Abstract
Yellow Leaf Disease (YLD) poses a significant threat to arecanut cultivation, particularly in regions like Dakshina Kannada district, Karnataka, India. This study presents a comprehensive survey conducted across three taluks - Puttur, Bantwal, and Sullia to assess the incidence and intensity of YLD. In Puttur Taluk, disease incidence ranged widely from 0 to 100 percent, with Bajathoor and Savanur exhibiting the highest rates. Similar patterns were observed in disease intensity. Conversely, certain villages displayed no YLD intensity, suggesting potential areas for further investigation into disease resistance mechanisms. In Bantwal Taluk, varying levels of incidence and intensity were observed, emphasizing the localized nature of disease dynamics. In Sullia Taluk, a broad spectrum of vulnerability was noted, with Sampaje recording the highest incidence and intensity. However, several villages showed no observable disease incidence, indicating areas of resilience or effective management practices. Overall, the survey underscores the need for targeted interventions to mitigate YLD's impact on arecanut cultivation. These interventions should encompass cultural practices, chemical control measures, breeding for disease resistance, and integrated pest management. Additionally, capacity-building initiatives and farmer education programs are essential for enhancing awareness and adoption of best practices. Addressing the challenges posed by YLD requires a collaborative effort from all stakeholders, guided by scientific research and tailored to local farming communities' specific needs. Through collective action, the resilience of arecanut cultivation in Dakshina Kannada district and beyond can be ensured.
Introduction
Arecanut plays a vital role in cultural and social customs, especially in South and Southeast Asian countries like India, Bangladesh, Myanmar, Thailand and Indonesia. It is commonly offered as a gesture of hospitality, friendship, or respect during social gatherings, ceremonies, and religious rituals. It is often chewed along with betel leaf and slaked lime as a traditional stimulant, particularly in cultural and social contexts (Raghavan and Baruah, 1958). This practice, known as betel chewing, is deeply ingrained in the cultural fabric of many communities and is believed to have stimulant, digestive, and medicinal properties.
Arecanut cultivation is a significant source of livelihood for millions of farmers in regions where it is grown. The crop contributes substantially to the agricultural economy of countries like India, Indonesia, Sri Lanka, and Papua New Guinea. It provides employment opportunities not only in cultivation but also in processing, transportation, and marketing sectors. It is rich in nutrients and bioactive compounds. It contains carbohydrates, proteins, fats, vitamins (particularly vitamin E), and minerals like calcium, phosphorus, and iron. However, excessive consumption of arecanut, especially when chewed with other additives like tobacco, can lead to adverse health effects. However, its use in traditional medicine should be approached with caution due to potential health risks associated with excessive consumption. Industrial Uses: Apart from its traditional and cultural significance, arecanut finds applications in various industries. Its extracts are used in the manufacture of dyes, tannins and chemicals. Additionally, husks are utilized for making handicrafts, biofuels, and animal feed.
India is the largest producer and consumer of arecanut in the world, with a total area of 730.82 thousand ha and production of 1208.93 thousand tonnes and productivity of 1654 kg/ha. In Karnataka, 500 thousand ha of area is under arecanut cultivation and production of 950 thousand tonnes with productivity of 1900 kg/ha of nuts were produced during 2020-21 (DASD, 2021). Arecanut, being a major commercial crop in several tropical regions, is susceptible to various diseases that can adversely affect its growth, yield, and quality. Some of the common diseases of arecanut are Yellow Leaf Disease (Phytoplasma); Leaf spot and Inflorescence die back (Colletotrichum gleosporoides); Fruit Rot (Phytophthora arecae); Leaf Blight (Pestalotiopsis palmarum); Bud Rot (Phytophthora palmivora) and Foot rot (Ganoderma lucidum)
Yellow Leaf Disease (YLD) of arecanut is a significant concern in regions where arecanut cultivation is prominent, such as parts of India, including the Dakshina Kannada district in Karnataka (Hiremata et al., 2020). This disease was first reported by Nambiar, 1949, caused by various primarily by phytoplasma, manifests as yellowing of the leaves and leading to considerable yield losses if not managed effectively. Symptoms includes yellowing of leaves, often starts from the lower leaves and gradually progresses upwards. Infected leaves may exhibit yellowing along the margins or throughout the leaf surface, with veins retaining green color initially (Chowdappa et al., 1995). As the disease advances, affected leaves may dry up and drop prematurely, leading to defoliation and reduced crown region.
YLD is caused by phytoplasma (a type of bacteria-like organism). Transmission of the disease is primarily by insect vectors, plant hoppers (Proutista moesta). YLD significantly reduce the yield and quality of arecanut. Severe infections can lead to stunted growth, reduced nut size and decreased nut production, ultimately affecting the economic viability of arecanut cultivation. Managing Yellow Leaf Disease requires an integrated approach that combines cultural, chemical and biological control measures. These may include the use of disease-resistant varieties, regular monitoring and early detection of symptoms, pruning and removal of infected plant parts and adoption of good agricultural practices to minimize disease spread. Ongoing research and extension efforts are focused on understanding the severity and spread of disease from endemic regions to non-traditional areas. Collaboration between researchers, extension agents and farmers are essential for disseminating information for implementing effective disease management strategies. Keeping all these points in view, the study has been carried out and implemented.
Materials and Methods
An intensive roving survey was carried out during 2021-22 to assess the incidence and intensity of yellow leaf disease in major arecanut growing regions of Karnataka viz., Putturu, Bantwal and Sullia taluks of Chikkamagaluru district. At each location five fields were selected randomly and per cent disease incidence was calculated by observing twenty five plants per garden and the intensity was calculated by selecting five plants at each garden by following scoring system (Table 1a, 1b, 1c) given by George et al. (1980).
| Table 1a: Intensity of yellow leaf disease of arecanut - Scoring for yellowing (Y) | ||
|---|---|---|
| Sl. No. | Features | Scoring |
| 1 | Healthy | 0 |
| 2 | Tip yellowing upto 25 % of leaflets | 1 |
| 3 | Tip yellowing upto 50 % of leaflets | 2 |
| 4 | Tip yellowing more than 50 % + marginal yellowing upto 25 % | 3 |
| 5 | Tip yellowing in full + marginal yellowing upto 50 % + Complete yellowing upto 25 % | 4 |
| 6 | Tip yellowing in full + marginal yellowing upto more than 50 % + Complete yellowing upto 50 % | 5 |
| 7 | Tip yellowing in full + marginal yellowing upto more than 50 % + Complete yellowing in full (mild) | 6 |
| 8 | Complete yellowing in full (severe) | 7 |
| Table 1b: Intensity of yellow leaf disease of arecanut - Scoring for Necrosis (N) | ||
|---|---|---|
| Sl. No. | Features | Scoring |
| 1 | Healthy | 0 |
| 2 | Necrosis upto 50 % of the leaflets | 1 |
| 3 | Necrosis in more than 50% of the leaflets | 2 |
| Table 1c: Intensity of yellow leaf disease of arecanut - Scoring for Crow Size Reduction (R) | ||
|---|---|---|
| Sl. No. | Features | Scoring |
| 1 | Healthy | 0 |
| 2 | Reduction in size of younger leaves | 0.5 |
| 3 | Reduction in size of younger leaves and stem tapering | 1 |
Estimation of percent disease incidence
The percent disease incidence was assessed by recording the number of plants showing disease symptoms, out of the total number of plants examined.
Symptoms: Rawther (1976) recorded the characteristic symptoms of the disease as
- Inter-venial foliar yellowing starting from the tips of leaflets in two to three leaves of the outermost whorl (Y).
- Necrosis of the leaflets and eventually dry up (N).
- In advanced stage, leaves are reduced in size, become stiff and pointed, closely bunched and abnormally puckered (R).
Based on the standard symptoms observed during survey, percent disease incidence and intensity was calculated.
The percentage of disease incidence was calculated by using the following formula.
|
Disease Incidence (DI %) = |
Number of infected plants ___________________________ Total number of plants examined |
× 100 |
Assessment for the intensity of yellow leaf disease of arecanut
Mean of twenty-five plants were used to determine the intensity scoring by using formula given below by George et al. (1980).
Scoring system to assess intensity in yellow leaf affected gardens
Intensity = ((Y+N)/L+ R) × 10
Where,
- Y = Total scoring for yellowing of the leaves (0-7)
- N = Scoring for the necrosis of the leaves (0-2)
- R=Scoring for reduction in size of the crown (0-1)
- L = Half the number of leaves in the crown
Results and Discussion
Symptomology of the yellow leaf disease of arecanut
Symptom appearance and its presence on the plant can be seen across all the three seasons in a year. However, conspicuous symptoms of YLD were well pronounced immediately after the onset of South-West monsoon rains especially during August-November where, its cessation and maintaining of the green colour by the younger leaves is commonly observed in majority of gardens. Characteristics of yellowing starts from the tip of the leaflets of second or third fronds of the outer most whorls of the palm. Later on yellowing gradually extends to the middle of the lamina showing typical demarcation of yellow and green parallel bands on both sides of the midrib of the leaflets. The leaves become stiff and pointed, closely bunched and abnormally puckered. As the disease progresses, yellowing extends to the whole lamina and leaf tips become necrotic and dries up during summer leaving the leaf stalk green. Subsequently, symptoms appeared on both mature and immature nuts wherein, kernel size gets reduced, discoloration and rotting of kernels and non production of inflorescence and if produced, drying up of the entire inflorescence was also observed. At the advanced stage, crown size reduction, reduction in the inter nodal length and tapering of the stem followed by decapitation of the entire crown leaving a bare trunk were conspicuous. Affected plant roots also exhibit brown to black colour discoloration (Fig.1). By observing these symptoms, incidence and intensity of palms were calculated.
Fig. 1: Typical Symptoms of yellow leaf disease of Arecanut
Survey for the incidence and intensity of yellow leaf disease of arecanut in Chikkamagaluru district
Arecanut is a cornerstone of agriculture in Dakshina Kannada district, Karnataka, India. However, the cultivation of this economically significant crop faces substantial challenges due to various diseases, with Yellow Leaf Disease (YLD) being one of the most prevalent and detrimental.
Understanding the extent and severity of YLD across different taluks and districts is paramount for effective disease management and sustainable arecanut cultivation practices. This study presents the comprehensive findings of a survey conducted to assess YLD incidence and intensity in three taluks of Dakshina Kannada district was represented in Table 2.
In Puttur Taluk, the survey unveiled a wide spectrum of disease incidence, ranging from 0 to 100 percent, indicating varied vulnerability levels among different areas. Notably, Bajathoor exhibited the highest disease incidence at 100 percent, closely followed by Savanur at 95 percent. Concurrently, disease intensity exhibited a similar pattern, ranging from 0 to 97.50 percent, with Bajathoor recording the highest intensity at 97.50 percent, trailed closely by Savanur at 92.50 percent. Remarkably, certain villages such as Barike, Navoor, Nekkare, Kochhi, and Punchatharu displayed no intensity of YLD, signaling potential areas for further study on disease resistance mechanisms.
The survey in Bantwal Taluk uncovered disease incidence varying from 0 to 40.00 percent, with corresponding intensity levels ranging from 0 to 30.00 percent. Notably, Urimajalu emerged as the village with the highest disease incidence at 50.00 percent, closely followed by Ananthady at 40.00 percent. However, intensity levels displayed a different trend, with Urimajalu recording the highest intensity at 30.00 percent, followed by Ananthady at 27.50 percent. These findings underscore the localized nature of disease dynamics within the taluk and highlight the need for tailored management strategies.
In Sullia Taluk, disease incidence spanned from 0 to 100.00 percent, showcasing a broad spectrum of vulnerability across surveyed areas. Sampaje registered the highest disease incidence at 100.00 percent, accompanied by a significant intensity of 95.00 percent. Additionally, villages such as Panja, Alletti, and Guttigar exhibited a disease incidence of 95.00 percent, emphasizing the widespread nature of YLD within the taluk. Conversely, several villages including Yenekallu, Parla, Nadugallu, Balladi, Panjipalla, and Sannara displayed no observable disease incidence, suggesting potential areas of resilience or effective disease management practices.
Table 2: Prevalence and severity of yellow leaf disease across different areca nut plantations in Dakshina Kannada district
Conclusion
The findings of this survey shed light on the significant challenges posed by Yellow Leaf Disease (YLD) in arecanut cultivation across the taluks of Puttur, Bantwal, and Sullia in Dakshina Kannada district, Karnataka. The survey revealed a diverse landscape of YLD incidence and intensity across different areas within the surveyed taluks.
In Puttur Taluk, a wide spectrum of disease incidence ranging from 0 to 100 percent was observed, with Bajathoor and Savanur emerging as the areas with the highest incidence rates. Similarly, disease intensity exhibited a similar pattern, with Bajathoor and Savanur recording the highest intensities. Notably, certain villages displayed no intensity of YLD, indicating potential areas for further investigation into disease resistance mechanisms.
In Bantwal Taluk, the survey uncovered varying levels of disease incidence and intensity, highlighting the localized nature of disease dynamics within the taluk. Urimajalu and Ananthady emerged as the villages with the highest disease incidence, with intensity levels reflecting a different trend. These findings underscore the need for tailored management strategies to address the localized nature of YLD outbreaks.
In Sullia Taluk, the survey showcased a broad spectrum of vulnerability to YLD across surveyed areas. Sampaje recorded the highest disease incidence and intensity, emphasizing the widespread nature of YLD within the taluk. However, several villages displayed no observable disease incidence, suggesting potential areas of resilience or effective disease management practices.
Overall, the comprehensive findings of this survey underscore the importance of understanding the extent and severity of YLD for effective disease management and sustainable arecanut cultivation practices. By identifying areas of high vulnerability and localized disease hotspots, this study provides valuable insights for targeted interventions aimed at mitigating the impact of YLD on arecanut cultivation in Dakshina Kannada district. These strategies should encompass a combination of cultural practices, chemical control measures, breeding for disease resistance, and integrated pest management approaches. Additionally, capacity-building initiatives and farmer education programs are crucial for enhancing awareness and adoption of best practices to mitigate the impact of YLD and ensure the resilience of arecanut cultivation in the region. In conclusion, addressing the challenges posed by YLD requires a concerted effort from all stakeholders, guided by scientific research and tailored to the specific needs of the local farming communities. Through collective action and sustained commitment, we can safeguard the future of arecanut cultivation in Dakshina Kannada district and beyond.
The results indicate the probable association of various soil and environmental factors contributing for highest disease incidence in these districts. As the arecanut crop is cultivated from centuries its extensive cultivation especially in hilly tracts which receives an average annual rainfall of 3573 mm during South-West monsoon hastens the intensity of the disease to be endemic in nature. These results were in accordance with the results obtained by Krishnamurthy and Vajranabhaiah (2000) who reported the 24.4 to 40.00 per cent disease incidence in Sringeri and coastal zones (Sampaje belt) of Karnataka.
Conflict of interest
The authors have no conflict of interest.
References
Chowdappa, P., Balasimha, D., Rajagopal, V. and Ravindran, P. S. 1995. Stomatal responses in arecanut palms affected with yellow leaf disease. Journal of Plantation Crops, 23(2): 116-121.
DASD. 2021. https://www.dasd.gov.in/adminimage/Arecanut_area_and_production.pdf
George, M. V., Jacob, M. and Nagaraj, B. 1980. Indexing of the yellow leaf disease of arecanut. Journal of Plantation Crops, 8(1): 82-85.
Hiremata, V., Narayanaswamy, M., Narayanaswamy, H. and Satish, K. M. 2020. Survey for the assessment of arecanut yellow leaf disease (YLD) incidence in malnad region of Karnataka. International Journal of Environmental Science, 2(3): 326-328.
Krishnamurthy, K. and Vajranabhaiah, S. N. 2000. Arecanut-yellow leaf disease in Karnataka. Kisan world, 27: 57-59.
Nambiar, K. K. 1949. A Survey of arecanut Crop in Indian Union. Indian central arecanut committee, Calicut, pp. 74.
Raghavan, V. and Baruah, H. K. 1958. Arecanut: India’s popular masticatory-history, chemistry and utilization. Economic Botany, 12(4): 315-345.
Rawther, T. S. 1976. Yellow Leaf Disease of arecanut: symptomatology, bacterial and pathological studies. Arecanut and Spices Bulletin, 8: 22-24.
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