Introduction
South India has been playing a major role in the global tea production. We have developed many control measures against blister blight disease in tea plantation. Since 1963, nickel, copper, sulphur and other formulations have been recomemended against blister blight disease. After the discovery of the first fungicide (Bordeaux mixture), usage of copper fungicides in plantation crops is being done to a maximum extent and very little synthetic organic fungicides has been utilized. One important concept developed during the 70s is the interaction of fungicides possessing different modes of action against specific pathogens. For instance, calixin has shown a very powerful antisporulant activity against blister blight disease (Venkata Ram, 1974), in addition to manifesting eradicative control through systemic action. The use of calixin in an integrated spray schedule (Venkata Ram and Chandra Mouli, 1976) has been recommended for preventing inoculums buildup, when this systemic organic formulation is likely to be more efficacious, i.e., just prior to be and after the heavy south west monsoon period; during the wet season, the combination of copper fungicide and nickel chloride has been advised for both protective and eradicative control. The results recorded from integrated control schedule were impressive as the yield was much superior in the control as compared to that of the Bordeaux sprays applied.
 
Plant protection programs and its application
Integrated fungicide spray application schedules continued to be developed in the 80’s and no doubt these improved the results of combined plant protection against disease and pest problems. Potentiating fungicides by using antibiotics is another area that holds promise in the development. Incorporation of mixture comprising streptomycin and tetracycline with copper oxychloride has shown to improve blister blight control of tea, with less usage of copper fungicide (Chandra Mouli and Venkata Ram, 1979). No great progress has been made in the development of soil fumigants in the 80’s. In tea industry, primary root disease pathogens such as Poria and Fomes, have been effectively eradicated by soil fumigation. Soil fumigation with methyl bromide has been extensively carried out for the control of fungal pathogens (Venkata Ram and Joseph, 1974). The plant protection equipments were also developed in the 80’s. The performance and efficiency of hand operated dusters, and sprayers were continued to improve the current decade, making chemical treatment against pest and diseases increasingly effective. There has been a very substantial improvement in the performance of motorized air – blast spraying equipment from the 60’s to the 70’s. For the tremendous research and valuable contributions of late Dr. C.S. Venkata Ram, he is commemorated every year in the form of the annual tea colloquim organized by UPASI. He is celebrated as a very strong role model for young tea researchers through his own research life and career. The inspiration from him draws every researcher to give his energy and contributions to the betterment of tea research. His research has been the building base of every research conducted in the division. He glittered in the UPASI as its former Plant Pathologist & Director. It is a privilege for Pathology division for his tremendous research in tea diseases and management which has saved the south Indian tea plantations from extinction.
 
Plant Pathology and Microbiology research activities
In Plant Pathology division, research is done on diseases of tea and their management. Blister blight is the most important foliar disease of tea. Extensive research has been carried out on the pathogen’s life cycle, epidemiology and control measures. It is a credit to the division that the timely control measures developed in the fifties saved the south Indian tea plantations from being wiped out by this disease. Based on the epidemiological studies, a computerized model has been developed for predicting the incidence of blister blight disease. So far, several fungicides have been screened against the disease, and the efficient ones were identified and recommended for use. Studies are under way to find out alternatives for chemical control measures and biological control strategy is one among them. Importance is also being given to the studies on resistance of plants to this pathogen. Studies on systemic acquired resistance (SAR) and induced systemic resistance (ISR) are being carried out. Understanding the biochemical and molecular basis of resistance can bring out effective strategies for disease control in future and already research work has been initiated. Forecasting model was developed for controling   blister blight disease of tea (Premkumar et al.,2002). Extensive research has been done on grey blight and brown blight diseases, which are other important foliar diseases of tea. After screening several fungicides, the effective ones have been recommended for field application. Recently, a number of bacterial and fungal strains have also been identified which antagonize the grey blight pathogen and also reported as new foliar fungal diseases (Cylindrocladium sp. and Alternaria alternata).

Wood rot and Branch canker are important stem diseases of tea in southern Indian tea plantations. Almost the entire population of old Assam seedlings is affected by these diseases which resulted in yield stagnation. Both the pathogens are wound pathogens and they gain entry through the wounds present in the tea bushes mostly sunscald injuries. Selective surgery and protection of wounds by applying copper oxychloride paste was the common practice followed in the control of stem diseases. Recently, this practice has failed due to copper oxychloride deleted from the list of approved chemical in tea plant. In this scenario, biological control integrated with chemical control of plant pathogens have been considered as potential control strategy in recent years. Native bacterial bio control agents were isolated from tea ecosystem and checked for their bio efficacy against wood rot and branch canker diseases under in vitro and in vivo. Proven strains (ten strains) were made in to a consortium which was found to be effective against wood rot and branch canker diseases. The consortium is very much compatible with agrochemicals. The consortium is commercialized and the marketing rights have been given to a commercial laboratory (TARI organic tea special). The influence of the climatic factors on the severity of the wood rot disease was critically assessed at monthly interval under field conditions. High ascospore production of Hypoxylon serpens occurred during monsoon period. Low sporulation occurred during the dry condition. Temperature ranged between 10 to 30o C with a relative humidity of above 60%. Monthly rainfall of 100-400 mm and an average sunshine hour of 2-4, favoured wood rot fungal spores. Collar canker disease caused by the fungus Phomopsis theae is a problem in young tea and comprehensive studies were carried out and effective control measures, both chemical and biocontrol, were identified.

Alternatives to the conventionally used soil fumigants for tea root disease control have been recommended to the industry. Systemic fungicides like hexaconazole was found effective and incorporation of biocontrol agents like Trichoderma sp. and Gliocladium virens in the planting pits prevented the occurrence of root disease. In biofertilizer research, several efficient strains of nitrogen fixing Azospirillum and Phosphobacteria and potassium solubilizing microor- ganisms have been isolated from tea soils of different tea districts. Critical research is underway on root diseases of tea and control measures through chemical/botanical/biological as integrated schedule then epidemiological aspects are underway. A user friendly microbial detection kit was developed which could be used in tea factories. Importance of a mill sanitizer, sanitrol in reducing microbial load in tea factories was proved. Signed memorandum of understanding with Multiplex and TARI organic tea special for commercialization of nitrogen fixers, Phosphobacteria strains and biocontrol agents to benefits of tea industry.
 
Tea factory hygiene
Factory hygiene is important for improving the quality of made tea. The nutrient rich tea juice and the crushed leaf bits adhering on to the machinery become a source of microbial contamination. The microbial load on the machinery gradually increases during the course of manufacture. Bacterial growth on the machinery if exceeds certain limits were adversely affect the quality of made tea (Baby and Sivakumar, 2006). The department has developed a user friendly kit for the quantitative analysis of microbial load present in the factory machinery and the kit is available for sale. Importance of a mill sanitizer, sanitrol in reducing microbial load in tea factories was proved.
 
Bioremediation in tea ecosystem
The therapeutic and nutritional value of tea has been well recognized and it is considered as a health drink in today’s context. It is indeed desirable to keep this drink completely free from agrochemical residues. Indiscriminate use of these agrochemicals results in leaching, pollution of ground water and top soil. Bioremediation is a process where biological organisms overcome environmental hazards resulting from accumulation of lethal chemicals or other hazardous wastes. Bioremediation is becoming gradually more adaptable due to its ecofriendliness and is one of the most cost effective methods compared to physical and chemical remediation processes. The organisms which are capable of remediating agrochemicals in the soil provide good environment to other beneficial microbes meanwhile eliminating harmful pathogens.

Integrated Pest and Disease Management (IPDM)
At present, pesticide residues in food cause serious concern globally. Usage of most of commonly use pesticide residues are restricted and plant protection code (PPC) has come that only a few agrochemicals are allowed to be used in the field for the management of pests and diseases in tea (www.teaboard.gov.in). Continuous use of synthetic chemicals for the control, may lead to development of resistance in targeted organisms. Development of integrated pest and disease management strategies adapting use of biologicals, enhancement of efficacy of biological control agents including entomopathogens, development of kairomone / pheromone traps and also non synthetic pesticides were definitely helpful in reducing the usage of synthetic insecticides for the control of tea pest in conventional tea fields also. The usage of microbial biocontrol agents proved to be an effective and alternative to obviate the deficiencies realized through the exclusive reliance on chemicals. Utilization of efficient native strains of all these antagonistic thus help us to combat tea diseases in an eco friendly manner. Conventionally, foliar diseases are controlled by systemic and contact fungicides in tea plantations. Further, public awareness on the pollution problems caused by fungicides and their failure due to resistance build up stressed the need for developing integrated disease management strategies through the integration of cultural, biological and judicious application of fungicides. This measure is eco-friendly and towards sustainable agriculture for the implement of IDM technology against tea diseases. Major contributions in the management of tea diseases have come up during the past several decades in disease management which have revealed the efficacy of biocontrol agents like Trichoderma and Gliocladium with suboptimal level of fungicides in controlling stem diseases like collar canker (Ponmurugan and Baby, 2007), thorny stem blight (Chandramouli and Baby, 2002), red root (Baby et al., 2004) and wood rot disease (Nepolean et al., 2014). The potential of phylloplane bacteria in controlling blister blight disease has also been reported (Baby et al., 2004) in tea plantations for implementation of IDM technology.

Surveys were undertaken in different tea growing zones of southern India for collecting diseased specimens and beneficial microorganisms. The indigenous wood rot and branch canker causal organisms were identified through molecular tools. A total of 645 bacterial and 40 fungal strains were isolated. The isolated bacterial and fungal biocontrol agents were screened for their antagonism against tea pathogens. Efficient strains have been identified as Bacillus sp. (WR46-2 & HBCWR-3), Pseudomonas sp. (WR5-4), Bacillus sp. (AGBB21), Alcaligenes faecalis (MBC-8, MBCP-7, WRP-4, WRPV-4), Bacillus weihenstep- hanensis (MBC-2), Brevundimonas diminuta (VPFWB) and Pseudomonas geniculata (WRPV5) through molecular techniques. An in vitro the study was carried out on growth inhibition of pathogens using several chemical fungicides and plant extracts. Proven biocontrol agents and plant extract of Artemisia nilagirica were sent to the Indian Institute of Crop Protection (IICPT) in order to identify their bioactive compounds which inhibit the growth of tea pathogens using GC-MS analysis. Based on molecular confirmation studies, the indigenous brown blight pathogen was isolated and identified as Glomerella cingulata in tea collected from south Indian tea plantations. The Endomopathogenic fungus (Beauveria bassiana) was isolated from infected tea mosquito. Proven strains of four actinomycetes were isolated and identified as Streptomyces crystallinus (APSA1), Streptomyces flavogriseus (AAS7), Streptomyces albus (CAS4) and Streptomyces xanthocidicus (APSA4) from tea soils. Three bacterial biocontrol agents were identified as Pseudomonas fluorescens, Bacillus amyloliquefaciens and Bacillus subtilis against branch canker pathogen. Plant aqueous extracts of Allamanda cathartica, Psidium guajava, Acorus calamus, Azardirachta indica, Curcumma longa, Murayya koenigii and Carica papaya were also tested at 5, 10 and 15% against branch canker pathogen. Leaf powder of Acorus calamus even at the lower dose (5%) inhibited the growth of branch canker fungus followed by Curcumma longa, Murayya koenigii, Azardirachta indica and Psidium guajava. Compatibility studies of bacterial and fungal biocontrol agents with various agrochemicals used in tea were completed. Studies on mass multiplication of biocontrol agents were carried out. Three days old liquid bacterial biocontrol culture (LB) and five days old fungal biocontrol culture (PDB) were mixed with sterile talc powder separately, which was suitable for field application. Straight application of Pseudomonas sp., Trichoderma sp. and consortium of Bacillus sp and Pseudomonas sp. provided good control of grey blight disease under field condition. While considering the integrated approach, the combination of Pseudomonas sp. and Bacillus sp. (5 kg/ha.) with recommended chemical fungicides (half dosages) efficiently controlled grey blight disease with 50% reduction in use of chemical fungicides. In the pruned fields, combined application of Bacillus sp. (100g / bush) with recommended chemical fungicides at 0.5% as wound pasting (1:1 ratio) were effective for integrated management of wood rot and branch canker diseases. Such integrated schedules did not affect the quality of made tea manufactured from leaf samples of treated plots. This study strengthens the concept of integrated management of grey blight, wood rot and branch canker diseases in tea. Efficient biocontrol agents are being maintained in germplasm of UPASI TRF, TRI Valparai. Proven bio control agents were also commercialized for implementation of integrated disease management (IDM technology) in tea.
 
Integrated Nutrient Management (INM) and its application:
Complete elimination of inorganic fertilizer is not possible in tea plantations. Integrated nutrient management, in which diverse sources of nutrients are harmoniously mixed, can meet the nutrient requirements to a large extent. In tea, the concept of manuring is based on replacement theory i.e., what is removed from soil by the plant during its growth is given back to soil, thus maintaining the level of these nutrients in the soil. The sources of organic matter in tea fields are tea pruning, shade tree litters, loppings and weeds. Due to the over use of chemical fertilizer the health of tea soils are affected in terms of soil enzymes. To prevent this, it is essential to reduce the use of chemical fertilizers. Due to the high fertilizer requirement, chemical fertilizer cannot be totally eliminated from the tea husbandry. Adoption of sound cultural practices will be helpful in maintaining or enriching the organic matter status of the soil. It will help in reducing the excess dependence on inorganic fertilizers and in the efficient utilization of applied fertilizers. Integrated nutrient management with biofertilizers will help to reduce the usage of chemical fertilizers without adversely affecting the production. The work in this direction assumes significance for improving the soil health and to sustain higher productivity of tea.

The results of the seedling nursery experiment indicated that application of biofertilizer with 50% reduction in inorganic fertilizers registered desired growth parameters. This can be adopted in nursery conditions instead of using 100% of IOF, which is practiced all three years. Results also indicated that integration of biofertilizer along with IOF can reduce the cost where 100% IOF application is expected. According to the soil biota, incorporation of bioinoculants enhanced the soil microflora thereby the soil health has been improved. Application of bioinoculants alone may found on par with growth characteristics of nursery grown control plants, but considering soil health, bioinoculants alone keep the soils “FERTILE” in terms of soil microflora. New plantation INM trial showed higher biomass productivity in 50% and 75% IOF combination with bioinoculants treatment next to 100% IOF. But this trial must be continued for confirming the efficiency of those treatments.

The nutrients required by crop plants are generally supplied through chemical fertilizers. However, continual use of agrochemicals may adversely affect soil productivity. Excessive use of inorganic also results in environmental and ground water pollution. Use of Biofertilizers becomes essential at this juncture to maintain soil productivity and to supply nutrients to the plants in an eco-friendly manner. Integrated Nutrient Management involves the use of organic manures, bio fertilizers with a view to reduce the quantity of inorganic sources of nutrients without affecting productivity. Bio fertilizers such as Azospirillum brasilense (Nitrogen fixer), Phosphate and potash solubilizing bacteria (Pseudomonas putida & Burkholderia cepacia) and VAM (Vesicular Arbuscular Mycorrhizae – mineral mobilizer) are extensively used to make available more quantity of nutrients to the plants so as to increase the productivity with reduction in the use of inorganic fertilizers. In this connection, UPASI TRF has conducted a series of trials and based on the results, it was found out that, by incorporating Biofertilizers the quantity of chemical fertilizers can be reduced by 50%. The efficient strains have been commecialized and available in the market under the brand name Biodyn –N (Azospirillum) and Biodyne–P (Phosphate solublizing bacteria) for commercialization to benefits of tea industry. The residue of manufactured tea and coffee was reclaimed to check their compatibility with Plant Growth Promoting Rhizobacteria and their shelf life was studied. The bioinoculants was compatible with the tested carrier materials like tea and coffee waste. On the shelf life observation, viability of PGPR was supported by tea waste and followed by coffee waste even after 120 days of incubation.
 
More research are underway for the new molecules and alternate recommendations are required for effective management of blister blight diseases using safer chemicals. Approaches are needed with field objectives to meet the increasing demand for an effective disease management in tea.
 
Acknowledgements
The authors are thankful to UPASI TRF & TRI, for providing the necessary facilities.

References
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