Compound application of chitosan oligosaccharide in agriculture

What is chitosan oligosaccharide?

Chitosan oligosaccharides are a mixture of oligosaccharides composed of 2-10 glucosamine molecules linked by β-1,4-glycosidic bonds.
Simply put, they are products with smaller molecular weights obtained through the further degradation of the natural polysaccharide chitosan. Chitosan itself originates from chitin, the second most abundant polysaccharide in nature (after cellulose).

We can understand its origin through a visual “decomposition chain”:
Marine shrimp and crab shells → Chitin → Chitosan → Chitosan oligosaccharides

This process can be understood as follows:

• Chitin: The core component of shrimp and crab shells, insoluble in water, acids, and alkalis, making it difficult to utilize directly.

• Chitosan: Obtained from chitin through deacetylation, it is soluble in dilute acids and has a wider range of applications, but its molecular weight remains relatively large.

• Chitosan oligosaccharides: Chitosan is “cut” into smaller fragments through biological enzymes or chemical methods. It is this “cutting” process that gives it water solubility and extremely high biological activity.

Why is it so powerful?

The many functions of chitosan oligosaccharides stem from their unique physicochemical properties:

1.Small molecular weight and good water solubility: This is the most fundamental difference between it and chitosan. Its molecular weight is typically below 3000 Daltons, making it completely soluble in water, convenient to use, and easily absorbed by organisms.

2.Unique positive charge: Under acidic or neutral conditions, the amino groups (-NH₂) on the chitosan oligosaccharide molecular chain protonate, acquiring a positive charge (-NH₃⁺).

3.Biocompatibility and biodegradability: Derived from nature, it returns to nature, is environmentally friendly, and safe and non-toxic to humans and animals.

Why is chitosan oligosaccharide so widely applicable in compound formulations?

This is precisely the core reason why chitosan oligosaccharides are so highly regarded in agriculture. Its extremely wide range of compound applications is determined by its unique mechanism of action, natural physicochemical properties, and extremely high safety.

We can summarize it in one sentence: chitosan oligosaccharides are not “soldiers” that directly kill enemies (pathogens/pests), but rather “instructors” and “coordinators” that activate the plant’s own defense system and improve its internal environment. This unique role allows it to work synergistically with almost all types of “soldiers.”

1. Unique Mechanism of Action: Based on “Induced Immunity” Rather Than “Direct Killing”

This is the most fundamental reason.

Most pesticides/fungicides: act by “direct killing,” killing pathogens or pests by interfering with specific physiological processes (such as respiration and nerve conduction). This method easily leads to resistance, and different agents may compete or antagonize each other.

Chitosan oligosaccharides: They themselves do not have direct or only weak fungicidal/insectic activity. Their core function is as an “elicitor” or “signaling molecule.”

Mimetic Invasion: When chitosan oligosaccharides come into contact with plants, the plants “mistakenly” believe that pathogens (such as fungi, because chitosan oligosaccharides are derived from chitin, a component of fungal cell walls) have invaded.

Activated Defense: The plant then rapidly activates a powerful immune system, including:

1. Producing Phytoprotectants: Synthesizing substances with antibacterial activity.
2. Depositing Callose: Thickening the inner side of the cell wall, forming a physical barrier.
3. Activating Defense Genes: Preparing for a counterattack.
4. Systemic resistance: This defensive state can be transmitted throughout the entire plant, achieving “early warning at one point, systemic defense.”

Because chitosan oligosaccharides do not directly participate in “toxicity,” they do not compete with chemical pesticides for targets. Instead, they create a better operational environment for chemical pesticides (healthy plants), achieving perfect functional complementarity.

2. Multi-target and Multifunctional Characteristics

Chitosan oligosaccharides offer multifaceted benefits to crops, providing numerous binding points for compound formulations.

• Immune Boosting: As mentioned above, this is the core function.

• Growth Promotion: It can regulate the levels of endogenous plant hormones (such as auxins and cytokinins), promoting root development and plant growth.

• Soil Improvement: It promotes the reproduction of beneficial soil microorganisms (such as actinomycetes) and inhibits harmful bacteria.

• Film Formation and Adsorption: It possesses certain adhesive and film-forming properties, forming a protective film on plant or seed surfaces. It also acts as a carrier, improving the adhesion and absorption rate of other pesticides and fertilizers.

• Nutritional Supplementation: Its degradation products are natural carbon and nitrogen-containing nutrients.

This multi-functional characteristic means that whether you want to treat diseases, control pests, promote growth, strengthen roots, or improve quality, chitosan oligosaccharides can find suitable partners, contributing value from different angles.

3. Excellent Physical and Chemical Compatibility

• Good Water Solubility and Stability: Chitosan oligosaccharides are readily soluble in water, allowing for easy mixing with most water-based pesticides and fertilizers.

• Wide pH Adaptability: Highly stable under weakly acidic to neutral conditions, matching the pH range of most agricultural formulations.

• Molecular Size and Activity: The molecular weight of its oligosaccharides is moderate, allowing for plant recognition without being too large to hinder the penetration and absorption of other components.

4. Extremely High Safety and Environmental Friendly

• Natural Source: Derived from chitin in the shells of marine shrimp and crabs, it is a natural biopolymer.

• Non-toxic and Harmless to Humans and Animals: Practically non-toxic, making it very safe to use.

• Easily Degradable and Residue-Free: Biodegradable in the environment without causing pollution.

• No Harm to Plants: Safe for crops at recommended dosages, with no risk of phytotoxicity.

This extremely high safety profile means that when combined with biological agents and sensitive growth regulators, the risk is extremely low, preventing unintended harm.

What can chitosan oligosaccharide be combined with?

1.Core Principles of Compound Formulation

• Synergistic Effect: When combined with other substances, it compensates for the shortcomings of a single component, acting on crops through different pathways for a more comprehensive and lasting effect.

• Functional Complementarity: Chitosan oligosaccharides primarily stimulate the plant’s own immune system, while other agents directly kill bacteria and insects; the combination provides both internal and external treatment.

• Reduced Resistance: Reduces the amount of chemical pesticides used, delaying the development of pesticide resistance in pathogens and pests.

• Safety: Prioritizes compounding with low-toxicity and environmentally friendly components from biological and mineral sources, aligning with the development direction of green and organic agriculture.

2. Main Compound Formulation Schemes and Applications

Compounding with Chemical Pesticides (Most Commonly Used)

This is currently the most widely used method, aiming to reduce the amount of chemical pesticides used and improve efficacy.

Compatible with Fungicides:

• Target Pesticides: Azoxystrobin, pyraclostrobin, tebuconazole, difenoconazole, etc.
• Mechanism of Action: Chemical fungicides directly inhibit or kill pathogens; chitosan oligosaccharides stimulate plants to produce phytoalexins, callose, and other disease-resistant substances, blocking pathogen invasion. Simultaneously, the film-forming properties of chitosan oligosaccharides can delay pesticide runoff.
• Application Scenarios: Control of fungal diseases such as powdery mildew, downy mildew, anthracnose, and leaf spot. It can reduce chemical pesticide use by 20%-30% compared to conventional application rates.

Compatible with Insecticides:

• Target Pesticides: Abamectin, imidacloprid, thiamethoxam, etc.
• Mechanism of Action: Chemical insecticides directly poison and kill pests; chitosan oligosaccharides can induce plants to produce signaling molecules such as jasmonic acid, activating defense mechanisms and releasing or accumulating substances harmful to pests (such as protease inhibitors), thus reducing the palatability of crops to pests.
• Application Scenarios: Control of aphids, whiteflies, mites, and other piercing-sucking pests.

Combination with Virus Inhibitors:

• Combined with: Moroxydine hydrochloride, amino oligosaccharides, mushroom proteoglycans, etc.
• Mechanism of Action: Chitosan oligosaccharides are excellent virus disease inducers, strongly inducing systemic resistance in plants and inhibiting virus replication and spread. Combined use with virus inhibitors is significantly more effective than using them alone.
• Application Scenarios: Control of tobacco mosaic virus, tomato yellow leaf curl virus, watermelon mosaic virus, etc.

2. Combined with Biological Agents (Golden Partner)

This is an ideal combination for developing green and organic agriculture.

• Target Microorganisms: Beneficial microorganisms such as Bacillus subtilis, Bacillus amyloliquefaciens, Trichoderma, and Bacillus brevis.

• Mechanism of Action:

“Food” and “Weapon”: Chitosan oligosaccharides can serve as “food” (carbon and nitrogen source) for beneficial bacteria, promoting their rapid reproduction and colonization.

Synergistic Disease Resistance: Chitosan oligosaccharides activate plant immunity, while beneficial bacteria directly inhibit soil-borne pathogens through competition, antagonism, and parasitism. Both build a healthy defense line for crops at different levels.

Promoting Root Development: Both stimulate crop root development, forming a strong root system.

• Application Scenarios:

Seedling Stage: Root dipping or drenching to prevent damping-off and seedling blight, and cultivate strong seedlings.

Growth Stage: Root drenching to control soil-borne diseases such as wilt, bacterial wilt, and root rot, while improving soil microecology.

3. Combined with biostimulants such as alginic acid/amino acids/humic acid

This combination focuses on promoting crop growth, enhancing stress resistance, and improving quality.

• Mechanism of Action:

Chitosan oligosaccharides: Regulate endogenous hormone levels in plants, open stomata in crop leaves, and enhance nutrient absorption.

Alginic acid/amino acids: Provide abundant organic nutrients and natural active substances, directly participating in crop metabolism.

Humic acid: Improves soil, chelates nutrients, and stimulates root growth.

Synergistic Effects: The combination of these three ingredients demonstrates excellent performance in promoting root growth, strengthening seedlings, protecting flowers and fruits, and enhancing crop resistance to cold, drought, and waterlogging. It also significantly improves fruit sugar content, color, and firmness.

• Application Scenarios:

Can be used throughout the entire growth period, but is particularly effective before flowering, after fruit set, during color change, and before or after encountering adverse conditions (such as low temperatures or drought).

4. Compounding with Micronutrient Fertilizers

• Mechanism of Action: Chitosan oligosaccharides possess excellent film-forming and adsorption properties, acting as a “carrier” for micronutrients, thus improving the adhesion rate and absorption efficiency of foliar fertilizers. Simultaneously, it activates the rhizosphere soil, releasing fixed micronutrients (such as calcium, magnesium, zinc, and iron) for crop absorption.

• Application Scenarios: Prevention and treatment of crop nutrient deficiencies, such as blossom-end rot (calcium deficiency) and little leaf disease (zinc deficiency). When compounded with calcium fertilizer, it can significantly improve fruit firmness and reduce fruit cracking.

In summary, chitosan oligosaccharides have enormous potential for compounding in agriculture, serving as a powerful tool for reducing pesticide use while increasing efficiency and promoting green farming.

For reducing pesticide use and increasing efficiency: prioritize compounding with chemical pesticides.

For green/organic agriculture: prioritize compounding with biological agents.

For improving quality, increasing yield, and enhancing stress resistance: prioritize compounding with alginic acid/amino acids/humic acid.