Our mosquito control contractor starts monitoring weather, snowpack and river levels in early-March each spring. These meteorological data help the control staff to determine which larval development sites may be active with mosquito larvae. There are over 450 known larval development sites in the TNRD and they are classified as "snowmelt" (early-spring ponds and marshes in the grasslands and Logan Lake area that become active very early in the spring), of "floodwater" (sites along the North and South Thompson Rivers that active with rising water in the spring). Mosquito control staff search standing water for mosquito larvae before every larviciding treatment and never treat unless larvae are present. This is called mosquito larval monitoring and it is done with a 300 ml “dipper”. All larvae are counted and the “dip counts” are recorded as per Ministry of Environment regulations.

Surveillance staff maintain 8 adult mosquito trapping stations within the TNRD. These stations are visited weekly to collect any mosquitoes captured. The samples are taken to a lab where they are examined under a microscope to determine their species. There are approximately 30 species of mosquitoes in the TNRD. Some of these are persistent and ferocious biters of humans, some have the potential to transmit disease and others never bite humans at all. The species and their abundances are recorded and this information is used by mosquito control staff to determine areas of high priority. It is also useful as a means of helping staff find mosquito larvae, since different species develop in different types of larval development habitats. For example, some mosquito species like floodwaters, others develop in permanent or semi-permanent marshes, and still others prefer artificial containers.