User:Iwillingly/Longan

Growth
Longan, alongside its sister fruit litchi, thrive in humid areas or places with high rainfall, and can grow on most types of soil that does not induce issues with water drainage. Ample temperatures are also instrumental in longan growth - while longan can resist small stretches of cool temperatures, they can be damaged or killed in longer stretches of temperatures as high as -2 degrees Celsius. Younger plants tend to be more vulnerable to the cold than those more mature.

Harvest
During harvest, pickers must climb ladders to carefully remove branches of fruit from longan trees. Longan fruit remain fresher if still attached to the branch, so efforts are made to prevent the fruit from detaching too early. Mechanical picking would damage the delicate skin of the fruit, so the preferred method is to harvest by hand. Knives and scissors are the most commonly used tools.

Fruit is picked early in the day to minimize water loss and to prevent high heat exposure, which would be damaging. The fruit is then placed into either plastic crates or bamboo baskets and taken to packaging houses, where the fruit undergo a series of checks for quality. The packaging houses are well-ventilated and shaded to prevent further decay. The process of checking and sorting are performed by workers instead of machinery. Any fruit that is split, under-ripe, or decaying is disposed of. The remaining healthy fruit is then prepped and shipped to markets.

Many companies add preservatives to canned longan. Regulations control the preserving process. The only known preservative added to canned longan is sulfur dioxide, to prevent discoloration. Fresh longan that is shipped worldwide is exposed to sulfur fumigation. Tests have shown that sulfur residues remain on the fruit skin, branches, and leaves for a few weeks. This violates many countries' limits on fumigation residue, and efforts have been made to reduce this amount.

Distribution
Longan is found commonly in most of Asia, primarily in mainland China, Taiwan, Vietnam and Thailand. China, the main longan-producing country in the world, produced about 1.9 e6MT of longan in 2015–2017. Vietnam and Thailand produced around 500 and 980 e3MT, respectively. Like Vietnam, Thailand's economy relies heavily on the cultivation and shipments of longan as well as lychee. This increase in the production of longan reflects recent interest in exotic fruits in other parts of the world. However, the majority of the demand comes from Asian communities in North America, Europe and Australia.

Advancements in enhanced longan growth
While longan yields average out to 2 to 5 metric tons per hectare, there have been observed yields of up to 19.5 mt/ha in Israel. When investigating the difference, researchers found that the biggest areas of improvement for lychee yield came in improving crop management practices and the ambience surrounding the fields.

Efforts have been made to prolong longan's relatively short shelf life with chemical treatments based on SO2 in 2014.

Advancements in selective breeding have allowed scientists to find a strain of longan containing a "high proportion of aborted seeds" at the end of a thirty year breeding program in 2001. Studies in 2015 that aimed to aid longan breeding efforts discovered that -20 degrees Celsius is the optimal temperature for long-term storage of longan pollen, a key ingredient in enabling longan breeding programs.

Diseases
Plant based diseases can affect both longan fruits and their trees, and the severity of these diseases can range from harmless cosmetic damage to rendering to the fruit inedible.

The most prevalent disease among longan plants is the Witch's broom, which can be found in all major longan-producing Asian territories, including China, Thailand, and Vietnam. Witch's Broom works on deforming longan skin, and at times having the plant prematurely drop their fruit, similar to the Phytophthora palmivora.

Another common disease that longan trees can carry is the aptly named Longan Decline, which is largely prevalent in Thailand, with reports finding that it could affect up to 40% of longan trees alone. Affected trees are more vulnerable to common tree pests and algae, and often bear low-quality fruit unworthy of yield.

Algal spot is another plant disease that can affect longan plants and trees. Common among tropical fruits, the disease mainly takes form as red-orange algae that can appear on a fruit-bearing tree's leaves or branches. Algal spot on longan plants, like many other tropical fruits, is caused by Cephaleuros virescens.

An oomycete disease that causes blight on leaves and foliage of a plant and affects the related lychee, Phytophthora palmivora, can also appear on both longan plants and fruit, particularly in the Thailand region. When affecting longan, it can create brown spots on the fruit in an erratic fashion, and can also cause longan to drop prematurely from the plant. Early symptoms can also include a dark necrosis on the plant itself.

Stem-end rot is a disease common amongst litchi and longan, and causes browning and rot on the stem of the fruit. Longan also suffer from various decay-accelerating fungi.

An oomycete disease that affects the related lychee - Phytophthora litchii - also afflicts D. longan.