Chemical Class and Multisite Contact Mode of Action
Chlorothalonil (tetrachloroisophthalonitrile) belongs to FRAC Group M05 (multisite contact activity). Upon application, it forms an insoluble, weather-resistant protective film across plant foliage.
It acts by binding to glutathione and non-specifically inactivating sulfhydryl groups in essential fungal enzymes involved in glycolysis and cellular respiration. This simultaneous multi-site disruption prevents fungal spore germination and cell division, preventing resistance development.
- FRAC Group M05 Multisite Action: Inactivates multiple cellular enzymes, preventing fungal resistance.
- Broad Protective Barrier: Shields leaves, stems, and fruits before fungal hyphae can penetrate.
- Formulation Type: Wettable Powder (75% WP) providing a tenacious, rainfast foliar shield.
Target Pathogens and Labeled Field Crops
Chlorothalonil 75% WP is officially registered under CIBRC standards for controlling critical disease complexes in potato, tomato, groundnut, and chili. In potato and tomato, it manages early blight (Alternaria solani) and late blight (Phytophthora infestans).
In groundnut, it provides protection against tikka leaf spot (Cercospora arachidicola) and rust; and in chili, it controls anthracnose (fruit rot / dieback), preserving leaf canopy and fruit quality.
- Potato & Tomato Blights: Prevents zoospore germination and concentric ring lesion spread.
- Groundnut Tikka Defense: Protects green leaf area to maximize pod development and kernel weight.
- Chili Anthracnose Care: Suppresses sunken water-soaked fruit lesions during humid weather.
Application Guidelines and Resistance Stewardship
Apply Chlorothalonil 75% WP preventively before rainfall or at the earliest visual appearance of disease lesions. Maintain good tank agitation during spraying to keep the wettable powder evenly suspended.
Because of its multisite contact mode of action, Chlorothalonil is an ideal tank-mix partner or rotation component with single-site systemic fungicides (such as triazoles or strobilurins) to delay pathogen resistance development.
- Preventive Timing: Spray at early vegetative stages before fungal lesions spread across the canopy.
- Agitation: Ensure continuous spray tank agitation to maintain uniform chemical suspension.
- Pre-Harvest Interval (PHI): Observe recommended harvest waiting windows as prescribed on the product label.
Official source
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Central Insecticides Board & Registration Committee (CIBRC) ↗Related on KisanPe
Common questions
What type of fungicide is Chlorothalonil 75% WP?
Chlorothalonil 75% WP is a broad-spectrum multisite contact protective fungicide belonging to the chloronitrile chemical group.
Why is Chlorothalonil effective against a broad range of diseases?
It binds to essential sulfhydryl enzymes across multiple metabolic pathways, preventing spore germination across diverse fungal groups.
Can Chlorothalonil 75 WP be mixed with systemic fungicides?
Yes, it is widely tank-mixed or alternated with systemic fungicides (like triazoles or strobilurins) to provide external protection and prevent chemical resistance.
General guidance, not personal advice. For your farm, ask your local Krishi Vigyan Kendra or agriculture officer.
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