Passage below taken from Longan, and will be edited.

An oomycete disease that affects the related lychee - Phytophthora litchii - also afflicts D. longan.^[1]

Trees bearing longan can carry a variety of diseases that affect longan growth and quality.

One of the most common diseases 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^[2]. Affected trees are more vulnerable to common tree pests and algae, and often bear low-quality fruit unworthy of yield^[2].

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.^[3]Algal spot on longan plants, like many other tropical fruits, is caused by Cephaleuros virescens^[4].

Phytophthora palmivora, a disease that causes blight on leaves and foliage of a plant, can 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.^[5]

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.^[6] Witch's Broom works on deforming longan skin, and at times having the plant prematurely drop their fruit, similar to the Phytophthora palmivora^[7].