Management of leaf curl virus disease of tomato (Solanum lycopersicon L.)

Introduction

The tomato (Solanum lycopersicon L.) is a highly significant commercial vegetable crop globally and in India, ranking second only to the potato in total production (Anonymous, 2025) [1] . Its flexibility, yield high potential and outstanding nutritional profile which includes vital antioxidants like lycopene, vitamin C and vitamin A make it highly prized (Sain and Chadha, 2012; Govindappa et al., 2013; Shelat et al., 2014). Tomato output is significantly hampered by a number of biotic stresses, especially viral infections, despite its extensive cultivation and economic significance (Saikia & Muniyappa, 1989). The most serious and damaging viral infection affecting tomatoes in India is known to be the tomato leaf curl virus (ToLCV) (Chakraborty, 2008; Jyothsna et al., 2013; Ranjan et al., 2013). This single-stranded DNA virus, which is a member of the Geminiviridae family, causes crippling symptoms such upward leaf curling, severe plant stunting, yellowing and blossom abortion. As a result, crop output is drastically reduced (Gafni, 2003; Crescenzi et al., 2004; Pandey et al., 2009). The whitefly, or Bemisia tabaci, is a highly effective insect vector that spreads the disease (Muniyappa and Veeresh, 1984; Uchibori et al., 2013). Managing viral infections spread by insects is a major concern since whiteflies are small, highly mobile, and challenging to keep out of agricultural regions (Mason et al., 2000). Furthermore, because resistance is a complicated genetic trait, total genetic resistance in tomato cultivars has not yet been attained (Maruthi et al., 2003; Singh, 2014). As a result, an integrated pest management (IPM) strategy that makes use of cultural, physical, biological, and chemical techniques is necessary for effective control (Kakati and Nath, 2014; Legg et al., 2014; Loebenstein and Katis, 2014).

Materials and Methods

Seed Materials and Insecticeds

Pure and viable tomato variety "Aryaman" seeds were gathered from the local market in Latur for the current study. The following insecticides were sprayed on tomatoes at the acceptable concentrations to prevent whiteflies. The necessary insecticides for the experiment were bought at the local market in Latur.

Botanicals

In order to successfully manage whiteflies in tomatoes and related crops, the following botanical extracts were applied in the suggested dosages in the current study. The College of Agriculture, Latur Farm, and a local market in Latur provided the botanicals needed to carry out the experiment. The following botanicals were used to control whiteflies in tomatoes and allied crops at the prescribed dosages.

Bioagents

In the current study, the bioagents were used in the recommended dosages to effectively control whiteflies in tomatoes and related crops. The bioagents required to conduct the experiment were obtained from the Spawn Production Unit, Department of Plant Pathology, V.N.M.K.V., Parbhani.

Chitosan treatment

The chitosan solution (1 mg/ml) made in 100 mM acetate buffer (pH 4.5) and adjusted with 1 N NaOH to pH 6.5 was sprayed on the upper and lower surfaces of the leaves at 25 DAS.

Experimental site

An experiment was carried out on the experimental farm of the Department of Plant Pathology, College of Agriculture Latur, during the Kharif seasons of 2025-2026. Three replications of the tomato cultivar "Aryaman," which is prone to leaf curl, were cultivated using a randomized block design (RBD).

Details of the experiment

Statistical Analysis

A statistical analysis was performed on the data gathered from different field experiments. Percentage data were transformed into arcsine values prior to analysis, and standard error (S.E.) and critical difference (C.D.) at the 5% significance level were computed using the approach of Panze and Sukhatme (1978).

Results and Discussion

Disease incidence

The results, as detailed in Table 1, demonstrate that all evaluated treatments had a statistically significant effect on the management of tomato leaf curl virus (ToLCV) under field conditions. Per cent disease incidence recorded before the first spray ranged between 5.33% and 6.67% and was statistically non-significant (NS), indicating uniform initial disease pressure across all treatment groups and the untreated control. However, after the first and second sprays, the applied treatments exhibited significant variations in disease incidence compared to the control group.

After the first spray, ToLCV incidence across all treatments ranged from 2.67% to 14.47%, compared to 22.67% in the untreated control (T 9 ). Treatment T 2 (Thiamethoxam @25% WG) emerged as the most effective treatment, recording the significantly lowest incidence (2.67%). This was followed by T 1 (Imidacloprid 17.8 SL @ 0.1%) at 4.00% and T 6 (Pseudomonas fluorescens + Chitosan) at 6.67%. Higher incidence levels among the treatments were observed in the botanical plots, specifically T 3 (Neem oil @ 5ml/L) at 13.33% and T 4 (Karanj oil @ 5ml/L) at 14.47%, while the untreated control exhibited the maximum disease prevalence.

Observations after the second spray showed a disease incidence range of 1.33% to 17.33% among the treated plots, whereas the untreated control reached 36.00%. Treatment T 2 remained the most superior treatment, maintaining the lowest incidence (1.33%). It was closely followed by T 1 (2.67%), T 6 (5.33%), and T 8 (Beauveria bassiana + Chitosan) at 6.67%. Treatments T 3 and T 4 recorded higher incidence rates of 14.67% and 17.33% respectively, though all treatments remained significantly more effective than the untreated control, which recorded the highest overall incidence of ToLCV.

In terms of overall effectiveness, the maximum per cent disease reduction over the control was achieved by T 2 (93.18%), followed closely by T 1 (88.63%). Notably, combining biocontrol agents with chitosan enhanced their efficacy; T 6 (Pseudomonas fluorescens + Chitosan) and T 8 (Beauveria bassiana + Chitosan) achieved substantial disease reductions of 79.55% and 75.00% respectively, visibly outperforming their standalone applications (T 5 at 68.20% and T 7 at 63.63%).

Whitefly Population

The results, as detailed in Table 2, demonstrate that every treatment applied had a statistically significant effect on the whitefly population per plant under field conditions. The whitefly population recorded prior to the first spray was statistically nonsignificant (NS), ranging from 3.00 to 4.00 per plant, indicating no initial differences between the treatment groups and the unsprayed control. However, after the first and second sprays, the treatments showed significant variation compared to the control group.

After the first spray, the whitefly population across all treatments ranged from 0.47 to 3.80 per plant, compared to 4.40 in the untreated control. T 2 (Thiamethoxam @25% WG) emerged as the most effective treatment, recording the significantly lowest population (0.47 whiteflies/plant). This was followed by T 1 (Imidacloprid 17.8 SL @ 0.1%) with 1.27, and T 6 (Pseudomonas fluorescens + Chitosan) with 1.73. Higher populations were observed in the botanical treatments, specifically T 3 (Neem oil @ 5ml/L) at 3.26 and T 4 (Karanj oil @ 5ml/L) at 3.80, while the untreated control exhibited the maximum whitefly prevalence. Observations after the second spray showed a range of 0.13 to 3.93 whiteflies per plant among treatments, while the untreated control reached 5.40. T 2 remained the most superior treatment with the lowest population (0.13). It was followed by T 1 (0.73), T 6 (1.27), and T 8 (Beauveria bassiana + Chitosan) with 1.73. Treatments T 3 and T 4 recorded 3.33 and 3.93 respectively, with the untreated control recording the highest overall whitefly population. In terms of overall efficacy, T 2 recorded the maximum per cent reduction over the control (93.88%), followed closely by T 1 (79.59%). The integration of chitosan with biocontrol agents notably enhanced their performance; T 6 (Pseudomonas fluorescens + Chitosan) achieved a 69.39% reduction compared to 51.02% in T 5 alone, and T 8 (Beauveria bassiana + Chitosan) achieved a 60.61% reduction compared to 42.86% in T 7 alone. The botanical treatments (T 3 and T 4 ) recorded the lowest overall reductions at 32.65% and 21.02%, respectively. [5] , Walia et al. (2015) [11] , and Sahu et al. (2018) [10] . The enhanced disease reduction observed when combining chitosan with biocontrol agents such as Pseudomonas fluorescens attributed to the synergistic induction of systemic resistance (ISR) and antiviral defense enzymes in tomato plants was similarly documented by Mishra et al. (2014) [7] and El-Dougdoug et al. (2018) [2] . Furthermore, the moderate but statistically significant suppression of ToLCV incidence using botanical formulations like neem oil and karanj oil, compared to untreated control plots, is consistent with findings reported by Singh et al. (2012) and Naqvi et al. (2019) [8] . Imidacloprid (0.02%) and thiamethoxam (0.005%) both showed strong systemic suppression of Bemisia tabaci, with imidacloprid exhibiting prolonged persistence against viral symptom expression under varying seasonal conditions. Kumar et al. (2012) [4] reported similar results regarding the comparative efficacy of neonicotinoids across multi-season field evaluations. Additionally, both imidacloprid and thiamethoxam dramatically inhibit phloem sap consumption by about 90%, according to behavioral and electropenetrography (EPG) investigations by He et al. (2013) [3] and Miranda et al. (2016) [6] . Since the tomato leaf curl virus (ToLCV) is mostly infected during prolonged periods of vascular probing and feeding, this feeding inhibition is essential for disease control. Furthermore, the increased mortality and population decrease seen when chitosan is combined with bacterial antagonists (Pseudomonas fluorescens) or entomopathogenic fungi (Beauveria bassiana) are consistent with research by Sahayaraj et al. (2018) [9] and Mishra et al. (2014) [7] , who attributed this synergy to chitosan's capacity to both disrupt insect cuticle integrity and stimulate host plant defense pathways.

Conclusion

The remarkable effectiveness of chemical insecticides in reducing the virus and its vector was demonstrated by field tests evaluating integrated management options. With the lowest whitefly population (0.13 per plant) and illness incidence (1.33%), as well as a 93.18% disease reduction over the control, thiamethoxam 25% WG proved to be the most successful and economically feasible treatment.

Disclaimer (Artificial Intelligence)

Author(s) hereby declare that no generation at technologies such as large language models (ChatGpt, COPILOT, etc.) and text to image generators have been used during the writing or editing of this manuscript.

Acknowledgement

AcknowledgementsWe are thankful to the department of Plant Pathology, College of Agriculture, Latur for providing us with the laboratory to complete this study. We would like to express our gratitude to the guide, professors, head of the department, laboratory staff and other faculty members for their help, support and kind cooperation during the research period.

References

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