Trichoderma Harzianum Uses: T-22 Strain, Products, Price and Complete Grower’s Guide
Soil-borne diseases are among the hardest problems a grower faces. You can’t see them until the damage is done: seedlings collapse, roots turn brown, tubers rot in storage. Chemical fungicides help, but they cost money, leave residues, and pathogens can build resistance over time. That is why so many farmers, nursery owners and home gardeners are turning to trichoderma harzianum, a naturally occurring fungus that protects roots and improves soil health at the same time.
This guide covers what T. harzianum is, how it works, where it is used, how the famous T-22 strain differs from other strains, what it looks like under a microscope, and what affects its price. It also has practical tables and FAQs, so you can use it as a working reference.
What Is Trichoderma Harzianum?
Trichoderma harzianum is a free-living fungus found in soils around the world, especially in the root zone of plants and in decaying organic matter. It is a “friendly” fungus: it doesn’t harm crops, and it attacks and outcompetes many of the fungi that do.
Scientists have known about its ability to suppress plant diseases for decades. Today it is one of the most commonly used biocontrol agents in agriculture, and it is sold as a biofungicide, a biostimulant and a soil conditioner, sometimes all three on the same label.
You will often see it written as T. harzianum or t harzianum in research papers and product catalogues. All of these refer to the same species.
Trichoderma Harzianum Common Name
T. harzianum doesn’t really have a single, universally accepted common name like “neem” or “marigold.” In practice, people call it:
- Trichoderma (the genus name, used loosely for the whole group)
- Biocontrol fungus or friendly soil fungus
- Bio-fungicide (when referring to the products)
- Root-zone fungus (informally, in horticulture)
Its sexual (teleomorph) stage is classified under Hypocrea. One thing worth knowing: modern DNA studies show that “T. harzianum” is actually a species complex, and some strains once labelled T. harzianum have since been reassigned to closely related species. For farmers this rarely changes how the product performs, but it explains why you may see different species names in newer scientific papers.
Trichoderma Harzianum Morphology
Identification matters if you work in a lab, produce your own culture, or want to confirm what you’ve isolated. Here is what T. harzianum looks like:
| Feature | Description |
|---|---|
| Colony on PDA (potato dextrose agar) | Grows fast. Starts white and cottony, then turns green as spores develop, often in rings or patches |
| Hyphae | Colorless (hyaline), thin, septate (divided by cross walls) and branched |
| Conidiophores | Branched, often in a pyramid-like pattern |
| Phialides | Flask-shaped, arranged in whorls at the branch tips |
| Conidia (spores) | Small, round to slightly oval, smooth-walled, green; roughly 2.5–3.5 µm |
| Chlamydospores | Thick-walled resting spores, formed in older cultures and helpful for survival in soil |
| Smell | Some cultures give off a faint coconut-like odor |
The fast growth and heavy green sporulation are what make T. harzianum so good at colonizing roots and crowding out slower-growing pathogens.
How Trichoderma Harzianum Works
Trichoderma doesn’t rely on one trick. It uses several at the same time, which is one reason it is hard for pathogens to “resist” it.
- Competition. It grows quickly and uses up the nutrients and space around roots, leaving little for harmful fungi.
- Mycoparasitism. It coils around pathogen hyphae and releases enzymes (chitinases and glucanases) that break down their cell walls.
- Antibiosis. It produces natural compounds that slow or stop other fungi from growing.
- Induced resistance. It signals the plant to switch on its own defenses, so the whole plant is better prepared for attack.
- Growth promotion. Colonized roots often grow denser and deeper, take up nutrients more efficiently and cope better with stress such as drought or salinity.
Trichoderma Harzianum Uses in Agriculture
The main uses fall into a few categories. Here are the most important ones:
- Disease control (biofungicide). This is its best-known role. It helps manage damping-off, root rot, wilt, crown rot and stem canker caused by soil-borne fungi.
- Seed and tuber treatment. Coating seeds, tubers or bulbs lets the fungus colonize the root zone from day one.
- Soil application. Mixed into furrows, planting holes, nursery beds, or applied as a drench or through drip irrigation.
- Root dip. Seedlings of vegetables, rice, tobacco and ornamentals are dipped before transplanting.
- Composting. Added to compost or farmyard manure, it speeds up decomposition of crop residues and enriches the final product with beneficial spores.
- Greenhouse and hydroponics. Used in potting mixes, rockwool and nutrient systems to protect young plants.
- Plant growth support. Many growers use it mainly for stronger roots and better establishment, with disease protection as a bonus.
- In addition to suppressing soil-borne fungal pathogens, applying Trichoderma harzianum near the root zone works effectively as part of an integrated strategy for nematodes & their management without relying solely on chemical nematicides.
Trichoderma Harzianum Uses by Crop and Disease
| Crop | Main problems it helps with | Typical method |
|---|---|---|
| Potato | Fusarium dry rot, black scurf and stem canker (Rhizoctonia), Pythium | Tuber treatment, in-furrow |
| Tomato, pepper, eggplant | Damping-off, Fusarium wilt, root rot | Nursery soil mix, root dip, drench |
| Cucumber, melon, squash | Pythium root rot, crown rot | Soil drench, seed treatment |
| Beans, peas, chickpea | Root rot, wilt | Seed treatment |
| Cotton | Seedling disease, wilt | Seed treatment |
| Rice | Sheath blight, seedling diseases | Seed treatment, root dip |
| Onion, garlic | White rot, basal rot | Soil application |
| Strawberries, berries | Root and crown rots, Botrytis | Drench, drip |
| Turf, ornamentals | Pythium, Rhizoctonia | Soil mix, drench |
Trichoderma Harzianum Uses as a Fungicide
As a biofungicide, T. harzianum works best as a preventive tool. It needs time to establish itself in the root zone, so applying it before disease shows up gives the best results.
Pathogens it targets
- Pythium (damping-off, root rot)
- Rhizoctonia solani (stem canker, black scurf, sheath blight)
- Fusarium species (wilts, dry rot, crown rot)
- Sclerotinia and Sclerotium rolfsii (white mold, southern blight)
- Botrytis (gray mold) in some conditions
- Verticillium (wilt) in some systems
Biofungicide vs. chemical fungicide
| Factor | Trichoderma harzianum | Chemical fungicide |
|---|---|---|
| How it works | Competes with, parasitizes and suppresses pathogens; boosts plant defenses | Poisons or inhibits the pathogen |
| Timing | Best used preventively | Preventive or curative, depending on product |
| Residue | Generally none of concern | Possible residues and waiting periods |
| Resistance risk | Low (multiple modes of action) | Moderate to high with repeated use |
| Soil life | Supports beneficial microbes | Can reduce microbial diversity |
| Speed | Slower to establish | Often faster, especially curative |
| Extra benefits | Root growth, nutrient uptake, stress tolerance | None |
| Fit for organic systems | Many products are approved (check local rules) | Usually not |
Neither is “better” in every situation. In a severe outbreak, a chemical may be needed. For ongoing, long-term protection and soil health, biologicals make a lot of sense, and many growers use both in an integrated program.
Trichoderma Harzianum T-22 (T22 Trichoderma)
If you’ve searched for “t22 trichoderma” or “trichoderma harzianum t 22,” you’ve likely come across one of the best-known strains in the world.
T-22 (also called strain KRL-AG2) was developed in the 1980s at Cornell University by combining two parent strains of T. harzianum through protoplast fusion. The aim was to create a strain with excellent rhizosphere competence, meaning it can colonize and persist on roots as they grow, rather than only surviving in the soil near the seed.
Why T-22 became so popular:
- It colonizes the entire root system and keeps growing along with the root.
- It is effective against Pythium, Rhizoctonia, Fusarium and others.
- It has been shown to improve root development and plant vigor.
- It has been registered as a biopesticide in several countries and widely used in greenhouses, nurseries, turf and field crops.
Not every Trichoderma product contains T-22. Many other strains of T. harzianum (and other Trichoderma species) are also sold, and some perform very well in specific crops or climates. Check the label for the strain name and spore count rather than assuming.
T-22 vs. general T. harzianum products
| Point | T-22 strain | Other T. harzianum strains |
|---|---|---|
| Origin | Cornell University, fusion of two parent strains | Natural isolates from soil or plants, or other selections |
| Strength | Strong root colonization over time | Varies by strain; some are adapted to local soils |
| Documentation | Extensive research and field data | Varies; reputable brands publish strain data |
| Availability | Sold under specific commercial brands | Sold widely as powders, granules, liquids |
| What to check | Strain name and licensed source | Strain ID, CFU count, shelf life |
Trichoderma Harzianum Products
You’ll find T. harzianum sold in several forms. The right choice depends on your crop, scale and application method.
| Form | Best for | Pros | Cons |
|---|---|---|---|
| Wettable powder (WP) | Seed treatment, drench, foliar in some cases | Easy to store and mix; widely available | Needs good mixing; dust, so wear a mask |
| Granules | Soil and potting mix | Even distribution; easy to apply | Higher bulk; usually pricier |
| Liquid or suspension | Drip systems, drenching, large operations | Quick to apply; mixes evenly | Shorter shelf life; may need cool storage |
| Talc-based formulation | Seed coating, small farms | Cheap and easy | Variable quality between suppliers |
| Water-dispersible granules (WDG) | Commercial growers | Convenient, dust-free | Usually higher cost |
Commercial formulations of the Trichoderma biofungicide such as HarzShield make it easy for growers to include these benefits in their farms. These biological fungicides provide an eco-friendly alternative to conventional chemical treatments.
How to choose a good product
When you’re comparing options, look for these on the label:
- Species and strain name. “Trichoderma” alone is vague.
- Spore count (CFU per gram or ml). Higher isn’t always better, but very low counts are a red flag.
- Manufacturing and expiry date. Live fungi lose viability over time.
- Crops and pathogens listed. Matches your situation.
- Registration status where you farm, where required.
- Storage instructions. Good suppliers give clear guidance.
Selecting the right biological fungicide is very important for achieving reliable results. A product with viable spores that is compatible with your seed treatment and soil practices will almost always outperform a cheaper one with dead or low-count spores.
Trichoderma Harzianum Price: What to Expect
Price is one of the most searched questions, and the honest answer is that it varies a lot by country, formulation, strain, spore concentration, brand and pack size. Rather than quote numbers that go out of date quickly, here is what drives the price and how to compare fairly:
| Factor | How it affects price |
|---|---|
| Formulation | Basic powders and talc-based products are usually cheapest; granules, WDG and liquids cost more |
| Spore concentration (CFU) | Higher and better-verified counts generally cost more |
| Strain | Patented or well-documented strains (such as T-22) often carry a premium |
| Brand and quality control | Reputable manufacturers invest in testing and consistent production |
| Pack size | Bulk sacks work out much cheaper per kg than small retail packs |
| Import duties and shipping | Can add a lot, especially for liquids and temperature-sensitive products |
| Registration and certification | Registered or organic-certified products cost more to bring to market |
Rough guide: small garden packs cost more per kilogram, while agricultural bulk packs cost much less. As a very general rule, farm-level powder products are modest in cost per hectare compared with many chemical fungicide programs, but always check current quotes from suppliers in your area.
Tip for comparing: don’t compare price per kilo alone. Compare cost per treated hectare (or acre) using the label dose, and compare the spore count. A cheaper product that needs double the rate may cost more in the end.
How to Use Trichoderma Harzianum: Practical Steps
Always follow the label of the specific product you buy, since rates differ by formulation and spore count. The general approach is:
Seed or tuber treatment
Mix the product with a little water (or use it dry, depending on the label), coat the seed or cut tubers evenly, let them dry in the shade and plant soon after. This is how Trichoderma gets to the root zone early, before pathogens do.
Soil application
Mix the product with well-decomposed compost or farmyard manure, keep it moist for a few days so the fungus starts to grow, then apply it in furrows, planting holes or around the root zone. Don’t use fresh, hot manure. To maximize the benefits of this bio-fungicide, it is highly effective when combined with organic soil builders. Applying it alongside organic practices like green manure helps accelerate the decomposition of organic matter and enriches soil biodiversity.
Drench or drip
Dissolve in water as directed and apply to the root zone. Use clean water and avoid chlorinated water if you can, as chlorine can reduce spore viability.
Nursery and transplant dip
Dip roots of seedlings in a Trichoderma suspension for a short time before transplanting, or mix the product into the nursery bed or potting mix.
Timing
Apply at planting or sowing, and repeat according to the label (often at intervals through the season for high-risk crops).
Growing Healthy Potatoes with Trichoderma
Potatoes are one of the crops where Trichoderma really earns its place. Fusarium, Pythium and Rhizoctonia attack roots, sprouts and tubers, reducing yield, quality and storage life. Chemical fungicides can manage them, but they come with environmental concerns, residue risks and the possibility of resistance.
Healthy soil is the first line of defense. A diverse soil microbiome improves nutrient availability and naturally suppresses harmful pathogens. When soil is disturbed or too dependent on chemicals, beneficial microbes decline and pathogens get a chance to take over.
By colonizing the root zone, T. harzianum competes with harmful fungi, produces enzymes that break down pathogen cell walls, and helps the plant switch on its own defenses. That makes the rhizosphere less welcoming to disease and more supportive of potato growth.
The idea is prevention rather than cure. Establishing beneficial fungi before pathogens take hold lowers disease pressure naturally, in line with regenerative farming principles: fewer chemical inputs, better soil structure and long-term resilience.
Practical ways to use it in potatoes:
- Seed tuber treatment: coating tubers ensures early root colonization.
- In-furrow application: placing it in the planting furrow builds a protective microbial shield around the roots.
- Good agronomy alongside it: crop rotation, proper drainage and disease-free seed all make Trichoderma work better.
Field studies and extension programs commonly report:
- Reduced Fusarium dry rot, leading to healthier tubers and lower storage losses
- Better seedling emergence and root vigor, especially in fields with a history of Pythium damping-off
- Suppression of Rhizoctonia stem canker and black scurf, supporting early growth and tuber development
By taking a proactive approach, growers protect the current crop and improve the soil for future seasons, which makes the land more productive and resilient over time.
Long-Term Benefits Beyond Disease Control
T. harzianum does more than protect against disease. Over time it contributes to healthier, more resilient soil. The fungal network can improve soil structure, helping water retention and nutrient availability. Colonized roots tend to develop stronger defenses and handle environmental stress better. Integrating Trichoderma can also reduce the number of chemical fungicide applications, cutting input costs while keeping yields and quality steady season after season.
Compatibility, Storage and Safety
Compatibility. Trichoderma is a living fungus, so some fungicides can harm it, particularly systemic and broad-spectrum products. As a general rule:
| Product type | Compatibility with Trichoderma |
|---|---|
| Most fertilizers (at normal rates) | Usually compatible |
| Compost and organic matter | Excellent, it feeds the fungus |
| Other biologicals (Bacillus, Pseudomonas) | Often compatible and used together |
| Systemic fungicides | Often not compatible; leave a gap or follow label advice |
| Contact fungicides (copper, sulfur, etc.) | Variable; test or follow label |
| Strong disinfectants and chlorine | Avoid |
Storage. Keep it in a cool, dry place away from direct sunlight, in its original sealed pack. Heat and moisture shorten the life of the spores. Use within the shelf life stated on the label.
Safety. Trichoderma products are generally considered low risk to people, animals and bees, but the dust of any powder can irritate the nose and lungs. Wear a mask and gloves when mixing, and follow the label.
Common Mistakes to Avoid
- Applying it after disease has already spread. It works best as prevention.
- Mixing with fungicides straight away. This can kill the spores.
- Using expired or badly stored product. Dead spores won’t help.
- Dry, sterile soil. Trichoderma needs some moisture and organic matter to establish.
- Expecting overnight results. It builds protection over days and weeks.
- Ignoring the basics. Crop rotation, drainage and clean seed still matter.
Frequently Asked Questions
What is Trichoderma harzianum used for?
It is mainly used as a biofungicide to protect plant roots from soil-borne diseases such as damping-off, root rot, wilt and stem canker. It is also used to promote root growth, improve nutrient uptake and speed up composting.
What is the common name of Trichoderma harzianum?
There is no single official common name. People usually just say “Trichoderma,” or call it a biocontrol fungus, friendly soil fungus or biofungicide.
What does T. harzianum look like?
In culture, colonies are fast-growing, starting white and turning green as spores form. Under a microscope you see branched conidiophores, flask-shaped phialides and small, smooth, green, rounded spores.
What is T-22 Trichoderma?
T-22 is a well-known strain of T. harzianum developed at Cornell University. It is valued for colonizing roots and protecting plants against Pythium, Rhizoctonia, Fusarium and other pathogens.
Is T-22 the same as Trichoderma harzianum?
T-22 is one specific strain within the T. harzianum group. All T-22 products are T. harzianum, but not all T. harzianum products contain T-22.
How much does Trichoderma harzianum cost?
It depends on the formulation, strain, spore count, brand and pack size. Bulk agricultural packs are far cheaper per kilogram than small garden packs. Compare cost per treated area, not just price per pack.
Can Trichoderma harzianum replace chemical fungicides?
In many situations it can reduce the need for them, especially for soil-borne diseases and when used preventively. In severe outbreaks, you may still need a chemical option. Many growers combine both in an integrated program.
When should I apply it?
At sowing or planting, before disease appears. Repeat according to the label for long-season or high-risk crops.
Can I use it with fertilizers and compost?
Yes, it works well with compost and most fertilizers. Avoid applying it at the same time as strong chemical fungicides.
Is it safe for humans, pets and beneficial insects?
It is generally considered low risk, but powders can irritate the airways, so use gloves and a mask and follow the label.
How long does it take to work?
It needs time to colonize roots, so you’ll see the protective effect build over the first couple of weeks. Seed and tuber treatments start working from germination.
Can I use it in organic farming?
Many Trichoderma products are accepted in organic systems, but rules differ by country and certifier, so check before you buy.
How long can I store it?
Usually 6 to 24 months depending on the formulation, if kept cool and dry. Always check the expiry date on the pack.
Does it work in all soils and climates?
It adapts to a wide range of soils, but performs best in moist, organic-rich soil with moderate pH and temperature. Very dry, sterile or extremely hot conditions reduce its effectiveness.
Final Thoughts
Trichoderma harzianum is a practical, proven tool for growers who want healthier roots, stronger plants and a more resilient soil. It isn’t a magic cure, but when you apply it early, store it properly and pair it with good farming practices, it can cut disease losses and reduce your dependence on chemical inputs. Whether you choose the well-studied T-22 strain or another reliable T. harzianum product, check the strain, the spore count and the expiry date, and you’ll be well on your way to a healthier crop.
