Over the weekend we celebrated International Tea Day (May 21st), a date set out by the United Nations to recognize the cultural importance of tea around the world and promote its sustainable production and consumption. Tea is the second most consumed beverage worldwide, after water, and serves an important 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, and 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.
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, the bud and first two to three leaves are hand-picked from a given tea plant and sent 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. Varying levels of oxidation alter the taste, color, and aroma, with black tea being the most oxidized and green tea being the least. Differences in tea quality are affected by the age of the leaf and the growing conditions, with young, light green leaves producing the highest quality tea.
Since tea is harvested all year round, the time between pesticide application and harvest is shorter than with other crops, making pesticide residues of especially high concern. Tea producers in India are feeling particularly pressured to move away from pesticides – as buyers last year rejected a series of tea shipments due to chemical residues being beyond acceptable limits. As a result, biological solutions are being ushered in.
Camellia sinensis requires warm and humid weather – conditions which are unfortunately also favored 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 acts by continually puncturing the leaf epidermis, sucking out the cell contents and leaving the leaves desiccated and void of chlorophyll. The CABI Portal CABI portal provides information for a variety of macrobial products that target this pest directly, such as the 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. Multiple bioproteski products are listed on the portal for thrips on tea, including an entomopathogenic fungus from the Lecanicillium genus, and parasitic nematodes from the Steinernema genus. Biological products are becoming not just a choice, but a necessity for crops like tea, where countries impose strict chemical residue limits upon entry.
That being said, not all tea-feeding insects are foes. India produces three main types of tea: Assam, Darjeeling, and Nilgiri. Darjeeling is a district in West Bengal where cultivation of the sinensis variety takes place to yield the black Darjeeling tea. The climate in this region creates four periods of cultivation referred to as “flushes”, each of which confers unique characteristics to the final product.
The first two flushes produce the most flavorful and sought-after tea. The second two flushes fall into monsoon season, and therefore undergo rapid growth, leading to a less developed flavor profile – these teas are often used for blending.
The first flush is in spring, where young, tender leaves are harvested to yield a gentle, light tea. The second flush is harvested in summer, after tea plants have been attacked by a leafhopper and moth species. Predatory attack causes the tea plant to release compounds that confer a full bodied, musky flavor to the tea, which is especially revered by connoisseurs.
This is an interesting case where insect-crop interactions lead to a desirable crop characteristic, further supporting the idea that insects should not be indiscriminately regarded as pests and approached with a broad-spectrum insecticide.
Tea means many things to many people – a vital source of income for a plantation worker, a medicinal beverage for someone seeking a cure, an everyday drink for dozens of cultures across the globe. Next time you fill up your cup, consider the non-traditional methods of pest control that help preserve the health of agricultural workers, consumers, and the environment. For more information, a good place to start is the CABI Portal CABI Portal, which boasts over 4,000 bioprotection products across 39 countries, as well as educational resources on biological pest management. Let’s better the backstory of that beverage that breathes life into us each morning!