Active Chemical Composition & Mode of Action
Ridomil Gold combines two synergistic fungicides representing different FRAC groups. Metalaxyl-M (the biologically active R-enantiomer of metalaxyl) is a systemic phenylamide fungicide (FRAC Group 4) that inhibits RNA polymerase-I in fungal nucleic acid synthesis.
Mancozeb is a broad-spectrum contact dithiocarbamate fungicide (FRAC Group M03) that disrupts multiple metabolic enzymes, providing a protective surface barrier and preventing fungal resistance development.
- Active Ingredients: Metalaxyl-M 4% w/w + Mancozeb 64% w/w WP (Wettable Powder)
- FRAC Classification: Group 4 (PA-fungicide) + Group M03 (Multi-site contact activity)
- Systemic Translocation: Rapidly absorbed by roots and foliage; translocated upward via xylem vessels
- Formulation Quality: Micro-fine wettable powder providing uniform leaf canopy adhesion
Approved Target Crops & Key Plant Pathogens
Ridomil Gold is registered under the CIBRC primarily for controlling diseases caused by Peronosporales (Oomycetes). It provides exceptional protection during cool, cloudy, and humid weather when sporulation rates peak.
Approved labeled crops include potatoes, tomatoes, grapes, black pepper, and nursery seedlings prone to Pythium and Phytophthora soil-borne damping-off.
- Late Blight: Highly effective against Phytophthora infestans on potato foliage and tomato crops
- Downy Mildew: Protects grapevines (Plasmopara viticola) and cucurbits against foliar mildew lesions
- Damping-Off & Foot Rot: Controls Pythium damping-off in vegetable nurseries and Phytophthora foot rot in citrus
- Preventative Timing: Apply before disease symptoms become widespread across the field
Foliar Spraying & Resistance Stewardship
Metalaxyl-M provides curative activity if applied within 24 to 48 hours of fungal infection, while Mancozeb prevents new spore germination on leaf surfaces. Thoroughly coat both upper and lower leaf surfaces.
To prevent resistant Oomycete strains from emerging, limit applications to a maximum of two to three sprays per crop season, rotating with alternative non-phenylamide fungicides (such as copper oxychloride or dimethomorph).
- Application Method: Foliar spray using hollow-cone nozzles for dense mist coverage
- Rainfastness: Systemic fraction is rainfast within 1 to 2 hours after spray droplets dry
- Waiting Period: Comply with the statutory pre-harvest interval (PHI) specified on the container label
- Personal Safety: Wear protective gloves, eye protection, and apron while measuring wettable powder
Official source
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Central Insecticides Board & Registration Committee (CIBRC) ↗Related on KisanPe
Common questions
What is the technical chemical composition of Ridomil Gold?
It contains Metalaxyl-M 4% and Mancozeb 64% WP, providing both systemic RNA-polymerase inhibition and multi-site contact surface protection.
Why is Ridomil Gold preferred over older Metalaxyl formulations?
It uses Metalaxyl-M (the refined active R-enantiomer), providing superior systemic efficacy at half the active dose compared to racemic metalaxyl.
Can Ridomil Gold cure plants already severely infected with late blight?
It offers early curative action within 24 to 48 hours of initial infection, but cannot revive necrotic, blackened leaf tissues once severe blight has destroyed the foliage.
General guidance, not personal advice. For your farm, ask your local Krishi Vigyan Kendra or agriculture officer.
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