What term describes a chemical that causes the leaves of a plant to drop prematurely?

The term that describes a chemical that causes the leaves of a plant to drop prematurely is "defoliant." Defoliants are specifically designed to induce leaf drop, which can be a useful process in various agricultural practices, including harvesting and weed management. By promoting the shedding of leaves, defoliants can help increase air circulation and facilitate the ripening of crops.

In contrast, a desiccant is a substance that promotes drying, primarily used to remove moisture from the atmosphere, which is not directly related to leaf drop. A disinfectant is a chemical used to destroy or inhibit the growth of harmful microorganisms on surfaces, and it does not pertain to plant physiology or leaf drop. The term "dilute" refers to decreasing the concentration of a solution, which is also unrelated to the process of defoliation. Thus, defoliant is the most accurate term for a chemical that prompts leaves to fall prematurely.