Coffe…uh, Tea Anyone?

Despite being a bit of a coffee geek (if you couldn’t already tell), I actually don’t drink the stuff at all ūüôā I definitely enjoy a cup of tea however, and I thought it might be interesting¬†to do a piece on the tea plant, Camellia sinensis. The plant itself is actually pruned to stay a smaller size, as if it were left to grow, it would blossom into a full sized-tree (unlike the coffee plant). Moreover, unlike coffee plants, tea plants are harvested for their leaves specifically, rendering their foliage to be their most valuable component.

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Currently, the largest producer of tea in the world is China, which produced over 1 million tonnes of tea in 2013. Despite the success, however, tea farmers and plantation owners in China are often subject to a variety of diseases, most of which can dramatically reduce production for the season. Today, we take a look at two pathogens, Exobasidium vexans and Exobasidium reticulatum, and how each affects the tea plant.

Exobasidium vexans

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One of the most notorious diseases in the tea industry, E. vexans is known for causing tea blister blights on the leaves of tea plants. In simple, the basidiospores (reproductive spores) of this fungus are extremely sensitive to light, and require a high level of humidity on the leaf of the plant to germinate. Due to these requirements, E. vexans often occurs at higher elevations (>700m), as well as in foggy and humid areas. According to research published by the Agricultural Academy of China, the number of infected shoots in a tea plantation is related directly to the density of basidiospores of the fungus in the air. The disease occurs every year from autumn to early spring, when basidiospore concentration is high (in the summer, spore concentrations are much lower). Several solutions have been used by owners of tea plantations to combat this fatal disease, including the application of nickel sulphate, as well as the use of the antibiotic polyoxin, which has been found to help stop the spread of the disease.

Exobasidium reticulatum

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Similar to E. vexans, E. reticulatum occurs on mature tea leaves, and often causes blister blights on the leaves of the tea plant. Growth conditions for the disease are also similar to E. vexans, as a high level of humidity on the plant leaf is ideal for germination. One point of difference, however, is the appearance of the blister blight on the leaf. While E. vexans appears on the leaf as large brown spots, E. reticulatum appears on the leaf in a white, dust-like pattern, similar to that of flour. As is the case with E. vexans, the severity of E. reticulatum depends on the concentration of basidiospores in the air, with a higher concentration leading to a larger number of plants being infected.

Final Thoughts

With tea representing the second most consumed beverage in the world, its no wonder as to why small scale setbacks can quickly turn into into large scale implications. Just like the coffee industry, the world largest suppliers often have a large amount of influence over the market, meaning that their plantation yields often determine the health and well-being of the industry as a whole.

Report by the Agricultural Academy of China: https://www.apsnet.org/publications/plantdisease/backissues/Documents/1982Articles/PlantDisease66n10_961.pdf

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