Integrated management of Phytophthora blight in pigeonpea under farmers’ field conditions

Introduction

Pigeonpea (Cajanus cajan L.) is one of the most important pulse crops in India, playing a crucial role in ensuring nutritional security by providing dietary protein and improving soil fertility through biological nitrogen fixation. India accounts for nearly 70-75% of the global pigeonpea area and production; however, crop productivity remains low relative to its potential due to several biotic and abiotic constraints (FAOSTAT, 2023; ICAR-IIPR, 2022) [3, 8] . Among these constraints, diseases caused by soil-borne pathogens are a major threat to sustainable pigeonpea production, particularly in rainfed agro-ecosystems (Kannaiyan et al., 1984; Sharma et al., 2015) [9,14] . In Maharashtra, one of the major pigeonpea-growing states in India, the crop covered 11.11 lakh hectares, with production of 9.82 lakh tonnes and an average productivity of 884 kg ha⁻¹ during 2023-24, which is still below the achievable yield under improved management practices (DES, Maharashtra, 2024). Phytophthora blight, caused by Phytophthora drechsleri f. sp. cajani, is a highly destructive disease of pigeonpea and is widely prevalent in regions with high rainfall and temporary waterlogging (Sharma et al., 2012; Ghosh et al., 2019) [13,5] . The disease can infect the crop at all growth stages, causing rapid wilting, stem lesions, root rot, plant mortality, and substantial yield losses. Under favourable environmental conditions, yield losses of 20 to 60% have been reported (Kannaiyan et al., 1984; Pande et al., 2013) [9,12] . Farmers generally rely on repeated applications of chemical fungicides to manage Phytophthora blight; however, exclusive reliance on chemicals often results in inconsistent disease control due to the soil-borne nature of the pathogen, higher production costs, and environmental concerns (Sharma et al., 2016; Singh et al., 2020) [15,16] . In this context, Integrated Disease Management (IDM), which integrates biological control agents, cultural practices, and need-based fungicide application, has emerged as a more effective and sustainable approach for managing soil-borne diseases in pulse crops (Pande et al., 2011; Ghosh et al., 2021) [4,11] . [6,2,10] . Therefore, the present study was conducted to evaluate the effectiveness of an IDM module for managing Phytophthora blight of pigeonpea under farmers' field conditions.

Materials and Methods Experimental Site and Farming Situation

The on-farm trials were conducted during the kharif seasons of 2022-23 and 2023-24 at Uplai (Khurd) and Uplai (Budruk), Ta. Madha, in Solapur district, Maharashtra. The region has a semi-arid climate with erratic rainfall. The trials were conducted under rainfed conditions, where temporary waterlogging is common during periods of heavy rainfall, creating favourable conditions for Phytophthora blight.

Experimental Design and Treatments

A total of 15 on-farm trials were conducted in farmers' fields following standard KVK methodology. Two treatments were evaluated:  T1: Farmers Practice (FP) Spraying of Thiophanate methyl  T2: Integrated Disease Management (IDM) 1. Seed treatment with Trichoderma @ 5 g kg⁻¹ seed 2. Two foliar sprays of Metalaxyl 4% + Mancozeb 64% @ 1.5 g l⁻¹ at 15-day intervals, starting from 15 days after germination

The technology was sourced from the Indian Institute of Pulses Research (IIPR), Kanpur.

Observations Recorded

The following observations were recorded:  Percent disease incidence (PDI)  Grain yield (q ha⁻¹)  Benefit-cost ratio (BCR)

Disease incidence was calculated based on the number of infected plants in the field. Yield data were recorded at harvest. Economic analysis was conducted using prevailing market prices.

Statistical Analysis: Data collected over two years were pooled and analysed statistically. Critical difference (CD) at the 5% level and coefficient of variation (CV) were computed to assess the significance of treatment effects.

Results and Discussion Effect on Phytophthora Blight Incidence

The integrated disease management module significantly reduced Phytophthora blight incidence compared with farmers' practice in both years of experimentation (Table 1) and Fig 1234). The pooled mean disease incidence under IDM treatment was 8.8%, whereas farmers' practice recorded a higher incidence of 22.8%, resulting in a 61.4% reduction compared with farmers' practice.

The reduction in disease incidence under the IDM module may be attributed to the combined effect of biological and chemical components. Seed treatment with Trichoderma suppresses soil-borne pathogens through mechanisms such as competition, mycoparasitism, and antibiosis, thereby reducing initial inoculum levels (Harman et al., 2004) [6] . Similar reductions in Phytophthora blight incidence have been reported earlier in pigeonpea through integrated approaches (Sharma et al., 2012; Pande et al., 2011) [13,11] .

Effect on Yield: Effective disease management under the IDM module led to a significant increase in yield. The pooled mean yield under IDM treatment was 20.6 q ha⁻¹, compared with 16.4 q ha⁻¹ under farmers' practice. Improved crop stand and reduced plant mortality under IDM treatment contributed to higher yields. Earlier researchers working on integrated disease management of pulse crops have also reported a positive association between reduced disease incidence and increased yield (Pande et al., 2011) [11] . Effective suppression of Phytophthora blight improves nutrient uptake and overall crop growth, thereby enhancing productivity.

Economic Analysis

The IDM module recorded a higher benefit-cost ratio (2.4) than farmers' practice (1.8), indicating better economic returns. Although the IDM treatment incurred additional input costs, the higher yield offset the investment, resulting in higher profitability. Similar economic benefits of IDM practices in pigeonpea have been documented earlier (Sharma et al., 2012; IIPR, 2016) [13,7] .

Conclusion

This study clearly shows that integrated disease management (IDM) is a proven, sustainable approach for controlling Phytophthora blight in pigeonpea grown under rainfed conditions. The IDM approach, which includes seed treatment with Trichoderma and two foliar sprays of Metalaxyl + Mancozeb, reduced disease incidence by 61.4% compared with farmers' usual practices. This effective disease control improved plant health, increased yield, and boosted economic returns.

The integrated approach produced higher yields and a better benefit-cost ratio than traditional practices, demonstrating its economic soundness. Implementing this IDM strategy can help reduce yield losses from Phytophthora blight and improve the productivity and profitability of pigeonpea in rainfed areas prone to disease.

Acknowledgement

AcknowledgementKrishi Vigyan Kendra, Mohol, Dist. Solapur, is grateful to the Director, ICAR-ATARI, Zone VIII, Pune, and the Director, Extension Education, MPKV, Rahuri, for their excellent technical, administrative, and financial support in conducting the OFT, and to the participating farmers for their cooperation in the successful conduct of the On-Farm Trials.

References

1. Directorate of Economics and Statistics, Maharashtra. Area, production and productivity of pulses in Maharashtra (2023-24). Mumbai: Government of Maharashtra; 2024.
2. Dubey SC, Tripathi A, Singh B. Integrated management of soil-borne diseases of pulses using Trichoderma species. Indian Phytopathology. 2020;73:607-618. DOI:10.1007/s42360-020-00265-4
3. Food and Agriculture Organization of the United Nations. FAOSTAT statistical database. Rome: FAO; 2023.
4. Ghosh R, Pande S, Sharma M. Integrated disease management strategies for soil-borne diseases of pulse crops. Legume Research. 2021;44(4):385-392. DOI:10.18805/LR-4251
5. Ghosh R, Sharma M, Telangre R, Pande S. Occurrence and distribution of Phytophthora blight of pigeonpea in India. Plant Disease. 2019;103(8):1966-1973. DOI:10.1094/PDIS-10-18-1713-RE
6. Harman GE, Howell CR, Viterbo A, Chet I, Lorito M. Trichoderma species opportunistic, avirulent plant symbionts. Nature Reviews Microbiology. 2004;2:4356. DOI:10.1038/nrmicro797
7. Indian Council of Agricultural Research -Indian Institute of Pulses Research. Annual report 2015-16. Kanpur: ICAR-IIPR; 2016.
8. Kannaiyan J, Nene YL, Reddy MV, Ryan JG, Raju TN. Prevalence of pigeonpea diseases and associated crop losses in India. Tropical Pest Management. 1984;30:6271. DOI:10.1080/09670878409370872
9. Meena RS, Singh A, Yadav RS. Role of bioagents in sustainable management of soil-borne diseases of pulses. Journal of Biological Control. 2022;36(3):145152.
10. Pande S, Sharma M, Ghosh R. Integrated disease management of pigeonpea diseases. Indian Journal of Plant Protection. 2011;39(3):168-176.
11. Pande S, Sharma M, Ghosh R, Rao JN. Yield loss assessment of Phytophthora blight in pigeonpea. Journal of SAT Agricultural Research. 2013;11:1-5.
12. Sharma M, Ghosh R, Pande S. Biology and management of Phytophthora blight of pigeonpea. Indian Phytopathology. 2012;65:111-120.
13. Sharma M, Ghosh R, Pande S. Climate change and emerging diseases of pulse crops. Indian Journal of Agricultural Sciences. 2015;85(9):1153-1161.
14. Sharma M, Ghosh R, Pande S. Fungicide use and resistance risk in management of soil-borne diseases of pulses. Indian Phytopathology. 2016;69:339-347.
15. Singh D, Kumar S, Singh AK. Fungicide resistance and its management in soil-borne pathogens of pulse crops. Plant Pathology Journal. 2020;36(2):89-98.