Question

Sulfur-based fungicides are used against which of the following diseases?

• A. Red rot
• B. Stem rot
• C. Powdery mildew
• D. Downy mildew

Hint:

Associate Sulfur fungicides directly with Powdery Mildew management.
Conversely, remember that Copper fungicides (like Bordeaux mixture) are typically used for Downy Mildew.

Answer 1

The Correct Option is C

Step 1: Understanding the Concept:
Fungicides are chemical compounds used to manage and prevent fungal infections in crops.
Different classes of fungicides (such as sulfur-based, copper-based, or systemic fungicides) target specific fungal structures and groups of plant pathogens.

Step 2: Detailed Explanation:
Elemental and sulfur-based fungicides (such as wettable sulfur, sulfur dust, or lime-sulfur) are among the oldest effective pesticides.
They work by disrupting the respiratory chain of fungi, specifically interfering with the transfer of electrons in the mitochondrial system.
- Powdery Mildew: This disease is caused by obligate biotrophic fungi belonging to the order Erysiphales.
The mycelium grows superficially on the host leaves, making the fungal structures highly vulnerable to direct contact with sulfur-based fungicides.
Sulfur exerts direct contact toxicity and has a vapor action that effectively controls powdery mildew.
- Downy Mildew: Caused by oomycetes, which are biologically distinct from true fungi. They are usually controlled by copper-based or specific systemic fungicides (like metalaxyl), and sulfur is ineffective against them.
- Red Rot and Stem Rot: These are deep-seated tissue or stem infections that require specific systemic or broad-spectrum fungicides rather than elemental sulfur.
Therefore, sulfur-based fungicides are specifically used to control powdery mildew.

Step 3: Final Answer:
Sulfur-based fungicides are used against Powdery mildew.