Integrated SDHI-QoI Fungicide Strategy for Effective Foliar Disease Management in Blackgram

Introduction

Blackgram (Vigna mungo (L.) Hepper) is an important short-duration pulse crop belonging to the family Fabaceae. It plays a significant role in Indian agriculture due to its nutritional richness, ability to fix atmospheric nitrogen and soil fertility improvement. It consists of around 24% protein, along with carbohydrates, vitamins and essential minerals such as calcium, phosphorus and iron, making it a vital component of vegetarian diets (Ali and Gupta 2012) [1] . India is the leading producer of blackgram, cultivating nearly 3.5 million hectares and producing about 2.0 million tonnes annually (Singh et al. 2016) [16] . In Karnataka, it is widely grown in the northern transitional zone including Dharwad, Belagavi, Gadag and Haveri districts, where it forms an integral part of the rainfed cropping system. Although India is the leading producer of Blackgram, there is gap in its productivity due to several foliar fungal diseases that cause considerable yield losses. Among these, Cercospora leaf spot (Cercospora canescens), Anthracnose (Colletotrichum truncatum) and Powdery mildew (Erysiphe polygoni) are the most destructive diseases, often reducing yield by 30-60% under favorable weather conditions (Sharma, 1999; Pathak and Ram, 2013; Balol et al., 2020) [14,6] . The co-formulated product Fluxapyroxad 167 g/L + Pyraclostrobin 333 g/L 500 SC (Priaxor 500 SC) offers both protective and curative activity. In addition to disease suppression, this formulation promotes plant vitality through improved photosynthetic efficiency, delayed senescence and enhanced yield potential. Considering the recurring incidence of foliar diseases in blackgram, the present investigation was undertaken to evaluate the field efficacy and crop safety of Priaxor 500 SC under the conditions of northern Karnataka.

Materials and Methods

A field investigation was carried out during the

Experimental design and layout

The experiment was laid out in a Randomized Block Design (RBD) comprising seven treatments, each replicated three times. Individual plots measured 5 m × 4 m (20 m²), maintaining a spacing of 30 cm between rows and 10 cm between plants. Standard cultivation practices such as recommended seed treatment with Rhizobium inoculant, basal fertilizer application, weeding and intercultivation were uniformly adopted in all plots to ensure normal crop growth. No insecticides were used during the experimental period to avoid interaction with fungicidal treatments.

Treatment details

Tr.no Treatments

T1

Fluxapyroxad 167 g/l + Pyraclostrobin 333 g/l SC @ 100 ml/ha T2 Fluxapyroxad 167 g/l + Pyraclostrobin 333 g/l SC @ 200 ml/ha T3 Fluxapyroxad 167 g/l + Pyraclostrobin 333 g/l SC @ 300 ml/ha T4 Fluxapyroxad 300 g/l SC T5 Pyraclostrobin 20% WG T6

Captan 70 & + Hexaconazole 5% WP T7 Control/ Untreated check

Disease recording and assessment

The incidence and severity of Cercospora leaf spot, Anthracnose and Powdery mildew were recorded before the first spray, 14 days after each spray and at harvest. Disease severity was scored visually using standard rating scales:  Cercospora leaf spot and Anthracnose were rated on a 0-9 scale (Mayee and Datar, 1986) [12] .  Powdery mildew was scored on a 0-5 scale (Gawande and Patel, 1987) [9] .

The Percent Disease Index (PDI) was computed using the formula given by wheeler (1969) [19]: PDI = sum of the individual disease ratings no of leaves observed × maximum disease grade × 100

Ten plants per replication were randomly selected for scoring and the mean PDI values were calculated for each treatment before subjecting them to statistical analysis.

Phytotoxicity evaluation

Phytotoxicity of Priaxor 500 SC was assessed at higher concentrations of 300, 375, and 600 ml/ha, along with an untreated control. Ten plants from each plot were tagged and examined for possible injury symptoms such as leaf burn, wilting, vein clearing, necrosis, epinasty and hyponasty at 1, 3, 5, 7 and 10 days after spraying. Observations were recorded using a 0-10 scale, where 0 represented no visible symptoms and 10 denoted complete damage. The absence of any phytotoxicity symptoms indicated the crop safety of the tested formulation.

Yield assessment

At harvest, the grains from each plot were collected, dried and weighed to obtain plot-wise yields, which were then converted to quintals per hectare (q/ha). The percentage increase in yield over the untreated check was computed to determine the productivity advantage associated with each treatment.

Statistical analysis

All the experimental data was subjected to analysis of variance (ANOVA) suitable for RBD. Treatment means were compared using the critical difference (CD) at 5% probability level (p = 0.05) as described by Gomez and Gomez (1984) [10] . Percentage data was transformed to arcsine values before analysis to normalize variance. Statistical interpretation was based on significant differences among treatments and their relative efficacy. 1). The enhanced control could be attributed to the dualaction mode of the SDHI and QoI components that inhibit fungal respiration and spore germination (Fisher et al., 2018).

Results and Discussion

Effect on Anthracnose

Similarly, Priaxor 500 SC @ 300 and 200 ml/ha doses (T [3,2] who reported effective control of Colletotrichum spp. in pulses using fluxapyroxad-based formulations.

Effect on Powdery Mildew

The application of Priaxor 500 SC at 300 and 200 ml/ha doses (T 3 and T 2 ) reduced powdery mildew severity to 18.21 and 18.60 % respectively, compared to 33.25 % in the untreated check (T 7 ). Both treatments recorded over 44% reduction in disease intensity (Table 1). The superiority of Priaxor is due to its translaminar movement and systemic protection providing both preventive and curative effects (Venugopal et al., 2020; Channaveeresh et al., 2013) [18,7] . Similar results have been reported on other crops such as chickpea (Basamma et al., 2021: Sangeeta et al., 2022) [13] , urdbean (Balol et al., 2020) [4] , Onion (Shilpakumari et al., 2011), Mango (Vamshika et al., 2023), Rice (Balol et al., 2022) [5,15,17] and Greengram where fungicide application has reduced the disease and increased the yield.

Effect on yield

Significant difference in grain yield was observed among treatments. The highest yield was recorded in Priaxor 500 SC @ 300 ml/ha (9.07 q/ha) followed by 200 ml/ha (8.83 q/ha) doses both statistically on par with each other and showing yield increase of 78.5% and 73.9% over control.

Standard checks showed comparatively lower yields (7.66-7.88 q/ha) (Table 2; Fig. 1). The yield advantage may be attributed to prolonged disease control, improved leaf greenness, and enhanced photosynthetic efficiency (Kumar et al., 2021) [11] .

Phytotoxicity

No phytotoxic symptoms such as leaf injury, wilting or necrosis were observed at any tested concentration of Priaxor 500 SC, confirming the crop safety of the formulation.

Conclusion

The study clearly demonstrated that Priaxor 500 SC (Fluxapyroxad 167 g/l + Pyraclostrobin 333 g/l) @ 200 ml/ha is optimum for effective management of major foliar fungal diseases of blackgram including Cercospora leaf spot, Anthracnose and Powdery mildew. The product not only reduced disease incidence significantly but also enhanced grain yield without showing any phytotoxic symptoms, thereby ensuring sustainable urdbean production.

References

1. Ali M, Gupta S. Carrying capacity of Indian agriculture: pulse crops. Curr Sci. 2012;102(6):874-81.
2. Balasubramanian R, Nirmala S, Karthikeyan G. Evaluation of new fungicide molecules against anthracnose disease of blackgram. J Mycopathol Res. 2019;57(4):313-8.
3. Balol G, Math G, Mogali S, Kumbar B, Channakeshava C, Iramma, Goudar V. Chemical management of foliar fungal diseases of blackgram (Vigna mungo (L.) Hepper) in Karnataka. Int J Trop Agric. 2021;39(3):291-6.
4. Balol G, Math G, Mogali S, Kumbar B, Revadi N. Chemical management of powdery mildew caused by Erysiphe polygoni DC on urdbean and its economic analysis. Int J Chem Stud. 2020;8(6):256-9.
5. Balol G, Talekar SC, Satish RG. Efficacy of various fungicides on the management of rice blast disease caused by Pyricularia oryzae (Cav.) under field condition in Dharwad district of Karnataka. Int J Plant Sci. 2022;17(2):214-7.
6. Kumbar B, Balol G, Lokesh BK, Kukanur S, Nayak H. Field evaluation of different fungicides against Uromyces ciceris-arietini causing rust in chickpea in northern Karnataka. J Pharmacogn Phytochem. 2021;10(1):896-900.
7. Channaveeresh SA, Kulkarni MS, Desai SA. Efficacy of fungicides and bioagents against powdery mildew of greengram. Karnataka J Agric Sci. 2013;26(4):568-70.
8. Fisher N, Meunier B, Leroux P. Molecular basis of resistance to QoI fungicides in plant pathogens. Pest Manag Sci. 2018;74(3):483-90.
9. Gawande VL, Patel PN. Assessment of powdery mildew disease of greengram. Indian Phytopathol. 1987;40(3):402-4.
10. Gomez KA, Gomez AA. Statistical procedures for agricultural research. 2nd ed. New York: John Wiley and Sons; 1984. 680 p.
11. Kumar S, Sharma P, Raj S. Physiological basis of yield enhancement in pulse crops through fungicidal applications. Legume Res. 2021;44(7):825-31.
12. Mayee CD, Datar VV. Phytopathometry. Technical Bulletin-1. Parbhani (MH): Marathwada Agricultural University; 1986. 218 p.
13. Sangeeta N, Prabhu HV, Balol G. In vitro evaluations of fungicides against Sclerotium rolfsii Sacc. causing collar rot of chickpea. Int J Plant Sci. 2022;17(2):12832.
14. Sharma SK. Studies on powdery mildew of mungbean and its management. J Mycol. 2021;29(2):204-6.
15. Shilpakumari MV, Chandrashekar SC, Balol GB, Divya BL, Narendrappa T, Pramodh HP. Evaluation of fungicides and botanicals against Alternaria porri the cause of purple blotch disease in onion. Res J Agric Sci. 2011;2(4):80-5.
16. Singh G, Singh A, Singh P, Singh IS. Performance of greengram varieties in different agro-climatic zones of India. Legume Res. 2016;39(4):601-6.
17. Vamshika VN, Kalappanavar IK, Gurupad B, Patil VS. Management of mango anthracnose caused by Colletotrichum gloeosporioides (Penz.) Penz. & Sacc. J Farm Sci. 2023;36(1):59-61.
18. Venugopal P, Reddy MS, Raghavendra NV. Efficacy of strobilurin + SDHI fungicides in the management of powdery mildew in blackgram. Plant Arch. 2020;20(2):5379-83.
19. Wheeler BEJ. An introduction to plant diseases. London: John Wiley and Sons; 1969. 301 p.