There is a single poisonous tree on the island of St. John USVI. ​

The tree is one of the deadliest plants known. It is protected by a small fence and may not be destroyed. The manchineel tree is protected by law. Although the last one on the island, the tree is prevalent throughout the Caribbean. There were two manchineel trees on St. John before the storms of Irma and Maria in 2017.

The tree is listed on the endangered species list. There are accounts of terrible illness and deaths throughout the Caribbean and Florida. The manchineel fruit is sometimes mistaken as an edible plum or apple, earning it the name beach apple. One account in BMJ [1] recounts an incident where the author ate some fruit from the tree. She pronounced the fruit as pleasantly sweet and plum-like. Hours later, however, it left her in excruciating pain and unable to swallow.

All parts of the tree are to be avoided. The sap can blister the skin and, if touched to the eye, can cause blindness.

Useful links

The fruit of the Manchineel tree. © Hans Hillewaert/CC BY-SA 3.0

https://commons.wikimedia.org/wiki/File:Hippomane_mancinella_(fruit).jpg

Strickland NH. Eating a manchineel "beach apple". BMJ. 2000;321(7258):428. doi:10.1136/bmj.321.7258.428 https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1127797/