How does Metalaxyl compare to Mancozeb?

Metalaxyl and Mancozeb are both effective fungicides but differ in their mode of action, target pathogens, and application strategies. Here’s a comparison:

1. Mode of Action

• Metalaxyl: A systemic fungicide from the acylalanine group, Metalaxyl is absorbed by the plant and translocated to new growth, providing both protective and curative action. It targets specific pathogens by inhibiting RNA synthesis in fungal cells.
• Mancozeb: A contact fungicide from the dithiocarbamate group, Mancozeb works by preventing fungal spores from germinating on the plant surface. It does not penetrate plant tissue, so its effect is primarily preventative.

2. Target Pathogens

• Metalaxyl: Primarily targets oomycetes (water molds), including pathogens like Phytophthora (potato late blight) and downy mildew in various crops.
• Mancozeb: Broad-spectrum, effective against many types of fungal diseases, including leaf spots, blights, rusts, and downy mildews. It’s often used as a multi-target fungicide.

3. Application and Persistence

• Metalaxyl: As a systemic fungicide, it’s typically applied as a foliar spray or a seed treatment. It moves within the plant, protecting both treated and new growth. Metalaxyl is highly effective in low doses and has longer persistence.
• Mancozeb: Applied as a foliar spray, but only protects the treated surface of the plant. It requires more frequent application, especially after rain, due to its contact-only action.

4. Resistance Management

• Metalaxyl: There is a risk of resistance development among certain pathogens with repeated use. It’s advised to rotate or mix Metalaxyl with other fungicides like Mancozeb to mitigate resistance risk.
• Mancozeb: Because it affects multiple sites within fungal cells, Mancozeb has a lower risk of resistance development. It’s often used as a partner fungicide in tank mixes for resistance management.

5. Combination and Use in Integrated Programs

• Tank Mixes: Metalaxyl is often mixed with Mancozeb to provide both systemic protection and broad-spectrum contact action, especially in crops like potatoes, grapes, and vegetables.
• Complementary Uses: In integrated pest management, Metalaxyl provides systemic control for oomycete pathogens, while Mancozeb serves as a protective barrier against a broader range of fungi, providing an effective and complementary approach.

Summary

Metalaxyl and Mancozeb, when used together, can offer effective, broad-spectrum control with both systemic and contact action, enhancing the protection and resilience of crops against fungal diseases.