Effective mosquito control means choosing the right products to target the problem at the source.
Mosquito control programs may currently be a relatively small segment of the pest control market, but with the changing climate, there is likely to be an increase in demand for mosquito treatments. Increasing rainfall will expand the number of mosquito breeding sites, and warmer temperatures will speed up the mosquito life cycle and extend the mosquito season.
Keeping mosquito numbers down is all about management, and the best way to manage mosquitoes is to target the mosquito larvae and their breeding sites.
Eliminate mosquito breeding sites
Reducing the number of mosquito breeding sites is a standard part of any mosquito management program. Many breeding sites can be eliminated physically at residential and commercial sites. However, it will not always be possible to eliminate all mosquito breeding sites, especially in areas of frequent rainfall, and on large sites or in the natural environment, this is virtually impossible. In such situations, the use of larvicides is the best option and can be very effective in reducing mosquito numbers.
Understanding mosquito larvae
To ensure correct product choice and effective application technique, it is important to understand the basics of mosquito larvae development.
Depending on the mosquito species, the female mosquito lays eggs in various locations in different types of water bodies, from small plant pots for the container mosquitoes, such as Aedes aegypti, to estuarine waterways for mosquitoes like the saltmarsh mosquito, Aedes vigilax. However, all mosquito larvae go through four instars before pupating into an adult. Depending on the nature of the water body and the mosquito species concerned, broods may hatch at the same time (synchronous broods), for example when a dry dam floods, or broods may be continuously hatching (asynchronous broods), as is the case for most permanent water bodies.
This can mean the mosquito larvae present may be at the same stage of development at the same time (in the case of a synchronous brood), or mosquito larvae of all instars can be present all the time (asynchronous brood). With the different mosquito instars having different levels of susceptibility to different larvicides, this information not only impacts the timing of any treatment, but the choice of product.
Which mosquito larvicide to choose?
Two active ingredients are used to treat mosquito larvae: Bti (Bacillus thuringiensis subsp. israelensis) or (S)-methoprene. Bti performs best on first to third stage instars, whereas (S)-methoprene performs best on the late (fourth stage) instars when it prevents pupation.
When using products containing only one of these actives, it requires surveillance of larvae numbers – not just overall numbers, but the stage of the mosquito present, as it is important to apply such products when the larvae are at the appropriate instar for optimal effect. For councils and larger organisations, such monitoring may be possible, which allows the use of these cost-effective products such as the VectoBac (Bti) range from Sumitomo Chemical. However, for pest managers and organisations with limited resources, the use of a product such as VectoPrime (also from Sumitomo Chemical), which combines both actives into a single product, provides pest managers with a product with increased performance and flexibility in application.
Not only is VectoPrime really the only type of product for use when multiple larval stages are present, it can be applied at any time, eliminating the need for monitoring, and providing complete flexibility in application timing. Even pre-flood applications are possible in certain environments. As Bti does not require the larvae to moult, reduced mosquito larvae numbers can be observed within 24 hours.
Larvicide applications are an essential tool for mosquito management programs and Sumitomo offers a range of products for different situations (residential, commercial and council estuarine applications) and for different application methods (spray equipment and granule spreaders). As well as VectoPrime, Sumitomo produces a range of VectoBac products in different formats (liquids and granules), as well as Sumilarv Granular (pyriproxyfen) in pre-dosed sachets, which is ideal for treating small water bodies.
