Field evaluation of different fungicides, bio-agent and botanical against early blight of tomato caused by Alternaria solani

Introduction

Tomato (Solanum lycopersicum) constitutes one of India's commercially rewarding vegetable crops of major significance. It belongs to the family Solanaceae. In India, the tomato is often called "poor man's orange" or Vilayati Baigan. Introduced in the early 19th century, it is now the world's third most cultivated vegetable after potato and sweet potato. Widely recognized as a protective food, the tomato is packed with essential nutrients, including minerals, vitamins, organic acids and health-promoting compounds like lycopene, beta-carotene, phenols and flavonoids. Lycopene, in particular, functions as a potent antioxidant associated with a lowered risk of cardiovascular diseases and certain cancers. In the year 2023-24, India recorded a total tomato production of 21.32 million tonnes cultivated over an area of 854 thousand hectares, resulting in an average productivity of approximately 24.96 tonnes per hectare. (Anonymous, 2024) [2]. In 2023-24, Madhya Pradesh recorded the largest tomato-cultivated area at 119.67 '000 ha, followed by Odisha (98.13 '000 ha), Gujarat (66.57 '000 ha), Bihar (63.20 '000 ha) and Karnataka (62.43 '000 ha). Among the major tomatoproducing states in India, Odisha ranked fifth, contributing significantly to the national output. The pathogen responsible for tomato early blight, Alternaria solani, was first identified and described by Ellis and Martin (1882). The pathogen survives on infected plant debris (leaves, stems) and soil, and its spores germinate on crop residue or active lesions. The disease spreads through several means-splashing rain, air currents, wind-blown soil particles and irrigation water (Maurya et al., 2022) [7] . The disease is particularly aggressive during the fruiting stage of the crop (Chohan et al., 2015) [4] . Tomato crops are highly susceptible to various diseases caused by fungal, bacterial, viral, nematode and abiotic factors. Important fungal diseases include late blight (Phytophthora infestans), fusarium wilt (Fusarium oxysporum f. sp. lycopersici) and septoria leaf spot (Septoria lycopersici). Among the various fungal infections affecting tomato crops, early blight stands out as a major concern. The disease is incited by Alternaria solani (Ellis and Martin) Jones and Grout, posing a major constraint to tomato production by substantially reducing both yield and fruit quality. The disease can affect the crop at any stage of its growth, making it a persistent and challenging threat (Abada et al., 2008) [1] . Dense plantings, frequent rains, and long periods of leaf wetness favor epidemics. (Gondal et al., 2012) [6] . According to Parvin et al. (2021) [10] , the disease can reduce yield by 50 to 86% and hinder seedling establishment by 20 to 40%. The effective management of early blight disease is crucial to ensure sustainable tomato production in Western Odisha. Fungicides used at present are very costly and are not controlling the disease satisfactorily. Hence, it is necessary to evaluate new fungicides in the field to combat the disease satisfactorily. There is lack of information on the impact of bioagents and plant products against the pathogen and it is necessary to identify a suitable bio-agent and plant product to prevent health hazards due to fungal toxicants. Therefore, the present work was designed to manage the disease using different fungicides, bio-agent and botanical under field condition in Western Odisha.

Materials and Methods

A field experiment was undertaken during Rabi, 2024-25, at the College of Agriculture, Chiplima, to evaluate the efficacy of different fungicides, bio-agent and botanical against early blight of tomato. The experiment was laid out in a randomized block design with nine treatments and three replications. The variety used was Pusa Rubi. The different treatments used were as follows: T 1 -2 sprays of multineem @ 0.5% T 2 -Soil application of Trichoderma viride @2.5 kg/ha T 3 -2 sprays of tebuconazole @ 0.1% T 4 -2 sprays of difenoconazole @ 0.1% T 5 -2 sprays of carbendazim 12% + mancozeb 63% @ 0.2% T 6 -2 sprays of mancozeb @ 0.3% T 7 -2 sprays of copper oxychloride @ 0.3% T 8 -2 sprays of hexaconazole @ 0.1% T 9 -Untreated control.

Twenty one days old tomato seedlings were transplanted into the main field during November 2024, maintaining a spacing of 60 × 45 cm. Recommended doses of fertilizer were applied in each plot and standard agronomic practices were followed to raise the crop. After initiation of the disease, the first spray was applied on the foliage. Two sprayings of each fungicide and botanical were applied at 15-day intervals. Trichoderma viride was applied in the soil. Disease intensity was assessed using the 0-5 scale (0= No disease in the foliage, 1= Small irregular spots covering less than 5% leaf area, 2= Small irregular spots covering 5.1 to 10% leaf area, 3 =lesions covering 10.1 to 25% leaf area, 4= lesions covering 25.1 to 50% leaf area, 5= lesions covering more than 50% leaf area) proposed by (Mayee and Datar, 1986) [8]. Yield data were also collected and all observations were subjected to statistical analysis. Disease severity was calculated by using the following formula (Chester, 1959; Wheeler, 1969) [3,12] Results and Discussion A field experiment was carried out during Rabi, 2024-25, at the College of Agriculture, Chiplima, to evaluate the efficacy of different fungicides, bio-agent and botanical against early blight disease of tomato. The data pertaining to disease severity and yield were recorded and presented in Table 1. The data revealed that all the treatments tested were effective in reducing the severity of early blight disease compared to the untreated control. Among the different fungicides evaluated, difenoconazole 25% EC recorded the lowest PDI of 14.23%, resulting in a maximum disease reduction of 77.34% over the control. This was followed by the fungicide tebuconazole, which also performed well in reducing disease severity with a PDI of 18.10% and 71.18% disease reduction over control. Similarly, plots sprayed with hexaconazole 5% SC showed good results, recording a PDI of 23.20% with 63.06% disease reduction over control. Moderate control was observed with carbendazim 12% + mancozeb 63% WP and mancozeb 75% WP, which recorded PDI values of 28.30% and 32.10%, respectively. Treatments with copper oxychloride gave a PDI of 38.30%. However, the botanical and biological treatments, Multineem (neem oil-based EC) and Trichoderma viride 1.5% WP), were comparatively less effective in controlling early blight disease under field conditions, showing higher PDI values of 44.50% and 48.20%, respectively. Data on effect of different fungicides, bio-agent and botanical on fruit yield of tomato were recorded and presented in Table 1. There has been a significant increase in fruit yield of tomato in all treatments over the control. Plots treated with difenoconazole recorded the highest yield of 225.10 q/ha, which was 87.27% greater than that of the untreated control (120.20 q/ha). This was followed by tebuconazole (210.20 q/ha) and hexaconazole (200.30 q/ha), which showed yield increases of 74.87% and 66.63%, respectively, over control. Carbendazim 12% + mancozeb 63% WP and mancozeb 75% WP also gave good yields of 194.50 q/ha and 188.60 q/ha. On the other hand, the botanical Multineem and the bioagent Trichoderma viride recorded comparatively lower yields of 162.20 q/ha and 155.40 q/ha, respectively. An economic analysis of the benefit-cost ratio for different fungicides, botanical and bio-agent is presented in Table 2. The analysis highlights pronounced differences in profitability among the treatments. Difenoconazole 25% EC delivered the best overall returns, generating a gross income of Rs. 2,25,100, a net income of Rs. 1, 63,964 and the highest B:C ratio of 3.68. This was followed by tebuconazole 25.9 EC, which produced a gross income of Rs. 2,10,200, net returns of Rs. 1,48,200 and a B:C ratio of 3.39. The systemic fungicide hexaconazole 5% SC also performed well, with gross and net incomes of Rs 2,00,300 and Rs. 1,38,504, respectively, yielding a B:C of 3.24. The botanical Multineem and the bio-agent Trichoderma viride were less lucrative, with B: C ratios of 2.61 and 2.49, respectively. The untreated control recorded the lowest net return (Rs. 50,721) and the poorest B: C ratio of 1.73. Our results are in line with the findings of Nagesh, et al. (2019) [9] who reported that difenoconazole was the most effective fungicide for managing early blight and boosting tomato yield followed by tebuconazole under field condition. Sreenivasulu et al. (2019) [11] also found that tebuconazole was most effective fungicide in reducing disease severity against early blight of tomato and increasing yield under field condition. Even though T. viride and Multineem were found to be less effective in managing early blight, they may play a valuable role in integrated disease management of the disease. Therefore, biological agents and botanicals need to be tried on a larger scale to manage the disease and then recommended to the farmers.

Conclusion

The overall findings of the study clearly indicated that difenoconazole was the most effective fungicide both in terms of disease management and economic return, followed by tebuconazole and hexaconazole. Even though, botanical and bioagent were not much effective in reducing disease severity as compare to fungicidal treatment, but they performed better in reducing disease severity as compare to control.

References

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