Can biochar and friendly microbes protect brinjal from Phomopsis blight? What a 2026 trial found
Phomopsis blight rots brinjal fruit and can cut the harvest badly. A 2026 study co-authored by Dr. Abhishek Mathur tested biochar, the beneficial fungus Trichoderma and the beneficial bacterium Pseudomonas against it in pots. Here is what it found, and what it did not show.
Key points
- In a pot trial in Punjab, brinjal plants were infected with the Phomopsis blight fungus and grown with biochar, Trichoderma, Pseudomonas or their combinations.
- The best treatment, 3% biochar with Trichoderma and Pseudomonas, cut disease severity from 71% to 22% and gave about twice the yield of untreated plants.
- Biochar alone at 3–3.5% controlled the disease almost as well. Less biochar (2%) or more (4%) worked clearly less well.
- Trichoderma alone reduced the disease; Pseudomonas alone made no clear difference to it. This was one pot trial, not a field result.
- What to do today: start with clean, treated seed and healthy seedlings, remove infected fruit, and use registered Trichoderma or Pseudomonas products as your KVK advises.
Phomopsis blight: a serious brinjal disease
Phomopsis blight is caused by the fungus Phomopsis vexans. It can kill seedlings in the nursery, causes spots on leaves and cankers on stems, and rots the fruit: sunken, pale spots grow into rings until the fruit decays or dries up. Warm, humid weather favours it, and the paper cites harvest losses of 30 to 50%. The fungus is carried on seed and in old crop debris.
The study tested three tools against it. Biochar is a charcoal made by heating plant material with little air, then mixed into soil. Trichoderma harzianum is a beneficial soil fungus, and Pseudomonas fluorescens a beneficial bacterium; both are sold in India as bio-agents against crop diseases. The idea was that biochar might help these microbes work, and help the plant switch on its own defences.
What the researchers tested
The study was published in 2026 in Plant Science Today. Its authors are Manthur S. Manjunath, Adesh Kumar and Vipul Kumar of Lovely Professional University, Punjab; Sunil Kashyap of the Punjab Agricultural University regional station at Gurdaspur; and Dr. Abhishek Mathur, the fifth author, who helped interpret the results for practical, industrial use.
- Confirmed the cause: they isolated the fungus from rotting brinjal fruit and showed that it caused the disease in healthy plants.
- Mixed biochar into pot soil at 2, 2.5, 3, 3.5 and 4% of the soil's weight. At 3%, that is 165 g of biochar in a 5.5 kg pot.
- Added the microbes: a week after planting 20-day-old seedlings, Trichoderma, Pseudomonas or both were applied, alone or with 3% biochar.
- Infected the plants with the blight fungus at 30 days and kept them humid for two days so the disease could take hold.
- Measured disease severity, plant height, flowering, fruits and yield, soil pH and salts, and the plants' defence chemicals, with three repeats of each treatment and a statistical test.
What they found
The right amount of biochar sharply reduced the disease, and the three-way mix gave the biggest harvest. Untreated plants had a disease severity of 71%. With 3% biochar plus both microbes it was 22%, and with biochar alone at 3.5% or 3% it was 24% and 27%. Statistically, these three were not clearly different from each other.
| Treatment | Disease | Fruits per plant | Yield (untreated = 100) |
|---|---|---|---|
| Untreated soil | 71% | 6.0 | 100 |
| Sterilised soil | 42% | 4.3 | 78 |
| Sterilised soil + biochar 3% | 38% | 6.0 | 102 |
| Biochar 2% | 51% | 7.0 | 107 |
| Biochar 2.5% | 40% | 6.3 | 113 |
| Biochar 3% | 27% | 7.3 | 160 |
| Biochar 3.5% | 24% | 9.3 | 185 |
| Biochar 4% | 53% | 6.3 | 143 |
| Trichoderma | 47% | 6.0 | 162 |
| Pseudomonas | 62% | 5.3 | 148 |
| Trichoderma + Pseudomonas | 53% | 6.7 | 173 |
| Biochar 3% + Trichoderma | 38% | 7.7 | 199 |
| Biochar 3% + Pseudomonas | 56% | 5.3 | 168 |
| Biochar 3% + both microbes | 22% | 8.7 | 213 |
Yield is shown relative to untreated plants (our calculation), because the paper's yield unit is unclear. Disease is the paper's disease severity index.
- Dose mattered. Biochar worked best at 3–3.5% of soil weight. At 2% and at 4% the disease was roughly twice as severe.
- Combinations did not always help. Biochar with Pseudomonas alone had more disease than biochar alone, and biochar with Trichoderma alone was no better than biochar alone.
- The plants' own defences rose. In the best treatments, plants had more defence chemicals (phenols and proteins), and plants with more of them had less disease.
- In lab dishes, biochar with Trichoderma stopped almost all growth of the blight fungus.
In simple words: the right amount of biochar in the soil made brinjal plants much less sick from blight, and adding both friendly microbes gave the biggest harvest. But this happened in pots, with one variety and one season.
What this study does not tell us
- Pots, not fields: one variety, one season, one place, and an infection added by hand. Field results can differ.
- The biochar dose is large for a field. 3% of the soil's weight, mixed into the top 15 cm of a hectare, would be roughly 60 tonnes (our estimate), far more than most field studies use.
- Only one biochar was tested: an alkaline teak-wood biochar (pH 8.5). Biochar from rice husk or crop stalks can behave differently.
- The yield unit is unclear in the paper, so we compare yields with untreated plants rather than quote kilograms.
- The paper calls the three-way mix "synergistic", but biochar alone at 3–3.5% gave similar disease control; the mix stood out mainly for yield.
- No cost was measured, and a few treatment numbers in the paper's text do not match its tables; we used the tables.
The authors say pot and large-scale field trials are the next step. For now, this is good evidence that biochar and bio-agents deserve field testing against Phomopsis blight, not a ready field recipe.
How to manage Phomopsis blight today
- Start with clean seed. Use seed from healthy fruit and fields. Hot-water treatment of seed at 50°C for 30 minutes, or seed treatment with Trichoderma, is recommended against this disease.
- Raise a healthy nursery. Solarise nursery beds under clear polythene before sowing, add Trichoderma to the nursery soil, and transplant only healthy seedlings.
- Keep the field clean. Pick and destroy infected leaves and fruit, remove crop debris after harvest, and keep brinjal off the same land for a few seasons (TNAU advises a three-year rotation).
- Use registered bio-agents. Trichoderma and Pseudomonas fluorescens products are sold in India; choose ones with a CIB&RC registration number and follow the label.
- Try biochar on a small patch first. Mix it with compost or farmyard manure, and remember it is not a fertilizer. Ask your KVK about a sensible dose for your soil.
- Act early in humid weather. If the disease spreads, ask your KVK or agriculture officer which registered fungicide to use, and when.
What comes next
The next step is field trials with practical biochar doses, more varieties and seasons, and a check of cost against benefit. Dr. Mathur's work on microbial formulations is part of turning findings like these into products farmers can use.
NanoKheti does not sell biochar or the bio-agents tested here.
