Environmental conditions such as climatic conditions (e.g., temperature and humidity), mosquito fitness (e.g., age, size, and feeding status), insecticide exposure time (e.g., fleeting contact vs extended exposure), and insecticide dose (depending on, e.g., time since application, washes, and insecticide half-life), which all vary over space and time, impact phenotypic resistance. To measure technical resistance, a particular phenotype (depending on the test used) is measured under standardized conditions. Variation is introduced by the researcher performing the test (e.g., variation in mosquito handling, test preparation, and mortality scoring). Phenotypic resistance translates indirectly to disease transmission: insecticide-resistance mechanisms and the insecticide itself impact the mosquitoes’ vectorial capacity (i.e., the ability of mosquito populations to transmit a specific pathogen from human to human) through host choice (e.g., frequency of human vs non-human biting), biting rate (i.e., frequency of taking a human blood meal), reproductive fitness (i.e., the ability of a mosquito to pass on her genes to subsequent generations, which is importantly impacted by survival, fertility, and ability to mate), and vector competence (i.e., the capacity of a mosquito to acquire, maintain, and transmit a parasite). In addition, phenotypic resistance indirectly translates to disease transmission through factors impacting the field efficacy of vector control tools because of aforementioned environmental conditions (i.e., practical resistance). The variation in use and deployment of the tool impacts the efficacy of the vector control tool itself, as well as vectorial capacity. Overall, these indirect effects could lead to poor correlation between standardized phenotypic tests and impact on disease transmission.