Which term describes an herbicide used to destroy brush and trees?

The term that describes an herbicide specifically designed to destroy brush and trees is "silvicide". This designation indicates that silvicides are formulated to target woody plants, including various types of brush and trees, effectively controlling unwanted growth in forest management, land clearing, and other scenarios where such vegetation can be problematic.

Herbicides, while they broadly refer to any chemical used to kill plants, do not exclusively pertain to woody vegetation; they encompass a wider range of plant control substances. Insecticides are designed to control insect populations, and fungicides target fungal pests. Thus, the specific term "silvicide" reflects the targeted action of the herbicide on brush and trees, making it the correct choice in this context.