Isoprothiolane 40% EC: A Comprehensive Guide to a Thiolcarbamate Systemic Fungicide

Isoprothiolane 40% EC (Emulsifiable Concentrate) is a highly effective systemic fungicide formulated with 400 grams of active ingredient per liter. Belonging to the thiolcarbamate class, it is specifically designed to control rice blast (Pyricularia oryzae), one of the most destructive fungal diseases in rice cultivation. The EC formulation offers excellent solubility in organic solvents, forming a stable emulsion when diluted with water, which ensures uniform coverage and absorption by plants.

Chemical Properties

Item	Details
Common Name	Isoprothiolane
Chemical Name	S – 1,3 – Dimethylbutyl O – isopropyl thiocarbonate
Molecular Formula	C₁₂H₂₃O₂PS
Molecular Weight	262.35 g/mol
CAS No.	24074 – 50 – 2
Physical State	Colorless to light yellow liquid at room temperature
Solubility	Sparingly soluble in water (12 mg/L at 20°C); highly soluble in organic solvents (e.g., acetone, xylene)
Melting Point	-45°C

Mode of Action

Systemic Activity & Translocation

Root & Foliar Absorption: Isoprothiolane is absorbed by rice plants through roots and leaves, then translocated acropetally (upward) via xylem vessels to new growth tissues (shoots, leaves, and panicles).
Long – Lasting Protection: Its systemic nature provides residual activity for 10–14 days, protecting plants from both existing and emerging fungal infections.

Mechanism of Fungicidal Action

Inhibition of Lipid Peroxidation: The active ingredient disrupts the biosynthesis of polyunsaturated fatty acids in fungal cells, leading to lipid peroxidation and damage to cell membranes.
Disruption of Spore Germination: It inhibits the formation of appressoria (infection structures) in Pyricularia oryzae, preventing spores from penetrating plant tissues.

Spectrum of Activity & Application Guide

Crop	Target Diseases	Application Rate	Application Method	Optimal Timing
Rice	Rice blast (leaf, neck, node blast)	150–200 g a.i./ha	Foliar spray (2–3 times per season)	1st spray at tillering stage; 2nd at panicle initiation; 3rd at early heading stage
Other Grasses	Blast – like fungal diseases	100–150 g a.i./ha	Foliar spray	At first sign of disease or as preventive measure

Formulation Features & Advantages

Emulsifiable Concentrate (EC) Benefits:
- High dispersion in water, reducing spray nozzle clogging.
- Quick absorption by plant cuticles, minimizing wash – off by rain.
Environmental & Toxicological Profile:
- Low acute toxicity (LD₅₀ for rats: >2000 mg/kg oral), classified as “slightly toxic” by WHO.
- Moderate persistence in soil (half – life: 1–2 months), with low risk of groundwater contamination when used as directed.

Resistance Management & Safety Precautions

Resistance Prevention:
- Avoid consecutive single – site applications; rotate with other classes (e.g., strobilurins, azoles).
- Mix with contact fungicides (e.g., mancozeb) to broaden efficacy and delay resistance development.
Safety Measures:
- Wear protective clothing, gloves, and goggles during application.
- Avoid spraying in windy conditions or near water bodies to prevent drift and aquatic toxicity.

Global Market & Regulatory Status

Major Use Regions: Widely used in Asia (China, India, Japan), Southeast Asia, and Africa, where rice is a staple crop.
Regulatory Approvals: Registered in major rice – producing countries, including compliance with FAO standards for agricultural use.

Comparison with Similar Fungicides

Fungicide	Class	Main Target Crop	Mode of Action	Residue Period
Isoprothiolane 40% EC	Thiolcarbamate	Rice	Lipid peroxidation inhibition	10–14 days
Tricyclazole	Triazole	Rice	Ergosterol biosynthesis inhibition	7–10 days
Pyraclostrobin	Strobilurin	Multiple crops	Respiration chain inhibition	14–21 days

Environmental Impact & Sustainability

Ecotoxicity:
- Moderate toxicity to fish and aquatic invertebrates (LC₅₀ for fish: 0.1–1 mg/L), requiring buffer zones near water bodies.
- Low toxicity to bees and birds when used as per label instructions.
Sustainable Practices:
- Integrated Pest Management (IPM) programs often include isoprothiolane as a key component for rice blast control, balancing efficacy with environmental safety.

This comprehensive overview combines chemical properties, application guidelines, and safety considerations to provide a practical reference for agricultural use of Isoprothiolane 40% EC.