Common Tea Diseases and How to Manage Them

Tea (Camellia sinensis) is one of the world’s most widely consumed beverages and a critical cash crop across Asia, Africa, and South America. But behind every healthy flush of tea leaves is a constant battle against fungal pathogens. According to research published by Tezpur University, tea plantations are particularly vulnerable to disease because the crop is perennial, grown in monoculture, and thrives in warm, humid conditions – the exact environment that fungal pathogens prefer. Diseases affecting the roots, stems, and leaves of tea plants can reduce yield, lower quality, and in severe cases, destroy entire sections of a plantation. Understanding these diseases – and how to manage them – is essential for any tea grower.

Why tea plants are so vulnerable to disease 🔗

Fungal pathogens are the most significant biotic threat to tea production globally, affecting the foliage, stems, and roots. The dense canopy of a mature tea garden traps humidity, and the warm temperatures required for good growth also accelerate pathogen development and spore dispersal. Climate change has further intensified disease pressure in many growing regions. Tea diseases are broadly classified by the part of the plant they attack: roots, stems, and leaves – each category presenting distinct symptoms and management challenges.

Root diseases of tea 🔗

Root diseases are among the most destructive because they are often detected late – by the time above-ground symptoms appear, significant root damage has already occurred. They are classified as primary and secondary root diseases based on the vigour of the host plant they attack.

Black root rot 🔗

Black root rot is a primary root disease, meaning it can infect even healthy, well-established tea plants. The disease causes the roots to turn dark brown to black as the fungal infection progresses through the root tissues. Above-ground symptoms include gradual wilting of shoots, yellowing of leaves (chlorosis), and a general decline in plant vigour. In advanced cases, the entire plant may collapse. Research from IntechOpen’s tea disease diagnosis compendium documents this as one of several soil-borne fungal diseases that require early intervention for effective control.

Red root rot 🔗

Red root rot is another primary root disease that causes characteristic reddish discolouration on infected roots. Ganoderma species and related fungi have been documented as causative agents. The plant wilts progressively, and the root system shows the tell-tale red coloration that gives the disease its name. Like black root rot, the above-ground symptoms – including leaf chlorosis, reduced shoot growth, and eventual dieback – often mask the severity of what is happening underground.

Violet root rot – a secondary root disease 🔗

Unlike the primary root diseases above, violet root rot is a secondary disease, typically targeting plants already stressed by poor drainage, nutrient deficiency, or damage from other pathogens. The infected roots develop a characteristic violet or purple fungal coating caused by the growth of the pathogen on the root surface. Plants affected by violet root rot often show above-ground symptoms similar to other root diseases – wilting and yellowing – but the distinctive violet colouration of roots distinguishes it during field inspection. The University of Hawaii’s tea disease identification guide highlights that poorly drained sites and plant stress are key predisposing factors for secondary root infections like this one.

Controlling root diseases 🔗

Effective management of root diseases combines cultural and chemical approaches. On the cultural side, growers are advised to avoid poorly drained planting sites, remove all infected plant material (including roots of pencil-thickness or larger), and burn the collected debris to prevent re-infection. Growing non-host grasses such as Guatemala grass (Tripsacum laxum) for 18-24 months prior to planting is practised in India and Sri Lanka to reduce root rot inoculum in the soil. On the chemical side, nanocopper, carbendazim, and DMI fungicides such as hexaconazole are used to manage root rot pathogens. Research from the UPASI Tea Research Foundation recommends incorporating biocontrol agents like Trichoderma spp. and Gliocladium virens into planting pits as an additional layer of protection, with systemic fungicides such as hexaconazole found effective even at low concentrations.

Stem diseases of tea 🔗

Stem diseases attack the structural framework of the tea plant. They often enter through pruning wounds or mechanical damage, making post-pruning hygiene a critical element of disease prevention.

Collar canker 🔗

Collar canker is a fungal disease that develops at or near the base of the tea plant, at the soil line – the region known as the collar. It can be caused by Phomopsis theae or the Fusarium solani species complex, and is more prevalent in young tea, with clones showing greater susceptibility than seedlings. The disease begins with bark discolouration and the formation of sunken, dead lesions (cankers) near the plant base. As it progresses, the canker expands and gradually girdles the stem, cutting off the flow of water and nutrients to the upper plant. Plants may survive for a time with reduced vigour but eventually die once the canker completely encircles the stem. Studies at UPASI TRF found that soil type plays a significant role – disease incidence is higher in gravelly soils, and both chemical and biocontrol measures have been identified for management. Soil drenching with carbendazim has also shown effectiveness in reducing Phomopsis-caused cankers.

Wood rot 🔗

Wood rot fungi invade the internal woody tissues of tea stems and branches, causing structural decay that is often invisible until significant damage has occurred. Hypoxylon wood rot, caused by Nemania diffusa, is one of the documented forms in tea plantations. Pathogens enter through pruning cuts, mechanical wounds, or natural openings in the bark – which is why poor pruning practices that leave large unprotected cuts significantly raise infection risk. Research published in the Journal of Plantation Crops found that chemical fungicides (benomyl or copper oxychloride at 0.01%), botanical extracts, and biocontrol agents (Bacillus sp., Pseudomonas sp., and Trichoderma viride) were all effective against the wood rot pathogen under controlled conditions.

Managing stem diseases 🔗

The foundation of stem disease management is wound protection. All pruning cuts should be treated promptly with a suitable fungicidal paste or Bordeaux mixture to prevent pathogen entry. Diseased branches must be pruned out and removed from the field. Maintaining plant nutrition and avoiding unnecessary wounding reduces susceptibility. For established canker infections, soil drenching with systemic fungicides and integration of biocontrol agents are the recommended approach.

Leaf diseases of tea 🔗

Leaf diseases are the most economically significant diseases in tea because they directly attack the harvestable portion of the plant – the young shoots and tender leaves. They are also the most visually apparent and can spread rapidly under suitable weather conditions.

Blister blight 🔗

Blister blight, caused by the obligate biotrophic fungus Exobasidium vexans, is considered the most economically important leaf disease in tea plantations, occurring in nearly all tea-growing countries except those in Africa and the Americas. The pathogen infects young, harvestable tea shoots and causes approximately 40% yield loss. It also alters the biochemical composition of tea – including catechins, flavonoids, and phenols – directly compromising the quality of the final product.

Symptoms begin as small, pinhole-sized transparent spots on young leaves less than a month old. Over about seven days, these spots expand and develop into characteristic blister-like swellings on the lower leaf surface, surrounded by dark green, water-soaked zones. As the blisters mature, they become white and velvety following spore release, then turn brown. Infected young stems can bend, distort, and break off. The disease spreads fastest during cool, humid, cloudy conditions – particularly during the monsoon season.

For control, systemic fungicides hexaconazole, bitertanol, and propiconazole are the most effective recommendations, with a combination schedule of triazoles (hexaconazole, propiconazole) and morpholine fungicide (tridemorph) also in use. The efficacy of triazoles improves when used in combination with copper oxychloride. Cultural practices – including shade thinning at the onset of disease season and skiffing (removal of shoots at 2-3 inches above the plucking table) – are also practised to reduce inoculum.

Grey blight 🔗

Grey blight is caused by Pestalotiopsis spp. (also recently identified as Neopestalotiopsis clavispora in some regions). It is considered a weak pathogen that typically attacks tea plants already weakened by improper care or adverse environmental conditions – such as drought stress, pest damage, or nutritional deficiency. The disease is favoured by poor air circulation, high temperatures, and prolonged leaf wetness.

Symptoms appear as greyish-brown lesions that often start at the leaf margins and spread inward. A survey conducted across Southern India in 2022-2023 found grey blight incidence ranging from 11.41% to 57.02% across different tea-growing tracts, underscoring its widespread occurrence. Grey blight becomes most severe during the monsoon season when humidity remains elevated for extended periods and can cause significant defoliation if left unmanaged.

For management, carbendazim and thiophanate methyl are used for controlling grey blight in India. Copper oxychloride (0.25%) also provides effective control. Biocontrol agents such as Bacillus subtilis, B. amyloliquefaciens, and Pseudomonas fluorescens have achieved disease reduction comparable to synthetic fungicides in field trials, offering a promising sustainable alternative. Improving canopy air circulation through proper pruning and adequate plant spacing is a key cultural measure.

Integrated disease management – the way forward 🔗

No single approach is sufficient to manage tea diseases sustainably. Effective management of fungal diseases in tea requires a combination of good cultural and agronomic practices, targeted use of fungicides, microbial biocontrol agents, plant defense elicitors, and resistant cultivars. Copper oxychloride remains a widely used and versatile option for both leaf and stem diseases, providing both preventive and curative action. Hexaconazole, as a systemic fungicide absorbed into plant tissues, offers longer-lasting protection against multiple diseases. However, over-reliance on any single fungicide group risks the development of resistance – making rotation between fungicide groups and integration with cultural and biological controls essential for long-term effectiveness.

Cultural practices are the first line of defence: maintaining adequate plant spacing to allow air circulation, avoiding waterlogged sites, protecting pruning wounds, ensuring good plant nutrition, and promptly removing and destroying diseased material. These practices reduce pathogen pressure and create conditions that are less favourable to disease development across all three disease categories – roots, stems, and leaves.

What do you think? Given that blister blight alone can cause up to 40% crop loss, how important do you think it is for tea growers to invest in predictive disease forecasting tools before applying fungicides? And with biocontrol agents now showing results comparable to synthetic fungicides for grey blight and blister blight, do you think the tea industry is moving fast enough toward biological alternatives to protect both yield and human health?

References

1. https://www.intechopen.com/chapters/74600
2. https://apsjournals.apsnet.org/doi/10.1094/PDIS-09-20-1945-FE
3. https://www.intechopen.com/chapters/1160040
4. https://www.ctahr.hawaii.edu/oc/freepubs/pdf/PD-33.pdf
5. https://www.upasitearesearch.org/plant-pathology-microbiology/
6. https://www.slideshare.net/slideshow/diseases-of-tea/77076654
7. https://www.dhanuka.com/blogs/controlling-measures-for-blister-blight-in-tea-production
8. http://www.agriculturejournal.org/volume11number2/integrated-approach-to-management-of-brown-root-rot-disease-of-tea-camellia-sinensis-lo-kuntze/
9. https://www.sciencedirect.com/science/article/abs/pii/S0261219424004125