What types of chemicals are available for disease control?

The correct answer highlights the three primary categories of chemicals used explicitly for disease control in agricultural and horticultural practices. Protective chemicals refer to those that act as a barrier to prevent infections, often applied preventively before the disease occurs. Systemic chemicals, on the other hand, are absorbed by the plant and provide internal protection against diseases from the inside out. Soil fumigants are utilized in treating the soil to eliminate pathogens and pests before planting, thereby reducing the risk of disease.

In contrast, the other options do not focus specifically on disease control. The second response includes categories of chemicals targeted towards various pests and weeds rather than disease-causing organisms. The third option lists chemicals that target specific pests, such as fungi, mites, and bacteria, but it does not encompass the broader categories and types used for effective disease management in agricultural systems. Lastly, the fourth choice lists substances that support plant growth and health rather than directly controlling diseases, making it unrelated to disease control strategies.