What is defined as a toxicant?

A toxicant is specifically defined as a poisonous material, which aligns directly with the chosen answer. Toxicants can cause harm to living organisms through various mechanisms, often when they are ingested, inhaled, or absorbed. Understanding this definition is crucial for anyone involved in pesticide application, as it helps in recognizing the potential hazards associated with various chemicals used in agricultural and aquatic environments.

In contrast, the other options describe substances that do not fit the definition of a toxicant. For example, a chemical that enhances pest resistance may contribute positively to pest management strategies but does not inherently possess toxic properties to living organisms. Similarly, a substance that increases agricultural productivity may be beneficial in promoting plant growth without being poisonous. Lastly, a natural substance used in organic farming often emphasizes sustainability and safety rather than toxicity, as these substances are typically chosen to minimize harmful impacts on the environment and health.