Which of the following fungi is Captan effective against?

• A. Phytophthora
• B. Rhizoctonia
• C. Pythium
• D. Verticillium

Answer: (B)

Captan is a broad-spectrum fungicide that is primarily effective against certain fungal pathogens, particularly those that affect seeds and seedlings. It acts as a protectant, preventing the growth and spread of fungi that can cause diseases in plants.

Rhizoctonia is a soil-borne fungus that is responsible for several diseases in a variety of crops, including damping-off, root rot, and stem rot. Captan's effectiveness against Rhizoctonia comes from its ability to inhibit spore germination and mycelial growth of this particular fungus, making it particularly useful in protecting seeds and young plants during critical growth stages.

Although Captan has some ability to control other pathogens as well, such as certain strains of Pythium, it is not universally effective against all types of fungi. Therefore, recognizing its targeted action against Rhizoctonia helps explain why this choice is correct. Understanding the specificity of fungicides and the particular diseases they combat is essential for effective disease management in agriculture.