Of the two economically important palms, oil and coconut, the coconut is the most susceptible to pests and diseases. Four major epidemic diseases have killed millions of coconut palms; in the absence of a visible pathogen these diseases are attributed to viruses. Animal pests and fungal diseases attack both types of palm.
The most important animal pest of palms is the rhinoceros beetle, occurring in the Far East, in Africa, in Central America and the Pacific Islands. It attacks and severely damages palms of all ages but is most important in young plantations. In the South Pacific Islands up to 50% of young palms have been destroyed. Several species of leaf-feeding caterpillars, principally on oil palms, can cause extensive defoliation.
Four major diseases (of uncertain origin) of coconut all kill affected trees. Bronze leaf wilt, which is found in Trinidad and the Guianas, kills the palm within 4-6 months of the onset of the disease. Lethal yellowing, which has been recognized in Jamaica and the Cayman Islands for over a hundred years, kills affected trees in 3 months. Palm seedlings replanted in the same area usually succumb to the disease after 2 or 3 years. Cadang-cadang kills palms in 5-6 years. It occurs in the Philippines where it has been present for at least 50 years, but its incidence has increased recently. It has been responsible for the death of 14 million coconut palms. Kerala wilt has killed 10 million coconut palms in Kerala State (India) alone. It kills the tree over a period of 3-15 years.
The diseases of oil palms are very dependent on cultural practices. When the palms are grown in small scattered units, the main disease is a trunk rot, which is caused by various species of ganoderma, but when they are grown in plantations fusarium wilt is liable to cause serious losses. The fungal disease, but rot, kills infected trees.