Active ingredient and multi-site mode of action
Chlorothalonil (tetrachloroisophthalonitrile) is classified under FRAC Group M05. It binds to and deactivates cellular glutathione and thiol enzymes involved in fungal cell respiration. Because it attacks multiple biochemical pathways simultaneously, fungal pathogens cannot easily develop resistance.
- Active constituent: Chlorothalonil 75% WP (wettable powder)
- Chemical class: Chloronitrile multi-site contact protectant (FRAC Group M05)
- Superior rainfastness: Natural tenacity adheres firmly to leaf waxy cuticles, resisting heavy rain wash-off
Target crops and major fungal diseases
- Potato and tomato: Early blight (Alternaria solani) and late blight (Phytophthora infestans).
- Groundnut: Tikka leaf spot (Cercospora arachidicola) and rust.
- Watermelon and cucurbits: Downy mildew and anthracnose.
- Chili: Fruit rot and leaf spot complexes.
Application timing and resistance stewardship
Chlorothalonil is strictly a preventive fungicide and must be applied before fungal spores germinate on foliage. It serves as an essential resistance management partner when rotated with single-site systemic fungicides (such as strobilurins and triazoles). Always wear protective eye goggles and masks, and adhere to CIBRC pre-harvest intervals.
Official source
Check the latest rules, benefits and forms here. KisanPe is an independent platform and is not a government website.
Central Insecticides Board & Registration Committee ↗Related on KisanPe
Common questions
What is the primary mode of action of Chlorothalonil fungicide?
It acts as a multi-site contact protectant, deactivating fungal thiol enzymes and preventing fungal spore germination.
Can fungal pathogens develop resistance to Chlorothalonil?
Resistance is extremely rare because chlorothalonil disrupts multiple essential enzyme pathways simultaneously.
Why is Chlorothalonil valued for rainfastness?
It bonds naturally with leaf wax layers, resisting wash-off by monsoon rains significantly better than many other contact protectants.
General guidance, not personal advice. For your farm, ask your local Krishi Vigyan Kendra or agriculture officer.
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