This chapter focuses on the method of controlling juvenile mosquitoes while in life stages (larvae & pupae) which only occur in water. To safely alter our aquatic environments, even temporarily, for the purpose of controlling mosquitoes, requires a good working knowledge of both the target species and larvicides, which include commercial pesticides and natural predators. Products and techniques currently used in Florida are discussed in detail, and the benefits and risks of each are considered. Commercial pesticide information includes summaries and information provided by manufacturers. Minor differences between various formulations of the same or similar active ingredients are detailed so ...view middle of the document...
Most mosquito species spend much of their life cycle in the larval
stage when they are highly susceptible to both predation (see Chapter 7) and control efforts. They often are concentrated within defined water boundaries, immobile with little ability to disperse, and accessible. Adult mosquitoes, in contrast, fly in search of mates, blood meals, or water sources for egg laying and are often inaccessible, not concentrated, and widely distributed. Therefore, effective larviciding can reduce the number of adult mosquitoes available to disperse, potentially spread disease, create a nuisance, and lay eggs which leads to more mosquitoes.
The effective control of larvae and/or pupae is a basic principle of Integrated Pest Management (IPM). Effective IPM involves understanding the local mosquito ecology and patterns of arbovirus transmission and then selecting the appropriate mosquito control tools. The most common methods of IPM include Environmental Management, or Source Reduction (Chapter 4), Larviciding, and Adulticiding (Chapter 6). Other mosquito control principles include Biocontrol (Chapter 7), as well as additional methods not discussed here such as herbiciding and hand removal of aquatic plants. These methods may be used to control immature mosquitoes indirectly, usually when there is an obligatory association between the larvae/pupae and specific host plants. In Florida, Mansonia and Coquellittidia mosquitoes are associated with aquatic plants.
Common examples of highly concentrated broods include immature Aedes taeniorhynchus and Ae. sollicitans in saltmarsh pools, Psorophora columbiae in flooded pastures, and species such as Culex nigripalpus in wastewater treatment sites. In these situations, most Florida mosquito control programs larvicide as a management practice because it both minimizes the area in which control procedures must be applied and reduces the need for adult control. At these times, larviciding has a high impact on local population numbers with minimal application efforts. At other times, larviciding may be less rewarding because small numbers of larvae and pupae are widely and unevenly distributed. Examples include Culiseta melanura in bay tree swamps, Mansonia species and Cq. perturbans in large freshwater marshes with patchy host plant distribution, and Anopheles quadrimaculatus in large, overgrown grassy retention ponds.
Planning a LSM strategy is crucial to a highly effective control program. The first step begins with adult and larval surveillance. Once surveys have been conducted, it is then important to map out and prioritize potential larval habitats. Treatment thresholds, often based on the number of larvae encountered at a site, should be established to justify larviciding, and action plans appropriate for the sites should be developed.
It is important to select the appropriate control agent and formulation based on performance and other factors. It is critical to have a thorough knowledge of the...