Which of the following methods is NOT typically used to control aquatic weeds?

Freezing is not typically utilized as a method for controlling aquatic weeds. This is primarily due to the fact that most aquatic plants are adapted to withstand varying water temperatures, and freezing conditions would need to be sustained over a prolonged period to have any effective impact on the growth of these plants.

In contrast, methods like biological control, where natural predators or diseases target the weeds, and drawdown, which involves lowering water levels to expose and dry out the weeds, are commonly employed because they actively manage and reduce weed populations effectively. Dyes are also used in aquatic settings to inhibit light penetration, thereby limiting photosynthesis and growth of weeds. Each of these methods targets the biology or environment of aquatic plants in a way that freezing simply cannot achieve.