Potato (Solanum tuberosum L.) is one of the most important food crops globally, ranking fourth after maize, wheat and rice in terms of production and consumption. It is a staple crop with high economic and nutritional value. It is a nutritious tuber vegetable and rich source of starch, vitamins especially (C and B1) and minerals (Zaheer and Akhtar, 2016). In India, it occupies a prominent place in vegetable production, particularly in the Indo-gangetic plains, including eastern Uttar Pradesh, which is a major potato-growing region (Singh et al., 2021).  One of the major biotic constraints affecting potato cultivation is black scurf, caused by the soil-borne fungal pathogen Rhizoctonia solani (Kuhn) also causes root rot, stem canker and damping- off disease complexes of potato crop (Bains et al., 2002).
       
This disease is prevalent in almost all potato-growing areas and causes considerable yield and quality losses. In India, it is responsible for 10-25% yield loss (Sharma, 2015) and in severe cases, it can cause up to 50% yield reduction (Verma et al., 2021). Yield loss is directly related to disease severity, with tubers having over 10% sclerotia coverage showing markedly reduced yields compared to healthy tubers (Jain et al., 2024). Eastern Uttar Pradesh is one of the major potato-growing regions, share 18.5% area and contribute approximately 16.5% production in overall production of potato in Uttar Pradesh (Statistical Abstract, UP, 2023), where farmers face serious challenges due to black scurf and stem canker. This pathogen produces symptoms on both above and below-ground plant parts of potato. Black scurf appears as hard, black sclerotia on the surface of the tuber, which reduces marketability and yield, while stem canker affects underground stems, leading to poor crop stand, stunted growth and reduced tuber formation (Banville, 1989; Tsror, 2010). Temperature and soil moisture play an important role in disease development. The optimum temperature is 20-25^oC and moisture is 20% for its growth (Kiptoo et al., 2021). The shallow sowing of potato tubers resulting minimum black scurf incidence and severity compared to deep sowing. The disease is negatively correlated with evening soil temperature but positively correlated with morning temperature and soil moisture (Kumar et al., 2018).
       
The management of R. solani is challenging due to its broad host range, soil persistence and lack of resistant potato cultivars. Cultural practices and crop rotation alone are often insufficient in limiting the disease effectively under field conditions. Patel and Singh (2021) reported the use of organic approaches, such as bio-agents and organic amendments, for the management of black scurf of potato, however, their effectiveness remains limited. Among the various control strategies, chemical management through fungicidal seed (tuber) treatment remains one of the most effective and widely adopted practices (Nagaich et al., 2005; Dey et al., 2014). Several fungicides, including Pencycuron, Penflufen, Thifluzamid and combinations like Mancozeb + Carbendazim, have shown promising results in managing R. solani in different agro-climatic zones (Nema and Sharma, 2011; Lal et al., 2020). However, data specific to eastern Uttar Pradesh, with its unique climate and soil conditions, are limited.
       
This study was undertaken to evaluate the comparative efficacy of tested fungicidal seed tuber treatments against black scurf of potatoes over two consecutive growing seasons in eastern Uttar Pradesh. The results aim to support region-specific chemical disease management strategies to improve potato productivity and tuber quality.

The field experiments were carried out with various fungicides along with treated tubers and untreated diseased tubers (control) at Main Experimental Station (MES), Vegetable Science andUAT Kumarganj Ayodhya for two consecutive years (2022-23 and 2023-24) using a randomized block design (RBD) with five treatments (Table 1) to evaluate their fungicidal efficacy against black scurf. The black scurf affected tubers (Fig 1) were collected from field.




       
Tubers of variety, Kufri Sindhuri were dipped in solutions of tested fungicides for 30 minutes before sowing along with untreated diseased (control) Fig 2 and spread in shade till the tubers got dried completely. Tubers of potato variety Kufri Sindhuri were planted with 60 x  20 cm spacing. Each treatment had 3 m x 2 m plot in a Randomized Block Design (RBD) with five replications. All the recommended and cultural practices were followed to raise the crop (Fig 3) up to 90 days after which the haulms were cut. The harvesting of tubers were carried out after 10 days of haulms cutting. The evaluation of efficacy of tested fungicides against black scurf disease was carried out according to 0-4 disease rating scale was used and crops were harvested at 100-105 days after sowing. After harvesting, 50 tubers were randomly selected from each treatment plot, tubers were washed and black scurf disease incidence, intensity (index) and tuber yields (q/ha) were recorded and then disease index was calculated as per the scale (Table 2) and method used by Somani (1986).
Per cent Disease Index/Intensity was calculated by-
 

                                          

  
The per cent disease incidence (PDI) was calculated by using the formula proposed by Ahmad et al., (1995) as described below: -
 

 

  
Statistical analysis
 
The recorded data sets were statistically analysed using OPSTAT software (Sheoran, 2006) where the data sets were subjected to one way ANOVA at the 5% level of significance.

The results of the field experiments carried out during the rabi seasons of 2022-23 and 2023-24 to assess the efficacy of tested fungicidal tubers treatments against black scurf in potatoes are presented in Table 3 and Table 4.



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Per cent disease incidence (tubers infected by black scurf)
 
During 2022-23, a significant reduction in disease incidence was observed in all treated plots compared to the untreated control (T1), which recorded the highest incidence at 65.33%. Among the treatments, T2 (Pencycuron 22.9 SC @ 0.35%) recorded the lowest incidence at 27.31%, followed by T3 (32.37%) and T5 (33.06%). The treatment with Thifluzamid (T4) also significantly reduced incidence to 38.61%. These differences were statistically significant at the 5% level (CD = 1.67%). In 2023-24, a similar trend was observed. T2 once again resulted in the lowest disease incidence (5.20%), followed closely by T4 (6.21%) and T3 (8.10%). The control plot recorded 21.70% incidence. The differences among treatments were significant (CD = 1.90%), confirming the consistent performance of the fungicidal treatments across both years.
 
Per cent disease index (tuber surface area covered by black scurf)
 
The per cent disease index was significantly affected by fungicidal treatments in both years. In 2022-23, the highest disease index was observed in the untreated control (45.66%), while T2 recorded the lowest index (21.04%), followed by T3 (22.48%), T4 (26.78%) and T5 (30.31%). The differences were statistically significant (CD = 1.07%). In 2023-24, the per cent disease index followed a similar pattern, with the lowest in T4 (5.36%), followed by T2 (7.50%), T5 (8.60%) and T3 (9.60%). The control plot showed a higher index of 32.50%. The results demonstrated significant improvement in disease suppression with all fungicidal treatments (CD = 1.39%).
 
Total tuber yield (q/ha)
 
In 2022-23, all fungicide-treated plots recorded significantly higher yields compared to the untreated control (183.40 q/ha). T2 (Pencycuron) recorded the highest yield (233.40 q/ha), followed by T5 (211.10 q/ha), T4 (205.60 q/ha) and T3 (194.50 q/ha). The differences were statistically significant (CD = 3.16 q/ha). In 2023-24, although statistical analysis revealed that yield differences among treatments were not significant (CD = NS), numerical trends were consistent with the previous year. T2 yielded the highest (243.00 q/ha), followed by T4 (237.00 q/ha), T3 (235.50 q/ha) and T5 (233.10 q/ha), compared to 220.40 q/ha in the untreated control. The increase in yield in treated plots can be attributed to effective disease suppression.
       
Among the various tested fungicides, Pencycuron 22.9 SC (T2) consistently emerged as the most effective treatment, significantly reducing both the percent disease incidence and disease index, while simultaneously improving tuber yield. Pencycuron, a phenylurea fungicide, is known for its high specificity and effectiveness against R. solani, particularly in preventing hyphal growth and infection at early stages (Stevenson et al., 2001).  Similar result found that treating potato seed tubers with either pencycuron at 0.057% active ingredient or a 3% boric acid spray before planting effectively controlled black scurf disease without hindering crop emergence (Arora, 2013). The lowest disease incidence and index recorded in T2 during both years, along with the highest yield; reinforce its potential as a reliable fungicidal option in the integrated management of R. solani.
       
Thifluzamide (T4), a SDHI (succinate dehydrogenase inhibitor) fungicide, also exhibited consistent and promising results, especially in the second year where it recorded the lowest disease index (5.36%). Thifluzamide interferes with fungal respiration, effectively limiting lesion development and sclerotia formation (Ajayi-Oyetunde and Bradley, 2018). Its performance in this study corroborates earlier findings by Yellareddygari et al., (2014), who reported strong efficacy of Thifluzamide against soil borne pathogens inciting R. solani. The performance of T3 and T5 treatments, while slightly lesser to T2 and T4, also contributed significantly to disease suppression and yield enhancement. These results suggest that a range of fungicidal options exists and the choice may be tailored based on availability, cost and local disease pressure. The substantial reduction in percent disease incidence from 65.33% in untreated control (T1) to as low as 5.20% with T2 in 2023-24, evaluate effectiveness of chemical seed/tuber treatment as a disease management strategy. Such reductions are critical not only for minimizing losses but also for improving tuber quality and marketability, which are heavily impacted by black scurf blemishes (Lees et al., 2010).
       
Moreover, the yield enhancement observed in treated plots, although statistically non-significant in the second year, consistently followed the trend of reduced disease pressure. This aligns with previous studies which indicated that effective suppression of R. solani leads to improved plant vigor and resource allocation, resulting in better yield outcomes (Bandyopadhyay et al., 2013). However, considering the potential for resistance development and environmental impact, periodic rotation of fungicides and integration with cultural and biological methods is recommended for sustainable disease management (FRAC, 2024).

Across both seasons, Pencycuron (T2) consistently showed superior performance in reducing disease incidence and severity while improving tuber yield. Thifluzamid (T4) and Penflufen (T3) were also effective, with Thifluzamid showing excellent disease suppression in 2023-24. The combination treatment of Mancozeb + Carbendazim (T5) showed intermediate results but was better than untreated control in both years. Overall, the data support the integration of fungicidal tubers treatment, particularly with Pencycuron and Thifluzamide, as an effective strategy in the holistic management of R. solani in Eastern Uttar Pradesh and similar agro-ecological regions.

The present study was supported by ICAR-AICRP-Potato for financial grant to conduct research work. The authors are highly grateful to AICRP-Potato and thankful to Department of Vegetable Science andUAandT Kumarganj, Ayodhya, Uttar Pradesh, India for providing necessary facilities.
 
Disclaimers
 
The views and conclusions expressed in this article are solely those of the authors and do not necessarily represent the views of their affiliated institutions. The authors are responsible for the accuracy and completeness of the information provided, but do not accept any liability for any direct or indirect losses resulting from the use of this content.
 
Author’s contribution
 
All the authors mentioned above have significantly contributed to the work in a direct and intellectual manner and have given their approval for its publication.

The authors declare that there is no conflict of interest.