Classification by Movement & Mode of Action
Fungicides are fundamentally categorized into contact (protectant) and systemic (eradicant/curative) molecules, reflecting how they interact with plant surfaces and vascular tissues.
Contact fungicides form a protective chemical shield on outer plant surfaces to prevent spore germination, whereas systemic fungicides penetrate plant tissues and translocate through xylem vessels to arrest fungal mycelium inside leaves.
- Contact (Protectant) Fungicides: Remain on plant surfaces (e.g., Mancozeb, Copper Oxychloride, Sulphur); protect against spore penetration
- Systemic (Curative) Fungicides: Translocate internally through plant vascular systems (e.g., Carbendazim, Hexaconazole, Azoxystrobin, Metalaxyl)
- Translaminar Fungicides: Penetrate through the leaf blade from upper to lower surfaces without long-distance vascular movement
- Multi-Site vs Single-Site: Multi-site contacts disrupt multiple enzymes with zero resistance risk; single-site systemics target specific fungal enzymes
FRAC Code System & Resistance Management
The Fungicide Resistance Action Committee (FRAC) assigns distinct numerical codes to active ingredients based on their target biochemical site in fungi (e.g., respiration, sterol biosynthesis, cell division, or nucleic acid synthesis).
Repeated use of fungicides from the same FRAC group exerts selective pressure that leads to resistant fungal strains. Farmers must alternate chemical groups across the crop season to maintain disease control.
- FRAC Group 3 (DMI Triazoles): Inhibit ergosterol biosynthesis (e.g., Propiconazole, Tebuconazole, Difenoconazole)
- FRAC Group 4 (Phenylamides): Inhibit RNA polymerase-I in Oomycetes (e.g., Metalaxyl-M)
- FRAC Group 11 (QoI Strobilurins): Inhibit mitochondrial respiration at complex III (e.g., Azoxystrobin, Pyraclostrobin)
- FRAC Group M (Multi-Site Contacts): Low resistance risk protectants (e.g., Mancozeb M03, Copper M01, Sulphur M02)
Application Timing & Spray Precision
Fungicides deliver maximum return when applied preventatively or at the earliest onset of disease symptoms. Once fungal necrosis destroys photosynthetic leaf tissue, curative fungicides cannot restore dead cells.
Utilize fine-droplet hollow-cone nozzles operating at recommended pressure to coat the undersides of leaves and dense inner canopies where fungal microclimates flourish.
- Weather Monitoring: Apply ahead of prolonged cloudy, high-humidity, or drizzly conditions that trigger fungal sporulation
- Coverage: Ensure thorough droplet coverage on lower leaf surfaces where spores often germinate
- Safety & Waiting Period: Strictly observe statutory pre-harvest intervals (PHI) to prevent export and domestic residue violations
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 (CIBRC) ↗Related on KisanPe
Common questions
What is the difference between contact and systemic fungicides?
Contact fungicides remain on the leaf surface to kill fungal spores before they infect; systemic fungicides penetrate inside plant tissues to stop fungal growth that has already entered.
What does the FRAC code on a fungicide label mean?
The FRAC code identifies the specific biochemical mode of action; rotating between different FRAC codes prevents fungal pathogens from developing chemical resistance.
Can a fungicide cure plant leaves that have already turned brown and dead?
No, fungicides can stop the fungus from spreading to healthy tissues, but they cannot restore or regenerate leaf cells that have already died from necrosis.
General guidance, not personal advice. For your farm, ask your local Krishi Vigyan Kendra or agriculture officer.
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