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International Tea Day: how to fill our cups responsibly

Published 21/05/2023

Theme: Agriculture and bioprotection

The United Nations has set out May 21st as International Tea Day. It aims to recognize the cultural importance of tea globally and promote its sustainable production and consumption. Tea, the second most consumed beverage globally, plays a vital role in rural development, food security, and poverty reduction in developing countries.

The tea plant is native to East Asia, the Indian Subcontinent, and Southeast Asia. It was first cultivated in China as early as 5,000 years ago. Today, cultivation of tea occurs globally, in tropical and subtropical regions with the largest producers being China (2.97 million tonnes in 2020) and India (1.2 million tonnes in 2020). In celebration of this day, we will be discussing tea cultivation, common tea pests, and the bioprotection products available for managing them.

A woman harvesting tea leaves in India © Rajat Sarki via Unsplash

Origins of tea

For something to be considered tea, it must come from the tea plant Camellia sinensis. All types of tea commonly known today (white, yellow, green, oolong, black) are harvested from one of two major varieties of Camellia sinensis: var. sinensis and var. assamica. Every one to two weeks, workers hand-pick the bud and first two to three leaves from a given tea plant and send them for processing. It is the processing of the tea leaves, rather than the type of plant, that distinguishes different types of tea from one another. Oxidation is the process through which tea leaves are exposed to the air in order to dry and darken. Varying levels of oxidation alter the taste, color, and aroma, with black tea being the most oxidized and green tea being the least. The age of the leaf and the growing conditions affect differences in tea quality. Young, light green leaves produce the highest quality tea.

The fact that tea is harvested every few weeks throughout the year shortens the time between pesticide application and harvest compared to other crops. This makes pesticide residues of especially high concern. Tea producers in India have felt particularly high pressure to move away from pesticides as buyers last year rejected a series of tea shipments due to chemical residues being beyond acceptable limits (source). As a result, biological solutions are being ushered in.

Workers picking tea leaves in a plantation © Aboodi Vesakaran via Unsplash

Tea pests and bioprotection solutions

The climatic conditions required by Camellia sinensis (warm and humid) happen to be favoured by a diverse range of insects and diseases. Although caffeine, a secondary metabolite produced in C. sinensis, can deter some insects, it is not enough to keep all pests at bay. The red spider mite, Oligonychus coffeae, is among the foremost tea pests in India, and can cause up to 35-40% of crop losses. This pest punctures the leaf epidermis and sucks the cell contents, leaving the tea leaf desiccated and devoid of chlorophyll.

The CABI BioProtection Portal provides information for a variety of macrobial products that target this pest directly. These include predatory mites of the genus Amblyseius and predatory beetles from the genus Stethorus. Thrips are another notable tea pest, wreaking havoc by feeding on the underside of leaves with their piercing and sucking mouth parts. The Portal lists multiple bioprotection products for thrips on tea, including an entomopathogenic fungus from the Lecanicillium genus. It also features parasitic nematodes from the Steinernema genus. Biological products are essential for tea crops due to strict chemical residue limits imposed by countries.

Tea leaves with water droplets © Rashid via Unsplash

The importance of distinguishing between friend and foe

Not all tea-feeding insects are foes. India produces three main types of tea: Assam, Darjeeling, and Nilgiri. Darjeeling, West Bengal, cultivates sinensis variety for black Darjeeling tea, known for its distinctive flavor and unique characteristics. The climate in this region creates four cultivation periods, known as “flushes.” The leaves harvest during each flush impart unique characteristics to the final tea product. The first two flushes produce the most flavorful and sought-after tea. The second two flushes fall into the monsoon season, which leads them to undergo rapid growth and result in a less developed flavor profile. These leaves are often used in tea blends.

In spring, tea producers harvest young, tender leaves to yield a gentle, light tea during the first flush. Tea plants experience attacks by a leafhopper and moth species before harvesting the second flush in summer. Predatory attack triggers tea plants to release protective compounds that enhance flavors especially revered by connoisseurs for the full-bodied, musky taste they confer. This is an interesting case where insect-crop interactions lead to a desirable crop characteristic. It supports the idea that insects should not be indiscriminately regarded as pests and approached with a broad-spectrum insecticide.

A girl gathering tea leaves after harvest © Tsaiga via Unsplash

Tea holds diverse significance—a vital source of income, a medicinal beverage, and a daily ritual for various cultures worldwide. Next time you fill your cup, consider whether safe pest control methods were used in cultivation. Methods that protect the health of workers, consumers, and the environment, while preserving desirable tea characteristics conferred by certain ecological interactions. For more information, a good place to start is the CABI BioProtection Portal, which boasts over 4,000 bioprotection products across 39 countries and educational resources on biological pest management. Let’s better the backstory of that beverage that breathes life into us every morning! 

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