Major fungicide classifications and modes of action
- Contact (Protectant) Fungicides: Form a protective surface barrier on leaves and stems; examples include Mancozeb, Copper Oxychloride, and wettable Sulphur. They act on multiple metabolic sites, making fungal resistance practically impossible.
- Systemic (Curative) Fungicides: Penetrate into plant tissues and translocate vascularly to halt established fungal hyphae; examples include Triazoles (Tebuconazole, Propiconazole) and Strobilurins (Azoxystrobin).
- Bio-Fungicides: Beneficial biocontrol microorganisms like Trichoderma viride, Trichoderma harzianum, and Pseudomonas fluorescens that colonize roots and parasitize soil pathogens.
Preventive versus curative disease management
Fungicides deliver maximum efficacy when applied preventively before fungal spores penetrate plant leaf cuticles. For destructive diseases like potato late blight or grape downy mildew, curative spraying after extensive tissue necrosis has set in is rarely fully effective. Regular field scouting and weather monitoring allow proactive protective treatments.
Anti-resistance strategies and FRAC guidelines
- Never rely exclusively on single-site systemic fungicides across consecutive sprays; rotate with different Fungicide Resistance Action Committee (FRAC) mode-of-action groups.
- Tank-mix or alternate systemic chemicals with broad-spectrum multi-site protectants like Mancozeb.
- Adhere to CIBRC registered dosages and observe recommended Pre-Harvest Intervals (PHI).
Official source
Check the latest rules, benefits and forms here. KisanPe is an independent platform and is not a government website.
Directorate of Plant Protection, Quarantine & Storage (CIBRC) ↗Related on KisanPe
Common questions
What is the key functional difference between contact and systemic fungicides?
Contact fungicides remain on outer plant surfaces to prevent spore entry, while systemic fungicides enter plant vascular tissues to protect new growth and suppress existing infections.
How do bio-fungicides like Trichoderma suppress soil-borne fungal diseases?
Trichoderma species produce antifungal antibiotics, physically parasitize pathogen mycelia (like Fusarium and Rhizoctonia), and stimulate host plant resistance.
Can fungicides be sprayed during light rain?
No. Rain washes away contact protectants before they dry; always apply when foliage is dry and expect at least 2 to 3 rain-free hours for chemical adhesion.
General guidance, not personal advice. For your farm, ask your local Krishi Vigyan Kendra or agriculture officer.
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