Status of chilli powdery mildew in major cultivation zones of Telangana

Introduction

Chilli (Capsicum annuum L.) is one of the most economically important spice crops grown globally, valued not only for its culinary uses but also for its pharmaceutical and industrial applications. India is the largest producer, consumer, and exporter of chilli, accounting for nearly 36% of global production (FAO, 2022) [2] . Telangana, Andhra Pradesh, Karnataka, and Madhya Pradesh are the leading chilli-growing states in India, with Telangana contributing significantly to both domestic markets and exports (Kumar et al., 2020) [7] . The crop's commercial success is, however, hampered by several abiotic stresses and devastating diseases. Among foliar diseases, powdery mildew caused by Leveillula taurica (Lév.) Arn. is of major concern. This obligate biotrophic pathogen, belonging to the family Erysiphaceae, has a broad host range infecting solanaceous crops such as chilli, tomato, and brinjal (Pérez-García et al., 2009) [12] . Unlike most powdery mildew fungi that produce superficial hyphae, L. taurica exhibits an unusual infection biology, its hyphae colonize the mesophyll tissue, while sporulation occurs externally through stomata. This endophytic growth pattern not only complicates its diagnosis but also reduces the effectiveness of surface-applied fungicides (Bertrand, 2019) [1] . The disease typically appears as whitish powdery patches on the lower leaf surface, often accompanied by chlorotic or necrotic spots on the upper surface. Severe infections cause premature leaf drop, reduced photosynthesis, and poor fruit development, ultimately leading to yield losses of 30-50% depending on variety, climate, and management practices (Kamble et al., 2019; Singh et al., 2021) [6,16] . Environmental factors such as high temperatures, dry weather, and intermittent humidity strongly favor the pathogen's development (Patel et al., 2022) [10] . These conditions are prevalent in Telangana during the Rabi season, making chilli particularly vulnerable. The predominance of susceptible varieties such as 'Teja' further exacerbates the situation.

While sporadic reports on the occurrence of powdery mildew in chilli exist from Gujarat, Karnataka, and Andhra Pradesh (Reddy et al., 2018; Patel et al., 2022) [13,10] , systematic surveys across Telangana are scarce. Baseline data on disease distribution, severity, and varietal susceptibility are essential for designing integrated disease management (IDM) strategies, guiding resistant variety deployment, and forecasting disease outbreaks.

Therefore, the present investigation was conducted to study the severity and distribution of powdery mildew in major chilli-growing districts of Telangana during Rabi 2024-25.

Materials and Methods

An intensive roving survey was carried out during Rabi 2024-25 in the major chilli-growing districts of Telangana, namely Gadwal, Warangal, Nalgonda, Suryapet, and Khammam. These districts were selected based on their large cultivation area, predominance of commercial varieties, and farmers' reports of powdery mildew occurrence. The survey was conducted between November and December 2024, coinciding with the flowering to fruiting stage of the crop, a period known to be highly conducive for powdery mildew development (Kamble et al., 2019; Singh et al., 2021) [6,16] . In each district, three mandals were selected, and in each mandal, three representative villages were surveyed. Within each village, three farmers' fields were assessed. From each field, four quadrants of 1 m² area (approximately 10 randomly selected plants) were observed to record disease severity. This hierarchical sampling ensured adequate representation of the variability in disease occurrence across agro-ecological conditions (Reddy et al., 2018; Patel et al., 2022) [13,10] .

Disease Assessment

Powdery mildew severity was scored visually on a 0-9 scale (Table 1) developed by Mayee and Datar (1986) [9] . The Per cent Disease Index (PDI) was calculated using the formula proposed by Wheeler (1969) [18]: PDI= (Sum of numerical ratings)/{Total number of observations × Maximum rating scale}×100

Table 1: Disease severity scoring scale for powdery mildew of chilli (Mayee and Datar, 1986) [9] Grade Description 0

No symptom of powdery mildew. 1

Small scattered powdery mildew specks covering 1% or less leaf area. 3

Small powdery lesions covering 1-10% of leaf area 5

Powdery lesions enlarged covering 11-25% of leaf area. 7

Powdery lesions coalesce to form big patches covering 26-50% of leaf area. 9

Big powdery patches covering 51% or more of leaf area and defoliation occurs.

GPS and Agro ecological data collection

The geographical coordinates (latitude and longitude) of each surveyed field were recorded using a handheld Global Positioning System (GPS) device to map disease distribution. Additional information such as variety grown, soil type and crop stage was collected through farmer interviews and field observations. Recording these parameters facilitated correlation analysis between environmental and varietal factors with disease severity (Pérez-García et al., 2009) [12] .

Statistical analysis

District-wise mean PDI, range, standard error (SE), and coefficient of variation (CV) were computed to assess variability in disease distribution. The mean PDI values were arcsine transformed prior to statistical analysis to stabilize variance (Gomez and Gomez, 1984) [5] . Microsoft Excel and SPSS statistical packages were used for data analysis.

Results

District wise severity of powdery mildew

Discussion

The present roving survey clearly demonstrated that chilli powdery mildew caused by L. taurica is widespread in Telangana, with disease severity varying significantly across districts, mandals, and villages. The overall mean PDI of 44.48% indicates moderate to high disease pressure during Rabi 2024-25. Among districts, Gadwal recorded the highest mean severity (66.85%), while Suryapet exhibited the lowest (33.45%). Such variability is consistent with earlier studies that reported regional differences in powdery mildew severity depending on varietal susceptibility, soil type, and microclimatic conditions (Reddy et al., 2018; Patel et al., 2022) [13,10] . The present findings are in line with earlier reports where powdery mildew caused yield losses of 14-30% in chilli (Gohokar and Peshney, 1981; Saroj and Satish, 1985) [4,14] . The wide variability observed in Telangana supports the view that powdery mildew epidemics are location-and season-specific, depending on varietal susceptibility and weather conditions (Geetha et al., 2017) [3] . Similar survey-based assessments in Andhra Pradesh and Karnataka have also indicated Gadwal-type regions as hot-spots for the pathogen (Udit Joshi et al., 2021) [17] . Recent studies have highlighted that high humidity (>70%) and temperatures between 20-28°C are strongly correlated with rapid development of Leveillula taurica, leading to epidemic outbreaks (Patil and Gopal, 2022) [11] . Early sowing combined with wider spacing has been reported to reduce disease incidence significantly by lowering canopy humidity (Kumar et al., 2023) [8] . Moreover, resistant cultivars such as US-1081 and Byadgi kaddi have consistently shown lower disease severity under epiphytotic conditions, confirming their potential for integrated management (Sharma and Singh, 2023) [15] . Fields dominated by the commercial cultivar 'Teja' consistently showed higher disease severity across districts, especially in Gadwal and Khammam. This supports earlier reports that 'Teja' is highly susceptible to L. taurica (Kamble et al., 2019) [6] . In contrast, varieties such as 'Byadgi Kaddi' and 'US 1081' exhibited relatively lower PDI, suggesting partial tolerance. Such findings underscore the critical role of varietal resistance in disease epidemiology (Singh et al., 2021) [16] . Furthermore, higher severity in red soils compared to black soils in some villages suggests that soil type and associated microclimatic conditions may influence disease expression, although this requires further experimental validation. Powdery mildew development is favored by warm, dry climates with intermittent humidity (Pérez-García et al., 2009) [12] . The Rabi season in Telangana provides exactly such conditions, which likely contributed to the high severity observed in Gadwal and Khammam. The low coefficient of variation (6.39%) in Gadwal indicates uniform and widespread infection, reflecting conducive environmental conditions coupled with cultivation of a single susceptible variety. By contrast, higher CV values in Nalgonda (36.92%) and Suryapet (27.43%) highlight localized outbreaks, possibly linked to variation in cropping systems, varietal diversity, and microclimate. The overall PDI (44.48%) observed in Telangana aligns with reports from Andhra Pradesh (Reddy et al., 2018) [13] , where mean severity ranged between 35-55%. Similarly, Patel et al. (2022) [10] reported severity levels of 30-60% in chilli growing tracts of Gujarat. These parallels confirm the adaptability of L. taurica across diverse agro-ecological zones of India. Pérez-García et al. (2009) [12] also highlighted the pathogen's ability to persist under a wide range of environmental conditions due to its unique endophytic growth.

Conclusion

The survey has clearly identified Gadwal and Khammam districts as critical zones with uniformly high disease pressure, while Nalgonda and Suryapet exhibited heterogeneous severity. The observed CV and SE values confirm the adequacy of the survey design, and the results provide a baseline for targeted disease management, varietal screening, and forecasting models in Telangana.

Acknowledgement

AcknowledgmentsThis study was part of Ph.D. Thesis of the first author and we express our sincere gratitude to the department of Plant Pathology, School of Agricultural Sciences, Malla Reddy University, Hyderabad, Telangana for their invaluable technical support.

References

1. Bertrand F. Endophytic growth and epidemiological significance of Leveillula taurica on solanaceous crops. Plant Pathol J. 2019;35(4):367-75.
2. FAO. FAOSTAT statistical database. Food and Agriculture Organization of the United Nations. 2022. Available from: http://www.fao.org/faostat/
3. Geetha R, Selvarani K. A study of chilli production and export from India. Int J Adv Res Innov Ideas Educ. 2017;3:2395-4396.
4. Gohokar RT, Peshney NL. Chemical control of powdery mildew of chilli. Indian J Agric Res. 1981;51:663-5.
5. Gomez KA, Gomez AA. Statistical procedures for agricultural research. 2nd ed. New York: John Wiley & Sons; 1984.
6. Kamble SS, Ghosh A, Patil RK. Epidemiology and management of powdery mildew in chilli. J Mycol Plant Pathol. 2019;49(3):250-256.
7. Kumar V, Rani S, Yadav MK. Chilli production in India: Status, challenges and opportunities. Indian J Agric Sci. 2020;90(12):2381-2387.
8. Kumar R, Singh M, Patel V. Integrated management of chilli powdery mildew: Current status and future prospects. Crop Prot. 2023;170:106846.
9. Mayee CD, Datar VV. Phytopathometry. Technical Bulletin-1. Parbhani: Marathwada Agricultural University; 1986.
10. Patel HR, Choudhary S, Patel RH. Survey and assessment of powdery mildew of chilli in Gujarat. Int J Plant Prot. 2022;15(2):100-5.
11. Patil SS, Gopal K. Impact of climate variables on powdery mildew epidemics in solanaceous crops. Plant Pathol J. 2022;38(4):567-75.
12. Pérez-García A, Romero D, Fernández-Ortuño D, López-Ruiz F, De Vicente A, Torés JA. The powdery mildew fungus Leveillula taurica: A unique biotroph. Adv Bot Res. 2009;51:1-30.
13. Reddy PN, Rao MS, Devi KS. Distribution and incidence of powdery mildew of chilli in Andhra Pradesh. Indian Phytopathol. 2018;71(1):123-6.
14. Saroj S, Satish L. Varietal reaction and evaluation of fungicides in vitro and in vivo against powdery mildew of chilli. Indian J Agric Res. 1985;55:85-7.
15. Sharma P, Singh R. Evaluation of fungicides against Leveillula taurica under field conditions. Indian Phytopathol. 2023;76:312-31.
16. Singh R, Sharma V, Gupta S. Powdery mildew of chilli: Epidemiology and management. Crop Prot. 2021;147:105688.
17. Udit J, Rana DK, Vivek S, Rajendra B. Morphological characterization of chilli (Capsicum annuum L.) genotypes. Appl Innov Res. 2023;2:231-6.
18. Wheeler BEJ. An introduction to plant diseases. London: John Wiley & Sons Ltd.; 1969.