Which statement about mosquito larvicides is true regarding their application?

The statement about mosquito larvicides that is true regarding their application is that some larvicides are only effective at specific stages. This is an important consideration in mosquito control because different larvicides target different developmental stages of the mosquito lifecycle. For example, some larvicides may be effective only against larvae, while others might work on pupae or eggs. Understanding the specific life stages that a particular larvicide targets is crucial for ensuring effective treatment and controlling mosquito populations.

This knowledge helps in selecting the appropriate larvicide for specific situations, especially since the effectiveness can vary widely depending on the development stage of mosquitoes present in the treated area. Using a larvicide that is effective at the right stage can improve control outcomes and reduce potential resistance in mosquito populations.

Addressing the other options, not all larvicides can be evaluated equally due to their differing modes of action and life stage targeting; extensive pre-site evaluations may not always be necessary depending on the type of treatment; and larvicidal activities are indeed influenced by environmental factors such as temperature, pH, and the presence of organic matter, which can affect the efficacy of various larvicides.