Under which condition should a vehicle be placarded for pesticide transport?

A vehicle should be placarded for pesticide transport when it contains containers larger than 119 gallons. This is a safety regulation that ensures appropriate labeling and identification of the vehicle's contents, which is crucial for emergency responders in the event of an accident or spill. Larger containers represent a significant quantity of hazardous materials, and their placarding helps to communicate the potential risks associated with transporting these substances.

Regarding the other options, while specifics such as DOT permits and quantity thresholds are important in other regulatory contexts, they do not specifically trigger the requirement for placarding like the size of the container does. Liquid pesticides can certainly be hazardous, but the singular focus on size (over gallons) is what dictates placarding. Therefore, ensuring that the transport vehicle is compliant with regulations related to container size plays a critical role in safety and legal adherence in pesticide transportation.