Chemical Class and Cellulose Synthase Inhibition
Dimethomorph 50% WP belongs to the cinnamic acid derivative / Carboxylic Acid Amide (CAA) class of fungicides. It selectively targets Oomycete pseudofungi by inhibiting cellulose synthase enzymes.
Because Oomycete cell walls are constructed primarily of cellulose rather than chitin, Dimethomorph prevents cell wall deposition, causing lysis of fungal germ tubes, haustoria, and sporangia within host plant tissues.
- Active ingredient: Dimethomorph 50 percent w/w WP (Wettable Powder)
- Fungicide group: FRAC Group 40 (Carboxylic Acid Amides - CAA / Cellulose synthase inhibitors)
- Systemic mobility: Strong translaminar movement across leaf blades and localized xylem acropetal transport
- Activity spectrum: Selective activity against Oomycetes (*Plasmopara*, *Phytophthora*, *Pseudoperonospora*)
CIBRC Approved Target Diseases and Crops
The Central Insecticides Board registers Dimethomorph 50% WP for destructive water-mold and downy mildew pathogens across high-value horticulture and vegetable crops.
Its translaminar action protects both upper and lower leaf surfaces, suppressing latent mycelial colonization and preventing the production of viable secondary sporangia.
- Grapes: Downy mildew (*Plasmopara viticola*) on leaves, tendrils, and floral bunches
- Potato: Late blight (*Phytophthora infestans*) on foliar foliage and stems
- Tomato: Late blight and buckeye fruit rot
- Cucurbits: Downy mildew (*Pseudoperonospora cubensis*) across melons and gourds
Application Guidelines, Timing, and Resistance Stewardship
Apply Dimethomorph preventively or at the earliest visible sign of oily translucent water-soaked spots. Ensure thorough spray coverage utilizing calibrated hollow-cone nozzles.
Because CAA fungicides operate through a single-site mode of action, continuous applications can select for resistant pathogen strains. Always rotate or tank-mix with multi-site contact protectants like Mancozeb or Chlorothalonil.
- Spraying window: Apply during cool, humid weather favorable to downy mildew sporulation
- Water volume: 500 to 750 liters per hectare to ensure complete canopy wetting
- Resistance strategy: Limit to 2-3 applications per season; alternate with FRAC Group M protectants
- Operator safety: Wear rubber gloves, eye goggles, and protective apparel during mixing
Official source
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Central Insecticides Board and Registration Committee (CIBRC) ↗Related on KisanPe
Common questions
Why is Dimethomorph specifically effective against Downy Mildew and Late Blight?
Downy mildew and late blight belong to Oomycetes, whose cell walls contain cellulose; Dimethomorph selectively inhibits cellulose synthesis, destroying the pathogen cell walls.
Does Dimethomorph possess curative activity?
Yes, Dimethomorph provides curative and anti-sporulant action, stopping established mycelial growth and preventing sporangia from producing infective zoospores.
Can Dimethomorph be mixed with Mancozeb?
Yes, co-applying Dimethomorph with Mancozeb is a recommended anti-resistance practice that pairs systemic translaminar control with broad-spectrum contact protection.
General guidance, not personal advice. For your farm, ask your local Krishi Vigyan Kendra or agriculture officer.
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