Field pea (Pisum sativum var. arvense) is a vital cool-season legume crop that holds significant importance in ensuring food and nutritional security worldwide. Rich in protein, fiber and essential micronutrients, it plays a pivotal role in the diets of many populations, particularly in developing regions. Beyond its nutritional value, field pea also contributes substantially to sustainable agricultural practices, owing to its ability to fix atmospheric nitrogen through symbiotic associations with Rhizobium bacteria. This natural process enhances soil fertility and reduces dependency on synthetic nitrogen fertilizers, making field pea a key component in eco-friendly cropping systems. Despite these advantages, field pea cultivation faces a daunting challenge in the form of Fusarium wilt, a disease caused by the soil-inhabiting fungus Fusarium oxysporum f. sp. pisi. This pathogen has emerged as a major constraint to pea production across many parts of the world. The problem is particularly severe in regions such as the Bundelkhand area of India, where unfavourable agricultural practices like monocropping, poor crop rotation and declining soil health have intensified the disease burden (Kraft and Pfleger, 2001). Once the pathogen infects the plant, it colonizes the vascular xylem tissues, disrupting water and nutrient transport. This leads to the characteristic symptoms of wilting, leaf yellowing (chlorosis) and eventual plant death. The yield impact of Fusarium wilt is severe, ranging from about 30% in moderately resistant cultivars to as high as 95% in susceptible genotypes when disease pressure is high (Maheshwari et al., 1983). Management of Fusarium wilt traditionally relies on chemical fungicides, which are known for their broad-spectrum and rapid action. However, long-term use of chemical fungicides presents several significant issues. These include the risk of environmental contamination, negative effects on beneficial soil organisms, residual toxicity and the development of fungicide-resistant strains of the pathogen. As awareness grows regarding these risks, there is a noticeable shift in preference toward more sustainable and integrated disease management practices that reduce reliance on chemical inputs. Among the alternative strategies, the use of biological control agents, particularly Trichoderma species, has shown considerable promise. These beneficial fungi are known for their ability to suppress a variety of plant pathogens through multiple mechanisms, including mycoparasitism, where they directly attack and degrade the pathogen’s mycelium; competition for nutrients and space in the rhizosphere; and stimulation of plant defense mechanisms, often referred to as induced systemic resistance (Harman et al., 2004). Because of these multifaceted modes of action and their compatibility with sustainable agriculture, Trichoderma spp. are gaining increasing popularity as environmentally safe biocontrol agents. However, despite the potential of Trichoderma, a major bottleneck in their widespread adoption is the limited understanding of how these bio-agents interact with commonly used fungicides. In practical farming situations, especially in integrated pest and disease management programs, the concurrent use of bio-control agents and chemical fungicides is quite common. If the fungicide adversely affects the growth or survival of the bio-agent, the intended benefits of such integration may be lost. Hence, assessing the compatibility of bio-agents with fungicides is essential for ensuring their effective co-application and for formulating integrated disease management protocols that are both efficient and environmentally friendly. With these challenges in view, the present study was undertaken to explore a comprehensive approach to Fusarium wilt management in field pea. The investigation was structured around four primary objectives. Firstly, the study aimed to evaluate the antagonistic potential of six different Trichoderma isolates against F. oxysporum f. sp. pisi under laboratory conditions, to identify the most effective isolate for suppressing the pathogen. Secondly, seven commonly used fungicides were tested across various concentrations to determine their inhibitory effect on Fop, allowing for a comparative assessment of chemical control options. Thirdly, the study focused on determining the compatibility of the most effective Trichoderma isolate T. harzianum-3 (TH-3) with selected fungicides. This was crucial for evaluating whether these biological and chemical agents could be applied together without compromising each other’s efficacy. Lastly, to ensure the practical relevance of the findings, in-vivo experiments were conducted under net house conditions to validate the results obtained in the laboratory and assess the real-world effectiveness of integrated applications in disease suppression. Through this comprehensive framework, the study sought to bridge the gap between biological and chemical control methods, offering insights into a more balanced and sustainable approach to manage Fusarium wilt in field pea. The integration of compatible biological agents with selective fungicides could pave the way for effective disease control strategies that are not only economically viable but also environmentally responsible, thus supporting long-term agricultural productivity.

Isolation and identification of the pathogen
 
To obtain a pure culture of F. oxysporum f. sp. pisi infected root samples of field pea plants exhibiting typical wilt symptoms were collected from the research fields of Banda University of Agriculture and Technology (BUAT). The root tissues were cut into small pieces and subjected to surface sterilization using 1% sodium hypochlorite (NaOCl) solution for one minute. After thorough rinsing with sterile distilled water, the pieces were placed on potato dextrose agar (PDA) medium plates and incubated at 25±2°C. Fungal colonies that emerged were sub-cultured and examined under microscope at 40× magnifications. The pathogen was identified based on the morphology of its spores, including the presence of oval-shaped microconidia measuring approximately 3.1-6.2 µm and fusiform macroconidia ranging from 11.6-25.2 µm. To confirm pathogenicity, Koch’s postulates were completed by inoculating healthy field pea plants with the isolated fungus and re-isolating pathogen from symptomatic tissues of the infected plants.
 
Preparation and multiplication of bio-control agents
 
Six isolates of Trichoderma spp., namely T. harzianum-1 to T. harzianum-5 and T. viride-1, were obtained from the Department of Plant Pathology, BUAT. These isolates were maintained on PDA medium and stored at 25±2°C for routine use. For mass multiplication, each isolate was inoculated onto sterilized sorghum grains and incubated for 10 days at 25°C. The colonized grains served as inoculum for further studies, including in-vitro and in-vivo experiments.
 
Evaluation of antagonistic activity under in-vitro
 
The antagonistic potential of the six Trichoderma isolates against F. oxysporum f.sp pisi was evaluated using the dual culture technique. For this assay, 5 mm diameter mycelial discs of both fungicides and each Trichoderma isolate were placed on opposite sides of a PDA plate, approximately 4 cm apart. The plates were incubated at 25±2°C and the radial growth of the pathogen was measured after 7 days. The per cent inhibition of F. oxysporum f. sp. pisi growth was calculated using the formula:

 
Where,
I = Percent inhibition.
C = Growth test pathogen in control.
T = Growth of the pathogen in dual culture.
C = Radial growth of F. oxysporum f. sp. pisi in the control (without Trichoderma).
T = Growth of F. oxysporum f. sp. pisi in the presence of the antagonistic isolate.
 
Assessment of fungicide efficacy against F. oxysporum f. sp. pisi
 
The effectiveness of seven fungicides was tested using the poisoned food technique. Each fungicide was incorporated into PDA at concentrations of 10, 25, 50, 100 and 150 ppm. After the medium solidified, 5 mm diameter mycelial plugs of Fop were centrally placed on each plate. The plates were then incubated under standard conditions and the radial growth of the pathogen was measured after 7 days. This allowed for the evaluation of fungicide toxicity across a range of concentrations.
 
Compatibility test between TH-3 and fungicides
 
To examine the compatibility between the most effective Trichoderma isolate (T. harzianum-3, or TH-3) and selected fungicides, TH-3 was cultured on PDA plates amended with different fungicide concentrations (ranging from 10 to 150 ppm). The growth of TH-3 was compared with that on fungicide free control plates. The percentage of growth inhibition was calculated to determine the extent to which each fungicide affected the development of the TH-3. This compatibility study aimed to identify fungicides that could be used in conjunction with TH-3 without significantly inhibiting its growth, thereby facilitating integrated disease management strategies.

Antagonistic effect on pathogen
 
The investigation into the antagonistic potential of various Trichoderma isolates against F. oxysporum f. sp. pisi under laboratory conditions revealed significant variability in their efficacy. Among the six isolates tested, T. harzianum-3 (TH-3) demonstrated the highest antagonistic activity, achieving 66.09% inhibition of F. oxysporum f. sp. pisi mycelial growth, which was notably higher than that observed in other isolates. T. harzianum-4 and T. viride-1 followed with 61.57% and 59.93% inhibition, respectively. The inhibitory effects of all tested isolates are summarized in Table 1. Microscopic examination of the dual culture plates revealed clear indications of mycoparasitism by TH-3, including hyphal coiling and lysis of F. oxysporum f. sp. pisi hyphae, further confirming its strong antagonistic capabilities. These observations are supported visually in Plate 1, which presents micrographs showing hyphal interactions between TH-3 and F. oxysporum f. sp. pisi. The present findings are in agreement with earlier reports demonstrating the antagonistic potential of Trichoderma species against various species of F. oxysporum. Harman (2005) and Joshi and Sunkad (2025) described Trichoderma spp. as effective plant symbionts and biological control agents capable of suppressing soil-borne pathogens through multiple mechanisms. Similarly, Benitez et al., (2004) emphasized that antibiosis, competition and mycoparasitism are the principal mechanisms involved in pathogen suppression by Trichoderma. Chanu et al., (2024) also reported significant inhibition of F. oxysporum f. sp. pisi by Trichoderma isolates under laboratory conditions. The results of the present study further support the role of Trichoderma as an eco-friendly and sustainable alternative to sole chemical control.




 
Efficacy of fungicides
 
In evaluating the efficacy of different fungicides, Carbendazim 50% WP and Tebuconazole 50% + Trifloxystrobin 25% WG completely inhibited F. oxysporum f. sp. pisi growth at concentrations of 25 ppm and above. Even at the lower concentration i.e. 10 ppm, Carbendazim 50% WP exhibited substantial inhibitory activity (86.85%). In contrast, Azoxystrobin 23% SC demonstrated only limited suppression (26.85% inhibition at 150 ppm), suggesting low sensitivity of F. oxysporum f. sp. pisi to this fungicide. Detailed inhibition percentages for each fungicide at different concentrations are presented in Table 2 and images of plates and different inhibition percentage in Plate 2. The efficacy of fungicides against F. oxysporum f. sp. pisi in-vitro is reported by (Sagar et al., 2021; Chanu et al., 2019; Bhagat et al., 2025; Verma and Dohroo, 2002).




 
Compatibility of bio-agents and fungicides
 
To determine the potential for combining bio-agents with fungicides in an integrated management strategy, the compatibility of TH-3 with selected fungicides was examined. The isolate maintained substantial viability when exposed to Azoxystrobin 23% SC, showing only 33.88% growth inhibition at 150 ppm concentration and exhibited moderate tolerance to Carboxin 17.5% + Thiram 17.5% FF with 73.70% inhibition. However, exposure to Carbendazim 50% WP led to complete inhibition of TH-3 at concentrations as low as 25 ppm, indicating incompatibility. A summary of TH-3 growth on fungicide-amended PDA is provided in Table 3, evaluations of different fungicides against TH-3 are shown in Plate 3. This finding is supported by earlier researchers Elshahawya et al., (2016) and Kumar et al., (2021).




       
The integrated application of TH-3 with Provax under in-vivo (net house) conditions significantly reduced Fusarium wilt incidence, achieving a 68.33% reduction compared to untreated controls. This was superior to the 60% reduction observed with Carbendazim treatment alone. Collectively, these findings affirm that TH-3 has a robust antagonistic effect against F. oxysporum f. sp. pisi, both independently and in combination with select fungicides. The strong inhibitory mechanisms such as enzyme production, direct parasitism and secondary metabolite secretion likely contribute to its superior performance (Ramezani, 2010). While Bavistin remains a highly effective fungicide against F. oxysporum f. sp. pisi incompatibility with Trichoderma suggests that its use should be restricted or applied with a time gap when used alongside biological agents. On the other hand, Amistar and Provax, though less potent against F. oxysporum f. sp. pisi alone, often compatibility with TH-3, making them suitable components for integrated strategies. The efficacy of Trichoderma viride and carboxin 75WP (vitavax) were evaluated as seed dressing and soil application individually and in combinations under field experiments during Kharif 2012-2013 for the management of Root rot/wilt complex and white rot of garden pea by Kumar (2015).

In light of increasing concerns over fungicide resistance, especially with the continued use of single site inhibitors like Carbendazim (Pancholi et al., 2022; Dinkwar et al., 2023), combining compatible bio-agents such as TH-3 with systemic fungicides could help delay resistance and improve long term disease control in field pea cultivation. Proper timing and sequencing of applications such as soil treatment with TH-3 before sowing followed by foliar application of compatible fungicides during critical growth stages can enhance efficacy while promoting sustainability in wilt management practices.
       
The present investigation aimed to assess the efficacy of selected bio-agents and fungicides against F. oxysporum f. sp. pisi, the causative agent of Fusarium wilt in field pea, through both in vitro and in vivo approaches. Among six isolates of Trichoderma evaluated, T. harzianum-3 (TH-3) demonstrated the strongest antagonistic effect, reducing the mycelial growth of F. oxysporum f. sp. pisi by 66.09%, followed by T. harzianum-4 (61.57%) and T. viride-1 (59.93%). The lowest inhibition was recorded with T. harzianum-5 (44.28%). These observations align with earlier research by Waghmare et al., (2008) and Ramezani (2010), who documented the effectiveness of Trichoderma species against various formae speciales of F. oxysporum. The biocontrol activity of TH-3 is likely due to mechanisms such as hyphal parasitism, production of antifungal compounds and competitive exclusion (Harman et al., 2004; Benitez et al., 2004). Similar findings were reported by Abdulle et al., (2022) for T. harzianum in chickpea.
       
Chemical control trials revealed that Carbendazim 50% WP and Tebuconazole + Trifloxystrobin completely inhibited F. oxysporum f. sp. pisi, except Nativo at 10 ppm, which still showed 86.85% inhibition. These results corroborate findings by Kumari et al., (2021) and Kavya and Tewri (2022), who highlighted the efficacy of Carbendazim and Tebuconazole based fungicides against related F. oxysporum strains. Vitavax Power and Thiram were moderately effective, whereas Amistar (Azoxystrobin) was least effective, showing only 26.85% inhibition at 150 ppm.
       
Compatibility studies using the poisoned food technique indicated that Amistar was most compatible with TH-3, with only 33.88% inhibition at 150 ppm, followed by Provax. In contrast, Bavistin and Nativo completely suppressed TH-3 even at 25 ppm, rendering them unsuitable for integrated use. These findings support results by Dinkwar et al., (2023), who reported varying compatibility of Trichoderma spp. with different fungicides.

In net house trials, the combined use of TH-3 and Provax resulted in a 68.33% reduction in disease incidence, indicating a synergistic effect. This combination balances systemic fungicidal action with localized biocontrol and offers a sustainable approach to managing Fusarium wilt. Strategic integration of bio-agents and compatible fungicides, with attention to application timing, can enhance disease control efficacy while promoting eco-friendly farming (Pancholi et al., 2022).
 
Efficacy of integrated treatments on germination and incidence of Fusarium wilt of pea
 
The result showed that all the treatment were effective for seed germination and also reduce the incidence of wilt over control (Table 4). The treatment 3 provide the best germination (100 %) and treatment 6 had the highest disease reduction (69.23 %) and second highest germination percent and immediately next to it was treatment 3 (ST with carbendazim @2g/kg) which showed 61.55 % disease reduction followed by treatment 5 (Soil application with TH-3 @10g/kg + Amistar @1 ml/kg ST) which exhibited 53.84 percent disease reduction. Treatment 4 (ST with vitavax power @1g/kg) showed 38.47 % disease reduction. The least effective treatment was noted treatment 2 (ST with TH-3 @6g/kg) which exhibited 15.39 % in wilt reduction. Similar studies were also reported by Parmar and Gohel (2024) and Nain et al., (2024).

This study highlights the effectiveness of T. harzianum-3 and combination fungicides like Carbendazim 50% WP and Tebuconazole + Trifloxystrobin in managing Fusarium wilt in field pea. The strong antagonistic response of TH-3 and complete pathogen suppression by certain fungicides demonstrate their potential as key components of an integrated disease management strategy. Compatibility data further supports their combined use, allowing for more efficient and sustainable control measures. Moving forward, field-level validation, exploration of resistance mechanisms and assessment of economic feasibility particularly for small-scale farmers will be important to support practical and widespread adoption.

We acknowledged the Department of Plant Pathology, College of Agriculture, Banda University of Agriculture and Technology, Banda Uttar Pradesh for provide the necessary support during the investigation.

On behalf of all authors, the corresponding authors declare the following interest: The authors declare no conflict of interest.