What type of organisms are most affected by BTI during treatments?

The correct choice is focused on the fact that BTI, or Bacillus thuringiensis israelensis, specifically targets certain types of organisms. BTI is a biological pesticide that produces toxins harmful to specific insect larvae, especially mosquitoes and black flies. When BTI is used in water bodies, it effectively infects and kills the larvae of these insects while having minimal impact on other organisms, such as fish, birds, and mammals, due to the specificity of the toxin's action.

In contrast to other groups listed, insects, particularly mosquito larvae, are uniquely vulnerable to BTI because they possess the necessary receptors for the toxins produced by this bacterium. This makes BTI a targeted and environmentally friendly choice for reducing mosquito populations without disrupting other wildlife, which is crucial for maintaining ecosystem balance. Thus, the effectiveness of BTI against mosquito larvae is clearly aligned with its intended purpose as a biological control agent.