Question

A pathogen often develops resistant against ........ ?

• A. Systemic fungicides
• B. Dusts
• C. Fumigants
• D. Pastes

Hint:

To delay the development of fungicide resistance in the field:
- Avoid continuous use of a single systemic fungicide.
- Rotate or mix systemic fungicides with broad-spectrum, multi-site contact fungicides (like copper oxychloride or mancozeb), which are much harder for pathogens to bypass through single mutations.

Answer 1

The Correct Option is A

Step 1: Understanding the Concept:
Pesticide resistance is the inherited ability of a pest or pathogen population to survive exposure to a chemical agent that was previously effective at controlling it.
The speed at which resistance develops depends on the chemical's mode of action.

Step 3: Detailed Explanation:
Let us analyze how pathogens interact with different crop protection formulations:
- Systemic Fungicides (A): These chemicals are absorbed by plant tissues and transported throughout the plant's vascular system.
Most systemic fungicides are single-site inhibitors, meaning they target a single specific enzyme or biochemical pathway in the pathogen (e.g., inhibiting tubulin synthesis or sterol biosynthesis).
Because they target a single site, a single gene mutation in the pathogen can alter the target enzyme, making the population highly resistant to the fungicide.
This specific mode of action allows pathogen populations to develop resistance rapidly under continuous use.
- Let us analyze the other options:
- Dusts, Fumigants, and Pastes describe physical formulations or methods of application rather than distinct biochemical modes of action.
Fumigants, for example, typically use broad, multi-site non-specific toxicants that disrupt multiple physiological systems simultaneously, making it difficult for pathogens to develop genetic resistance.
Therefore, pathogens develop resistance most easily against systemic fungicides.

Step 4: Final Answer:
Pathogens develop resistance most frequently against systemic fungicides, matching Option (A).