What do 'neonicotinoids' primarily target?

Neonicotinoids primarily target the nervous system of insects, which is why the selection of this answer is appropriate. These pesticides are chemically similar to nicotine and act on specific receptors in the insect brain, leading to neurotoxicity. This disrupts normal nervous system functioning, resulting in paralysis and death of the target pests.

Neonicotinoids are particularly effective against piercing-sucking insects like aphids and whiteflies. Their targeting of insect nervous systems explains their widespread use in agricultural practices to manage harmful insect populations effectively.

The other options, such as fungi, weeds, and bacteria, do not represent the primary targets of neonicotinoids, as they are not designed to affect these organisms. Fungal pathogens typically require fungicides for control, while herbicides are used to target weeds. Bacterial diseases would necessitate the use of bactericides. Thus, the specificity of neonicotinoids for insects sets them apart as a unique class of pesticides.