vitally important with this pest.
There are many factors that will affect the success of your mosquito management strategy, but three factors that deserve attention are: choosing an appropriate chemical formulation and active ingredient combination, knowing the mosquitoes’ habits and biology, and using the correct application techniques for the situation.
Two common types of mosquito control products are larvicides and adulticides. In Australia, the use of larvicides is often carried out by local or state governments in high pest pressure areas. The professional pest controller will often be employed to perform the complementary role of helping property owners deal with adult mosquito control – the focus of this article.
Active ingredients and formulations
When deciding what active ingredient and chemical formulation to use, it’s important to consider the impacts on efficacy, the acceptable use situations and the safety for technicians and residents alike.
Bifenthrin, a pyrethroid, in particular has proven itself to be quite durable and reliable. It is a long used and well trusted option, due to a strong history of efficacy. Performance is even better in shaded and protected areas – the very same sites mosquitoes prefer. This fit has made bifenthrin a very effective tool against adult mosquitoes.
Bifenthrin can be manufactured in different formulations, but a common one is suspension concentrates (SC). SC formulations are effectively solids kept in suspension via formulation components or physical agitation. SC formulations can work very well in mosquito control efforts as the active ingredient is placed on the treated surface and remains quite available to the desired target – in this case the mosquito.
Many bifenthrin products are registered for use in internal and external situations at a low rate. The low water solubility, which is a dominant characteristic of bifenthrin, combined with a strong affinity for porous and organic material, ensures that it will not easily wash off treated surfaces.
This allows it to remain active in outdoor situations between treatments and combined with a comparatively favourable toxicity profile, is why it has had such a good fit in the living environment around properties. It stays where it’s needed for mosquito control, while the non-sensitising properties mean that most people and pets can enjoy the space while it continues to work.
Even though it seems like you’d want a product that is highly irritable to adult mosquitoes to repel them, what is actually needed is a product that allows the mosquito to remain in contact with the active ingredient long enough to absorb a fatal dose – bifenthrin is ideal.
Application techniques
The correct application technique for any chemical used in insect control is incredibly important and mosquitoes can require some extra thinking to get the best results. A critical element to consider is the surface you’ll be spraying, as the type of surface influences the amount of solution needed. As an example, Biflex Aquamax offers guidance to increase the spray volume by a factor of two if applying to a porous surface.
While it’s tempting to use the lowest labelled rate for any job to increase your profitability, it’s not always the right approach. The higher rate should be used when pest pressure is high, or it’s a first treatment and your customers demand maximum protection. Using a higher rate in these circumstances is also one element of a good resistance management strategy. Under-dosing is a sure way to accelerate the presence of individuals predisposed to resistance. Using a lower rate when pest pressure is high will equally result in unhappy customers due a lesser product performance and damage to your brand.
The lower rates can be used for follow-up treatments or as maintenance treatments if the pest pressure remains low. Remember, no mosquito control strategy can guarantee to eradicate all adult mosquitoes so don’t over-promise, but remind customers that regular spraying at the lower rate can keep the pest pressure low and their enjoyment of their amenity areas high.
Another critical aspect of any treatment plan is deciding which equipment is best for the situation. Luckily, many mosquito adulticides can be applied with standard pest control equipment. For example, an SC formulation of bifenthrin like Biflex AquaMax can be applied with power sprayers and most hand-held pumps, making it the perfect choice for most application situations. Note that some product labels do not support ULV or thermal fogging, so read labels carefully to know what is endorsed.
Many insecticides are highly toxic to aquatic life, so be extremely careful around ponds, canals and all waterways. This is where being fully aware of your surroundings is crucial. Knowing what is over the neighbour’s fence or is in adjacent parklands or public open space may influence products used, or equipment employed. A backpack mister provides turbulent air movement, which is great for coverage in dense foliage to treat all mosquito-resting areas. It can however increase droplet travel, which may not be desirable if a sensitive area is in the immediate vicinity.
Be mindful not to over-treat! Many labels recommend applying only to point of run-off, but not so much that it is dripping off the surface. For best results, do not apply during high heat or strong winds and certainly be aware if rain is expected.
Even the best equipment cannot provide the desired results if the spray lines are contaminated with another product or the nozzles are blocked. Always clean your equipment after every use according to the manufacturer’s instructions.
Mosquito biology and habits
Understanding adult mosquito biology and habits will mean your application is the most effective for you and your customers.
Broadly speaking the biting behaviours of adult mosquitoes fall into three distinct times during the day depending on species; diurnal species are active during the day, crepuscular species are active at dusk and dawn while nocturnal species are active during the night. Simply knowing this and aligning with the identity of your target will help determine the most effective treatment times and potential harbourage sites, but it’s also important to remember that temperature, humidity and light all affect mosquito activity greatly. Lower temperatures and lower humidity usually reduces activity.
An effective mosquito control strategy should include internal and external applications on all potential harbourage sites that might be used to escape direct sun, wind or rain. Internal resting sites include walls, fly screens, behind and under sinks, furniture and don’t forget the indoor plants. External resting sites include building exteriors, eaves, walls, fences, garages, sheds, gazebos, ornamental plants, shrubs and any shady and/or damp areas. Try to think like a mosquito to identify all the nooks and crannies they’ll find to hide and you’ll develop a successful treatment plan.
The flight range and dispersal of mosquitoes varies greatly between species with many estimates of range suggested in studies, so consider this with caution. The best approach is to treat all areas on the property that could provide harbourage for any type of adult mosquito, for the most assured results and happy customers.
Summary
Mosquito control has always been challenging in Australia, especially now when recent events have made people even more aware of the diseases they might carry. You can be a hero to your customers by choosing the right chemical for the situation; for mosquitoes you need a product that is non- sensitising, effective and long lasting. You can feel confident that your chosen chemical is given the best chance of working by using the correct equipment, appropriate application techniques and knowing where the pests go to hide.
Dr Mark Walker, Development & Technical Lead, Specialty Solutions, FMC Australasia
