Chemical Class and Multi-Site Mode of Action
Captan belongs to the phthalimide chemical family (FRAC Group M04), functioning as a non-systemic multi-site contact protectant.
It reacts with fungal cellular thiol groups (-SH), inactivating essential metabolic enzymes, halting fungal respiration, and preventing spore germination.
- Multi-Site Activity: Attacks multiple cellular biochemical pathways, preventing fungi from developing target-site resistance
- Protective Barrier: Forms an external chemical barrier on leaf, blossom, and fruit surfaces that kills germinating spores on contact
- Surface Redistribution: Excellent surface adhesion and rain resistance, protecting developing fruit finishes
Target Crops and Fungal Pathogens
Captan is widely registered across temperate fruit orchards, commercial vegetables, and field crops.
It is a global benchmark for managing apple scab (Venturia inaequalis) and damping-off in nursery seedling beds.
- Apple: Apple scab and brown rot control from silver tip through petal fall and cover sprays
- Grapes & Berries: Downy mildew, black rot, and fruit rot management
- Vegetables (Tomato, Potato, Chilli): Early blight, anthracnose fruit rot, and Alternaria leaf spot
- Seed Treatment: Protects sprouting seeds of pulses, maize, and cotton from damping-off and seed-borne rots
Application Guidelines and Tank-Mix Precautions
Because Captan is a preventive contact protectant, apply before disease outbreaks or during damp weather that fosters fungal sporulation.
Never tank-mix Captan with alkaline materials, sulfur, or petroleum-based horticultural oils, as severe crop foliage injury can occur.
- Oil Incompatibility: Never apply within 10 to 14 days of horticultural spray oil applications to avoid leaf phytotoxicity
- Seed Dressing Rate: Apply 2 to 3 grams per kilogram of seed for dry seed dressing prior to sowing
- Foliar Volume: Use 200 liters of water per acre (or 400 to 500 liters in orchards) for thorough canopy coverage
Official source
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Central Insecticides Board & Registration Committee ↗Related on KisanPe
Common questions
What is the mode of action of Captan fungicide?
Captan is a multi-site contact protectant that reacts with fungal thiol enzymes, blocking cellular respiration and preventing spore germination.
Can Captan be mixed with horticultural spray oil?
No, Captan should never be mixed with or applied within 10 to 14 days of spray oils, as the combination causes severe leaf burning.
Why is fungal resistance rare with Captan?
Because Captan attacks multiple biochemical cellular sites simultaneously, fungi cannot develop resistance through simple single-gene mutations.
General guidance, not personal advice. For your farm, ask your local Krishi Vigyan Kendra or agriculture officer.
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