Trichoderma or Carbendazim? What Two Indian Field Trials Actually Show for Chickpea and Pigeonpea Wilt

Executive Summary

For a pulse grower in Madhya Pradesh, Maharashtra or Bihar, wilt is not a spray decision. By the time a chickpea plant wilts in the field or a pigeonpea shows the purple band creeping up its stem, the pathogen is inside the vascular system and nothing applied to the canopy will reach it. The only moment of real leverage over Fusarium oxysporum f. sp. ciceris and Fusarium udum is the moment the seed is treated.

The usual framing of that decision — Trichoderma versus carbendazim — turns out to be the wrong question. Two recent Indian field studies, one on chickpea at ICAR-IARI New Delhi and one on pigeonpea at Dr. Rajendra Prasad Central Agricultural University, Pusa, both tested bio-agent seed treatment against carbendazim in wilt-sick fields, and reached visibly different conclusions. Read together they show that what matters is not biology versus chemistry but which strain is used and how it is delivered and kept alive until sowing.

Two Pathogens, One Point of Intervention

Chickpea (Cicer arietinum) anchors India's rabi pulse area. Pradhan and co-workers, writing in Frontiers in Plant Science in 2022, summarise the national position as roughly 112 lakh hectares producing about 116.20 lakh tonnes at 1,036 kg per hectare in 2020–21 — some 38 per cent of India's pulse area and around half of total pulse production. Pigeonpea (Cajanus cajan) is smaller but strategically critical; Reddy and colleagues at RPCAU cite about 45 lakh hectares and 42 lakh tonnes annually, with India accounting for close to 90 per cent of world acreage and production.

F. oxysporum f. sp. ciceris enters chickpea through the roots and the emerging germ tube. F. udum enters pigeonpea through root tips and disrupts water and mineral transport in the vascular bundles. What makes both intractable is persistence: the RPCAU team note that prolonged survival of the fungus in soil and plant debris defeats conventional management such as crop rotation and flooding.

For chickpea wilt an average annual loss of 10–15 per cent is commonly reported, reaching up to 100 per cent under severe conditions. Pigeonpea losses are staged by timing of infection — up to 100 per cent at pre-podding, around 67 per cent at pre-harvest, about 30 per cent at maturity.

What Carbendazim Does, and Where It Stops

Carbendazim is the benzimidazole Indian pulse growers have leaned on for decades, and the Frontiers authors describe it plainly as the most widely used and recommended fungicide for wilt management in legumes. As a seed dressing it protects seed and seedling through the germination window, when the germ tube is most exposed.

Its limits are structural rather than chemical. A dressing protects a zone around the seed for a finite period, but wilt pressure is not confined to that window. In the IARI chickpea trial described below, wilt incidence was still climbing at 60 days after sowing; in pigeonpea the RPCAU group record wilt symptoms at both seedling and adult stages. They also put the economics from the other direction — fungicide application is helpful up to seed treatment but neither feasible nor economical once the crop is established, precisely because the pathogen is soil-borne — and flag the standing risk of resistance developing to commonly used fungicides.

A living antagonist, in principle, answers that: it colonises the root as the root grows, so it is still present when the second wave arrives. Whether that principle survives contact with an Indian field is the question.

The Chickpea Evidence: ICAR-IARI, Rabi 2021–22

Pradhan and colleagues from the Divisions of Agricultural Chemicals, Plant Pathology and Genetics at ICAR-Indian Agricultural Research Institute, New Delhi, ran a field experiment at the institute farm in rabi 2021–22. The site was a Fusarium wilt sick field carrying 2 × 10⁷ cfu of the pathogen per gram of soil at sowing; the design was a randomised block, nine treatments, three replications, on the moderately susceptible variety Pusa-372 at 30 × 10 cm spacing and a seed rate of 60 kg per hectare.

Five Trichoderma viride strains from the Indian Type Culture Collection were screened first, with ITCC 7764 strongest. It was formulated as a dustable seed-treatment powder on a biopolymer, xerogel, neem leaf powder and clay base, then compared against carbendazim 50% WP and a conventional talc-based Trichoderma formulation.

How the disease curve separates

The instructive feature is the slope, not any single reading. Untreated wilt climbed from 28.33 to 50.00 per cent between 30 and 60 DAS. Under carbendazim it climbed from 19.17 to 30.00 — a real reduction, but the same upward trajectory, consistent with a protectant whose influence is fading. Under the biopolymer-based powder it moved only from 8.33 to 12.50. The authors report that the developed formulations suppressed disease significantly more than both carbendazim and the talc formulation at each time point.

The yield result deserves a careful reading

Yield followed the same ranking: 21.29 q/ha for the seed-treatment powder against 19.83 for carbendazim, 18.16 for talc and 15.16 untreated. But the statistical grouping matters. In the published table the best biological treatment and carbendazim share a letter group under Duncan's test at p<0.05, meaning the yield difference between them was not statistically separable, even though the disease-suppression difference was. That nuance is the honest headline: on one season at one site the superior formulation beat the fungicide convincingly on disease and matched it on yield. Claiming a proven yield advantage reads more into the table than it says.

The Pigeonpea Evidence: Four Seasons at RPCAU Pusa

The pigeonpea picture is less flattering to biology, and more useful for it. Reddy, Kumar, Sahni and colleagues at the Department of Plant Pathology, RPCAU Pusa, Bihar, published in Scientific Reports in 2024 a four-season sick-plot evaluation — kharif and rabi of 2021–22 and of 2022–23 — on the wilt-susceptible cultivar ICP 2376, having first screened 100 endophytic bacteria, 100 rhizosphere bacteria and three Trichoderma species against a virulent F. udum isolate.

Three things stand out. The best biological treatments did not defeat carbendazim here; they drew roughly level with it. Two of the three Trichoderma entries did substantially worse than the fungicide — around 53 per cent incidence against carbendazim's 36.5. And the AMMI analysis attributed 95.08 per cent of the total sum of squares to treatment effects, only 0.24 per cent to environment. Across four seasons the ranking held: the choice of agent, not the weather, decided the outcome.

Reading the Two Trials Together

Set side by side, the two studies do not contradict each other. They isolate different variables.

The genus is not the product

The clearest lesson comes from Pusa: T. harzianum returned 35.41 per cent incidence while T. asperellum returned 52.91 and an unidentified Trichoderma sp. 53.33 — same plots, same seasons, same pathogen. A product labelled "Trichoderma" tells a buyer almost nothing. At IARI the same principle showed at screening, where five T. viride strains spread across a 15-percentage-point range of mycelial inhibition before one was selected.

Delivery decides as much as the organism

The IARI trial carried an internal control easy to overlook. The talc-based Trichoderma formulation, representing the conventional Indian product format, finished at 32.50 per cent wilt at 60 DAS — marginally worse than carbendazim's 30.00 — while the same genus delivered through a biopolymer-and-xerogel powder finished at 12.50. The authors are explicit about why conventional wettable powders struggle: poor cfu load in storage, poor coating efficacy of dry powders, dust hazards. They also note that Trichoderma performance tracks moisture availability in the zone of application.

Duration of protection sets the ceiling

The chickpea data show biology holding a shallow disease curve to 60 DAS where the chemical curve kept rising. The pigeonpea data, a season mean on a long-duration crop, show a much narrower gap. No seed-applied treatment can hold an entire season of pressure alone: seed treatment is the foundation of pulse wilt management, not the whole of it.

The Dry Root Rot Complication

Chickpea growers in central and southern India increasingly face a second soil-borne problem that behaves differently. Dry root rot, caused by Macrophomina phaseolina (long referred to in Indian literature as Rhizoctonia bataticola), has been described in the peer-reviewed literature as an emerging threat to Indian chickpea production, with rising average temperature and erratic rainfall expected to worsen it. Controlled-environment work in Frontiers in Plant Science in 2021 found that high temperature around 35 °C combined with low soil moisture elicited the highest disease susceptibility in chickpea.

That matters for strategy because dry root rot expresses late, under terminal heat and moisture stress — the conditions at the tail of a central Indian rabi season, and exactly when a seed-applied protectant chemical is long spent. An agent that colonises and persists on the root has at least a mechanistic case for relevance at that stage; a protectant dressing does not.

Shelf Life and the CIB&RC Quality Standard

Any discussion of biological seed treatment in India has to confront a regulatory number. As the Frontiers authors record, the Central Insecticides Board and Registration Committee requires that an authentic biocontrol formulation of Trichoderma spp. carry 2 × 10⁶ cfu per gram of formulation at the time of its application in the field. The same source notes that wettable powder of T. viride (1% WP) is recommended in India for the management of chickpea wilt.

The operative phrase is at the time of application, not at the time of manufacture. Between a fermenter in one state and a sowing window in another sit transport, a distributor's shelf and a village godown through an Indian summer. A formulation that meets the standard when packed and fails it when sown is, functionally, untreated seed sold at a premium — the most plausible explanation for the gap between controlled-trial results and the inconsistent field performance growers report. That is a formulation and supply-chain problem, not a microbiology one.

Carrier Chemistry: What the Th4d Biopolymer Work Adds

Work published in ACS Omega in 2025 by Malavathu, Godbole, Singh, Chandrika and Prasad addresses that problem directly. The group entrapped Trichoderma harzianum Th4d spores — the strain that is the active agent in Seed Primer — within cross-linked porous biopolymer matrices designed for slow, sustained release, and report that the formulation retained spore viability for six months at 31 and 40 °C while improving both surface and endophytic root colonisation.

Two points of discipline are required. That study's efficacy work was on soybean and castor, not pulses: the CP-2 + Th4d seed treatment raised germination to 73.3 per cent in soybean and 96.6 per cent in castor, with Macrophomina root rot in soybean reduced to 23.3 per cent and Fusarium wilt in castor to 20 per cent. Those are not chickpea or pigeonpea results. What the work establishes is transferable in principle rather than in number — the thermal-stability problem that undermines talc formulations in Indian storage has a demonstrated answer in carrier chemistry. Validating it on pulses under Indian wilt-sick conditions still needs doing.

Compatibility and the Order of Operations

A pulse seed in India rarely receives one thing. It may receive a fungicide, an insecticide, a bio-agent and a Rhizobium or Mesorhizobium inoculant, and the order and spacing of those applications determine whether the last one survives.

The obvious conflict is chemical against biological. Carbendazim is a broad-spectrum fungicide; Trichoderma is a fungus. Loading both onto the same seed at once works against itself, and the IARI authors close their paper by calling specifically for further research on the compatibility of their formulations with other agrochemicals in order to build an integrated disease management schedule for chickpea. On their own account the question is unresolved — a reason to separate the two rather than assume the combination is safe.

The rhizobial side is more encouraging. Work in the Indian Journal of Microbiology in 2017 developed a Trichoderma viride–Mesorhizobium ciceri biofilmed inoculant for chickpea, reporting a 13–21 per cent increase in seed germination and a 10–11 per cent enhancement in antifungal activity against F. oxysporum f. sp. ciceri over M. ciceri alone. The fungal antagonist and the nitrogen-fixing symbiont are not natural enemies; they can be co-formulated. It is the benzimidazole that forces the choice.

What This Means for Seed Companies and Growers

For a seed company treating pulse seed before packaging, the evidence points to four obligations.

• Declare the strain, not the genus. A culture-collection accession number is the minimum; the Pusa data show a nearly 18-percentage-point spread between Trichoderma species in the same plots.
• Specify cfu at point of sowing. The CIB&RC threshold of 2 × 10⁶ cfu per gram applies at application. A specification that only holds at manufacture is not a specification.
• Treat the carrier as part of the product. Talc and biopolymer carriers delivering a comparable organism produced 32.50 and 12.50 per cent wilt in the same IARI field. The carrier is not packaging.
• Do not stack a benzimidazole and a live fungal antagonist on the same seed. Choose one pathway, or separate them deliberately and with evidence.

For the grower the guidance is narrower. Wilt is decided before sowing. Resistant or tolerant varieties remain the first line where they exist for the local race pressure — though the Pusa authors note open questions about the durability of field resistance to F. udum and about location-specific isolates. Seed treatment is the second line, and cheap relative to everything else in the season. What it is not is a rescue: once vascular discolouration is visible, no treatment recovers that plant.

Economics, Stated Plainly

It is tempting to convert these trials into rupees per hectare. The honest position is that neither study published a cost-benefit analysis, and inventing one would be worse than leaving it out. What can be stated is the physical arithmetic such a calculation would rest on.

In the IARI chickpea trial the seed rate was 60 kg per hectare, and the gap between untreated and best-treated plots was 21.29 against 15.16 q/ha — 6.13 quintals. Against carbendazim the gap narrows to 1.46 q/ha and, as noted, is not statistically separable. Seed treatment acts on sixty kilograms of input to influence an output measured in tonnes; that asymmetry, rather than any particular benefit-cost ratio, is why seed treatment survives scrutiny in Indian pulse budgets. The real question is not biological against chemical on headline price, but whether the biological pathway is delivered well enough to realise the suppression the trials show — a treatment that has lost viability in storage costs the same as one that has not, and delivers the outcome of untreated seed.

Conclusion

Two Indian field studies, two pulses, two states, both under wilt-sick conditions, converge on an unglamorous conclusion. At ICAR-IARI a well-chosen Trichoderma viride strain in an engineered carrier cut chickpea wilt to 12.50 per cent at 60 DAS where carbendazim left 30.00 per cent — while matching, not beating, the fungicide on yield. At RPCAU Pusa, over four seasons, the best biological seed treatments merely drew level with carbendazim on pigeonpea, and two Trichoderma isolates were markedly worse than it.

The variable explaining both outcomes is not biology against chemistry. It is whether a specific, screened strain reaches the soil alive, in sufficient numbers, in a carrier that keeps it that way. The question for Indian pulse belts is therefore not whether Trichoderma can control wilt — it demonstrably can — but whether the seed supply chain can deliver a defined strain at a defined cfu count to a field in Vidarbha or Bundelkhand in May. That is an engineering and quality-assurance problem, and it is the one worth solving.

References and Sources

• Pradhan, P. C., Mukhopadhyay, A., Kumar, R., Kundu, A., Patanjali, N., Dutta, A., Kamil, D., Bag, T. K., Aggarwal, R., Bharadwaj, C., Singh, P. K. & Singh, A. (2022). Performance appraisal of Trichoderma viride based novel tablet and powder formulations for management of Fusarium wilt disease in chickpea. Frontiers in Plant Science, 13. doi:10.3389/fpls.2022.990392 — ICAR-IARI, New Delhi; rabi 2021–22 wilt-sick field trial, variety Pusa-372.
• Reddy, B. D., Kumar, B., Sahni, S., Yashaswini, G., Karthik, S., Sai Reddy, M. S., Kumar, R., Mukherjee, U. & Sai Krishna, K. (2024). Harnessing the power of native biocontrol agents against wilt disease of Pigeonpea incited by Fusarium udum. Scientific Reports, 14, 12500. doi:10.1038/s41598-024-60039-0 — RPCAU Pusa, Bihar; four-season sick-plot evaluation, cultivar ICP 2376.
• Malavathu, K., Godbole, V., Singh, A., Chandrika, K. S. V. P. & Prasad, R. D. (2025). Porous Biopolymer Matrices: Advanced Seed Delivery Platforms for Beneficial Microbes to Combat Soilborne Diseases. ACS Omega. doi:10.1021/acsomega.5c01710 — Th4d in cross-linked biopolymer matrices; efficacy data on soybean and castor.
• Temperature and Soil Moisture Stress Modulate the Host Defense Response in Chickpea During Dry Root Rot Incidence (2021). Frontiers in Plant Science, 12, 653265. doi:10.3389/fpls.2021.653265
• A sick plot-based protocol for dry root rot disease assessment in field-grown chickpea plants (2021). Applications in Plant Sciences, 9. doi:10.1002/aps3.11445 — Macrophomina phaseolina, formerly Rhizoctonia bataticola.
• Development of Mesorhizobium ciceri-Based Biofilms and Analyses of Their Antifungal and Plant Growth Promoting Activity in Chickpea Challenged by Fusarium Wilt (2017). Indian Journal of Microbiology. doi:10.1007/s12088-016-0610-8
• Sunkad, G., Deepa, H., Shruthi, T. H. & Singh, D. (2019). Chickpea wilt: status, diagnostics and management. Indian Phytopathology, 72(4), 619–627. doi:10.1007/s42360-019-00154-5
• Venkataramanamma, K., Bhaskara Reddy, B. V., Jayalakshmi, R. S., Jayalakshmi, V. & Hari Prasad, K. V. (2023). Integrated disease management of Fusarium wilt (Fusarium oxysporum f. sp. ciceris) of chickpea. Indian Phytopathology, 76, 497–509. doi:10.1007/s42360-023-00625-w
• Central Insecticides Board and Registration Committee (CIB&RC), Government of India — minimum cfu specification for Trichoderma spp. biocontrol formulations and registration of T. viride 1% WP for chickpea wilt, as cited in Pradhan et al. (2022).

Figures in this article are reproduced as published by the cited institutions. Where a value could not be verified against a published source it has been described qualitatively rather than estimated.