Which group of insects would insecticides be most effective against?

Insecticides are specifically designed to target insects, and they function by disrupting the biological processes that are unique to these pests. Therefore, mosquitoes that spread malaria, which are indeed insects, are the group that insecticides are most suitable for. These chemicals are formulated to target the nervous systems and reproductive capabilities of insects, making them effective in controlling insect populations that carry diseases like malaria.

In contrast, bacteria and fungi represent different biological classes that do not respond to insecticides. Bacteria, such as Salmonella, require antibiotics or disinfectants for control. Similarly, fungi that contribute to molds and mildew need fungicides for management. Weeds, although they can be problematic in agriculture, are not insects; thus, herbicides—specifically designed for plants—would be used to manage those types of growth.

This contextual understanding underscores why insecticides are primarily effective against insect pests, like malaria-carrying mosquitoes, as opposed to the other listed options which involve different types of organisms.