Using Sulphur powder to control fungal diseases on plants
Pear Rust on Leaves
1. Fungitoxic Activity (Direct Toxicity to Fungi)
Sulphur interferes with the metabolism of fungal cells. When sulphur is applied to leaves, it oxidizes slowly (especially in the presence of moisture and warmth) to form sulphur dioxide (SO₂) and hydrogen sulphide (H₂S)—both of which are toxic to fungal spores. These compounds:
- Inhibit fungal respiration by disrupting enzymes in fungal cells.
- Damage cell walls and structures, preventing the fungus from growing and reproducing.
2. Creates an Unfavorable Surface Environment
Sulphur changes the pH on the surface of the leaf, making it more acidic. Many fungal spores struggle to germinate in lower pH conditions, reducing their ability to infect the plant.
3. Prevention of Spore Germination
Even before a fungus penetrates the leaf, sulphur can prevent spores from germinating on the surface. It disrupts the early growth stages of pathogens like powdery mildew, one of the primary targets of sulphur.
4. Repellent and Protective Barrier
The powder acts as a physical barrier that repels some pests and pathogens, reducing the chance of infection. It also reflects some sunlight, potentially reducing humidity on leaf surfaces, which is another deterrent to fungal growth.
Important Notes:
- Best against powdery mildew and some rusts—less effective against downy mildew or systemic fungal infections.
- Environmental conditions matter: sulphur is most effective in warm, dry conditions. In high humidity or rain, its effectiveness decreases.