Surface oils are most effective against which life stage of mosquitoes?

Surface oils are most effective against the larval stage of mosquitoes because they disrupt the ability of larvae to breathe through their siphon, a structure they use to obtain oxygen from the water surface. When surface oils are applied to water, they form a thin film that covers the surface, preventing the exchange of gases. This makes it difficult for mosquito larvae to access the oxygen they need to survive, ultimately leading to their demise.

While other life stages of mosquitoes may be impacted by certain pesticides or control methods, surface oils specifically target the larvae. Eggs are generally protected from physical agents like oils by their outer shell, while adult mosquitoes are primarily affected by other control methods such as sprays or traps that target their flying behavior. Therefore, the primary effectiveness of surface oils lies in their action against larvae in aquatic habitats.