Broad-spectrum pesticides are formulated to affect a wide range of pests, which means they can effectively target various organisms that may cause harm to crops or the environment. This category includes not just insects, but also weeds, fungi, and other plant pathogens. The versatility of broad-spectrum pesticides allows them to be used in diverse agricultural situations where multiple types of pests may be present, providing a comprehensive approach to pest management.
The choice that implies targeting only insects, only plant diseases, or only weeds represents a more limited scope and does not reflect the capability of broad-spectrum pesticides to manage a variety of pest issues across different categories. Thus, the correct answer highlights the broader application and efficacy of these substances against multiple pest types.