Larviciding is the most cost-effective method of mosquito control. The SCHD Mosquito Control program consists of cataloging and monitoring mosquito larval habitats, identifying the presence and type of mosquito larvae, and eliminating mosquito larvae by application of insecticides (i.e. larvicides) approved by the Environmental Protection Agency (EPA). Eliminating mosquitoes in larval stages before maturation to the adult stage reduces the need to spray adulticides and thereby the cost of abatement operations. This approach represents a primary form of disease prevention as practiced in public health through targeting the source of mosquito problem.
Larval sampling is a critical part of the daily Mosquito Control operations. Trained personnel survey areas where water is present, a necessity for mosquito proliferation. This process allows Mosquito Control staff to estimate the size of larval mosquito preparing to emerge within that location. Staff also monitors environmental conditions, such as temperature, which assists in predicting developmental rates of larvae. This provides the combined data to estimate the time and place of needing to schedule adulticiding. Larviciding activities are performed daily at all assigned municipality sites during mosquito season (April - November).
Adulticiding is the form of control used against adult mosquitoes. The most common form of adulticiding, and the form used by Shelby County, utilizes Ultra Low Volume (ULV) sprayers mounted on trucks. Adulticiding is performed according to Centers for Disease Control and Prevention (CDC) protocol and based upon surveillance data. All ULV spray units have been calibrated according to requirements given on each Insecticide label and the droplet cloud (i.e. spray mist) analyzed to fulfill legal requirements and ensure maximum efficacy. All adulticides used by SCHD Mosquito Control are approved by EPA for use in residential and rural areas. Adulticiding is performed when the following events are confirmed:
- Results of testing mosquito pools (approximately 50 female mosquitoes / pool) indicating the presence West Nile Virus or St. Louis Encephalitis
- Epidemiological identification of West Nile Virus or St. Louis Encephalitis human cases
- High populations of adult mosquitoes
Mosquito related data is required to justify adulticiding under the new National Pollutant Discharge and Elimination System (NPDES). Adulticiding cannot be scheduled solely upon requests from citizens.