Metalaxyl

The appearance of pure product is white crystals. m.p. 71-72℃ , vapor pressure 2.933×10-4Pa(20℃ ), relative density 1.21(20℃ ). Soluble in many organic solvents, solubility in methanol is 65%, solubility in water is 0.71% (20℃ ). It is more stable in acidic and neutral media. The original powder is yellow to brown powder, fl ash point 155℃ (closed-dish type). Non-fl ammable, non-explosive, non_x005f corrosive.

A systemic fungicide, used as a fungicide for tobacco, rubber trees, grapes, hops, melons, vegetables, etc.

Metalaxyl is a systemic fungicide widely used in agriculture to control a broad range of fungal diseases, particularly those caused by Phytophthora, Pythium, and other oomycetes. It is commonly applied to crops like potatoes, tomatoes, grapes, and various vegetables to prevent root rot, blight, and downy mildew. Metalaxyl works by inhibiting the growth of fungal pathogens and preventing their spread within the plant.

Key Features

1. Chemical Class: Acylalanine

2. Mode of Action: Metalaxyl is a systemic fungicide that is absorbed by plant roots and leaves. It works by inhibiting the synthesis of ribonucleic acid (RNA) in the fungal cells, which disrupts their ability to reproduce and spread.

3. Formulations: Available in various formulations such as suspension concentrates (SC), wettable powders (WP), and granular formulations.

4. Target Pathogens: Effective against oomycete fungi, particularly Phytophthora, Pythium, and Peronospora species, which cause diseases like root rot, late blight, and downy mildew.

Applications

Crops

• Potatoes: Metalaxyl is widely used to control late blight (Phytophthora infestans), a disease that can devastate potato crops.

• Tomatoes: It helps prevent late blight and other fungal diseases that can affect tomato plants.

• Grapes: Applied to control downy mildew (Plasmopara viticola), which can significantly reduce grape yield and quality.

• Vegetables: Metalaxyl is also used to protect a variety of vegetables, including peppers, cucumbers, and lettuce, from oomycete pathogens.

Target Diseases

• Late Blight: Caused by Phytophthora infestans, this disease affects leaves, stems, and tubers, leading to rapid plant death if not controlled.

• Downy Mildew: Caused by Plasmopara and Peronospora species, this disease affects the leaves and can lead to defoliation and reduced photosynthesis.

• Root Rot: Caused by Pythium and Phytophthora species, this disease affects the roots, leading to stunted growth, wilting, and plant death.

Mode of Action

Metalaxyl is absorbed by the plant and translocated through the vascular system, providing systemic protection. It works by inhibiting the biosynthesis of RNA in fungal cells, preventing them from reproducing and growing. This action stops the fungus from spreading and causing further damage to the plant.

Advantages

1. Systemic Protection: Metalaxyl offers long-lasting protection by being absorbed and distributed throughout the plant, providing both preventive and curative action.

2. Broad Spectrum: It is effective against a wide range of oomycete pathogens, making it versatile for use on multiple crops.

3. Prevention and Cure: Metalaxyl can be applied both preventively, before symptoms appear, and curatively, after disease onset, to stop the spread of infection.

4. Low Toxicity to Non-Target Organisms: When used according to label instructions, metalaxyl has relatively low toxicity to beneficial insects, aquatic organisms, and wildlife.

Usage Guidelines

1. Application Timing:

   • Preventive Application: Apply before the onset of disease symptoms, especially during periods of high humidity or rainfall.

   • Post-Symptom Application: Metalaxyl can also be applied after symptoms appear, but it is most effective when used preventively.

   
   

2. Dosage: The recommended dosage varies depending on the crop and disease pressure. It typically ranges from 0.5 to 2 kg/ha.

3. Spray Coverage: Ensure thorough coverage of the plant, especially the leaves and stems, for maximum effectiveness.

4. Reapplication Interval: Reapply every 7–14 days, depending on the severity of the disease and environmental conditions.

Safety and Environmental Considerations

Handling and Storage

• Protective Measures: Wear appropriate personal protective equipment (PPE) such as gloves, goggles, and protective clothing when handling metalaxyl.

• Storage: Store in a cool, dry place, away from food, feed, and water sources. Keep containers tightly sealed to avoid contamination.

Environmental Impact

• Aquatic Toxicity: Metalaxyl has moderate toxicity to aquatic organisms, so care should be taken to avoid runoff into water bodies.

• Soil Persistence: It has low persistence in soil, which reduces the risk of long-term environmental contamination.

• Non-Target Organisms: Metalaxyl is generally safe for beneficial insects and pollinators when used as directed, but care should be taken to avoid exposure to bees during application.

Human Health Risks

• Toxicity: Metalaxyl is of low toxicity to humans when used according to label instructions. However, it is important to avoid inhalation or skin contact.

• First Aid:

  • Skin Contact: Wash with soap and water immediately.

  • Eye Contact: Rinse thoroughly with water for at least 15 minutes.

  • Inhalation: Move to fresh air and seek medical attention if symptoms persist.

  
  

Resistance Management

To reduce the risk of resistance, it is recommended to rotate metalaxyl with fungicides from different chemical classes. Overuse of any single fungicide can lead to resistance, reducing its effectiveness over time.

Limitations

1. Resistance Risk: Like all fungicides, metalaxyl can contribute to resistance if overused. It is important to follow a resistance management strategy to avoid this.

2. Rainfastness: Metalaxyl is typically rainfast within 1–2 hours of application, but heavy rainfall shortly after application may reduce its effectiveness.

3. Limited Efficacy Against Non-Oomycete Fungi: Metalaxyl is most effective against oomycetes but may not control other types of fungal infections.

Conclusion

Metalaxyl is a highly effective systemic fungicide that provides long-lasting protection against a wide range of oomycete pathogens, including late blight and downy mildew. Its ability to be absorbed and translocated throughout the plant makes it a versatile tool in integrated disease management programs. By following recommended usage guidelines and incorporating resistance management practices, metalaxyl can help protect crops and improve yields.