Evaluation of eco-friendly and sustainable control measures against Turcicum leaf blight disease in maize cultivation

Introduction

Maize (Zea mays L.) is one of the most important cereal crops cultivated worldwide and ranks third after wheat and rice in terms of area and production. Owing to its high nutritional value and versatility, maize serves as a staple food for millions of people and is extensively utilized as animal feed and as a raw material in several industrial sectors, including starch, biofuel, pharmaceutical, and food-processing industries. [1][2][3][4][5] In India, maize is cultivated across diverse agro-climatic regions and contributes significantly to agricultural income and food security. However, achieving optimum productivity remains challenging because of several biotic and abiotic constraints, among which foliar diseases constitute a major limiting factor. Turcicum leaf blight (TLB), also known as northern corn leaf blight, caused by Exserohilum Turcicum (Pass.) Leonard and Suggs, is one of the most destructive diseases affecting maize production worldwide. The disease is prevalent in tropical, subtropical, and temperate regions, particularly under conditions of moderate temperature, high relative humidity, prolonged leaf wetness, and frequent rainfall [6][7][8][9][10][11][12] . Characteristic symptoms include elongated, elliptical, greyish-green lesions that gradually enlarge and turn tan or necrotic, ultimately leading to extensive leaf blighting. Severe infection causes premature senescence of leaves, reduced photosynthetic efficiency, poor grain filling, and significant yield losses, which may range from 20 to 70% depending on cultivar susceptibility, environmental conditions, and disease severity.

The pathogen survives in infected crop residues and spreads through wind-borne conidia, making disease management difficult under favorable environmental conditions. Conventional control strategies rely heavily on the use of synthetic fungicides and resistant cultivars. Although fungicides provide effective and rapid disease suppression, indiscriminate and prolonged application of chemical pesticides has raised serious concerns regarding environmental pollution, residual toxicity, increased production costs, development of fungicide-resistant pathogen populations, and adverse effects on beneficial microorganisms and ecosystem health. Furthermore, growing awareness regarding food safety and sustainable agricultural practices has necessitated the development of environmentally benign alternatives for disease management. Eco-friendly disease management approaches involving biological control agents, plant-derived botanicals, and organic amendments have emerged as promising alternatives to conventional fungicides. Beneficial microorganisms such as Trichoderma harzianum, Trichoderma viride, Pseudomonas fluorescens, and Bacillus subtilis have demonstrated significant antagonistic activity against several phytopathogenic fungi through mechanisms including mycoparasitism, competition, antibiosis, and induction of systemic resistance. Similarly, botanical extracts obtained from plants such as neem (Azadirachta indica), garlic (Allium sativum), tulsi (Ocimum sanctum), and ginger (Zingiber officinale) contain diverse bioactive compounds possessing antifungal, antimicrobial, and antioxidant properties that can effectively suppress pathogen development while minimizing ecological risks [13][14][15] . Integrated utilization of bioagents and botanicals offers several advantages, including reduced dependence on chemical pesticides, lower environmental contamination, improved soil microbial diversity, enhanced plant growth, and sustainable crop production. Such approaches are consistent with the principles of integrated disease management (IDM) and sustainable agriculture, which emphasize ecological balance and long-term productivity. Moreover, increasing consumer demand for residue-free agricultural products has further accelerated interest in biological and plant-based disease management strategies [16] . Despite considerable progress in the development of eco-friendly technologies, information regarding the comparative efficacy of biological control agents and botanical extracts against Turcicum leaf blight under field conditions remains limited. Therefore, there is a need to evaluate sustainable alternatives capable of effectively managing the disease while ensuring environmental safety and economic viability [17][18][19][20][21] . In view of these considerations, the present investigation was undertaken to evaluate the effectiveness of selected eco-friendly and sustainable control measures against Turcicum leaf blight of maize and to assess their influence on disease severity, plant growth, and yield attributes under field conditions. The findings of this study may contribute to the development of integrated and environmentally sound disease management strategies for sustainable maize cultivation. Therefore, the present study was undertaken to evaluate the efficacy of biological and botanical treatments against Turcicum leaf blight and their effects on growth and yield of maize under field conditions.

Materials and Methods

Experimental Site and Climatic Conditions

The present investigation was conducted during the Kharif season of 2024-2025 at the Experimental Farm of the KVK Jammu Experimental Farm, located under subtropical climatic conditions. The experimental field was characterized by sandy loam soil with good drainage and a pH ranging from 6.5 to 7.2. The average temperature during the crop-growing period ranged from 22 to 32 °C, with relative humidity varying between 70 and 90%, conditions favorable for the development of Turcicum leaf blight. Standard agronomic practices recommended for maize cultivation were followed throughout the experiment.

Plant Material and Pathogen

A susceptible maize cultivar was used for the study to ensure uniform disease development. Turcicum leaf blight was caused by Exserohilum Turcicum (Pass.) Leonard and Suggs. Diseased leaf samples exhibiting typical symptoms were collected from naturally infected maize fields. The pathogen was isolated on potato dextrose agar (PDA) medium and purified by single-spore isolation. Identification of the pathogen was performed based on cultural and morphological characteristics.

Treatments and Experimental Design

The experiment was laid out in a Randomized Block Design (RBD) with three replications. Each treatment plot measured 4 × 3 m with recommended spacing of 60 × 20 cm. Eight treatments comprising biological control agents and botanical extracts were evaluated along with untreated control.

Treatments

Preparation of Botanical Extracts

Fresh neem seeds and garlic cloves were washed thoroughly and crushed separately using distilled water. The extracts were filtered through muslin cloth and diluted to obtain desired concentrations. Fresh extracts were prepared before each spray to maintain efficacy. Foliar applications were carried out at 45 and 60 days after sowing.

Disease Assessment

Disease severity was recorded at 75 and 90 days after sowing using a 1-9 scale based on lesion development and percentage leaf area infected. Percent Disease Index (PDI) was calculated using the formula: PDI = (Sum of numerical ratings × 100)/(Total number of leaves observed × Maximum disease grade) Disease incidence was determined by counting infected plants and expressing them as percentage of total plants examined.

Growth and Yield Parameters

Observations were recorded on:  Plant height (cm)  Number of leaves plant⁻¹  Leaf area index  Cob length (cm)  Number of grains cob⁻¹  1000-grain weight (g)  Grain yield (t ha⁻¹)

Statistical Analysis

Experimental data were subjected to analysis of variance (ANOVA) appropriate for Randomized Block Design. Treatment means were compared using Duncan's Multiple Range Test (DMRT) at a significance level of P≤0.05. Statistical analysis was performed using SPSS version 25.0.

Results

Effect of Eco-Friendly Treatments on Disease Severity

Significant differences among treatments were observed with respect to disease incidence and severity. Among the various treatments, T 5 (Trichoderma harzianum + neem seed kernel extract) recorded the lowest disease severity (18.6%) and disease incidence (22.4%), followed by T 6 (Pseudomonas fluorescens + garlic extract), which exhibited disease severity of 23.7%. The untreated control recorded the highest disease severity (62.8%) and incidence (71.4%). The combined application of biological control agents and botanical extracts proved more effective than individual treatments, indicating synergistic interactions between antagonistic microorganisms and plant-derived antifungal compounds [22][23][24][25] .

Effect on Plant Growth Parameters

Eco-friendly treatments significantly influenced plant growth. Maximum plant height (228.6 cm), number of leaves per plant (14.2), and leaf area index (4.5) were observed in T 5 . Enhanced growth might be attributed to improved nutrient uptake and suppression of pathogen activity by beneficial microorganisms [26][27][28][29][30] . Plants treated with Trichoderma harzianum showed vigorous growth and greener foliage compared with untreated plants, indicating induction of plant growth-promoting effects.

Effect on Yield Attributes

Treatments significantly affected yield components. The highest cob length (19.8 cm), grains per cob (514), and 1000-grain weight (312 g) were recorded in T 5 , followed by T 6 and T 8 . Untreated plants produced shorter cobs with fewer grains and lower grain weight. Reduction in disease severity contributed to enhanced photosynthetic activity and improved grain filling, thereby increasing productivity.

Effect on Grain Yield

Maximum grain yield (7.62 t ha⁻¹) was recorded in T 5 , followed by T 6 (7.14 t ha⁻¹) and T 8 (7.30 t ha⁻¹). The untreated control recorded the lowest yield (4.86 t ha⁻¹). Integrated biological and botanical treatments resulted in 56-60% higher yield over control. These results indicate that eco-friendly management approaches can effectively replace or supplement synthetic fungicides in maize cultivation.

Discussion

Turcicum leaf blight is among the most destructive foliar diseases of maize and remains a major challenge in achieving sustainable crop productivity. The present investigation demonstrated that biological control agents and botanical extracts significantly reduced disease severity and improved plant growth and yield. Among the tested treatments, the combined application of Trichoderma harzianum and neem seed kernel extract proved superior in suppressing disease development. The effectiveness of Trichoderma species may be attributed to multiple mechanisms, including competition for nutrients, mycoparasitism, production of antifungal metabolites, and induction of systemic resistance in host plants [26][27][28][29][30][31][32][33][34] . Similarly, neem seed extracts contain azadirachtin, nimbin, and other bioactive compounds that possess potent antifungal properties. The synergistic interaction between microbial antagonists and plant-derived compounds resulted in greater suppression of Exserohilum Turcicum compared with individual applications. Enhanced plant growth and yield observed in treated plants may also be associated with the plant growth-promoting activities of beneficial microorganisms. Trichoderma and Pseudomonas fluorescens are known to improve nutrient availability, produce phytohormones, and stimulate root development, thereby increasing crop vigor and tolerance against pathogens. Similar findings have been reported by several investigators who demonstrated significant reductions in foliar diseases of maize through integrated biological management approaches. The results obtained in the present study support the growing emphasis on sustainable agriculture and integrated disease management. Excessive dependence on synthetic fungicides poses risks of environmental contamination, pathogen resistance, and harmful effects on beneficial organisms. In contrast, eco-friendly alternatives provide effective disease suppression while maintaining ecological balance and soil health [35][36][37][38][39][40][41][42] . Therefore, integration of bioagents and botanicals can be considered a promising strategy for sustainable management of Turcicum leaf blight in maize. Adoption of these environmentally benign approaches can contribute to reduced chemical inputs, improved crop productivity, and enhanced food security while promoting sustainable agricultural practices [43][44][45][46] .

Conclusion

The present investigation demonstrated that eco-friendly and sustainable management strategies can effectively suppress Turcicum leaf blight caused by Exserohilum Turcicum in maize while improving crop growth and productivity. Among the various treatments evaluated, the combined application of Trichoderma harzianum and neem seed kernel extract proved to be the most effective, resulting in the lowest disease incidence and severity and the highest grain yield. Biological control agents and botanical formulations not only reduced pathogen development but also promoted plant growth and enhanced yield attributes. The findings of this study emphasize the potential of integrating bioagents and plant-based products as environmentally benign alternatives to synthetic fungicides. Such approaches contribute to reduced chemical inputs, preservation of soil microbial diversity, and maintenance of ecological balance, thereby supporting the principles of sustainable agriculture and integrated disease management. Furthermore, the use of these eco-friendly treatments can minimize the risks associated with fungicide resistance and pesticide residues, while ensuring safer and more sustainable maize production. Overall, the integration of Trichoderma harzianum with neem seed kernel extract emerged as a promising strategy for the management of Turcicum leaf blight and may be recommended as a component of integrated disease management programs. Further investigations involving multi-location trials, optimization of application schedules, and evaluation under diverse agro-climatic conditions are warranted to validate their long-term efficacy and facilitate large-scale adoption by farmers. The adoption of such sustainable approaches will contribute significantly to enhancing maize productivity, environmental conservation, and global food security.

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