Selectively used herbicides are specifically designed to do what?

Selectively used herbicides are formulated to target and affect only certain species of undesirable plants while leaving other desirable species unharmed. This method is crucial in aquatic pest control as it allows for the management of invasive or harmful plant species without disrupting the overall ecosystem balance. By focusing on specific plants, these herbicides can effectively reduce competition for resources without completely eliminating beneficial plant life, which can be vital for the health of aquatic environments.

The other options highlight approaches that do not align with the purpose of selective herbicides. Controlling all species of plants or eliminating all aquatic vegetation could lead to ecological imbalances and damage the habitat. Similarly, promoting growth in all plants would not address the presence of unwanted species, which is precisely what selective herbicides aim to manage.