What is Heart Rot

Information Provided by: COLLEGE OF TROPICAL AGRICULTURE AND HUMAN RESOURCE

University of Hawaii

Coconut Heart Rot: is a serious fungal disease that kill the single growing point of coconut palms by rotting the heart of the palms.

Background

Coconut plants have been relatively disease free in Hawaii. In contrast, serious lethal decline or lethal yellowing diseases of palms have killed thousands of trees in Florida and the Caribbean islands, cadang-cadang disease has killed millions of trees in the Philippines, and bud rot caused by Phytophthora palmiuora has caused large losses in many parts of the world. None of these devastating diseases has been found in Hawaii. Phytophthora palmiuora is common on hosts such as papaya and orchids in Hawaii, but its absence from coconut suggests that strains of P. palmiuora pathogenic to coco­nut are absent or very rare in Hawaii.

In the 1970s, a serious disease of coconut trees was found on Kauai. Infected trees usually died within a year. During the 1980s, the disease was also found on Oahu, Maui, and Hawaii. Interisland movement of nuts, seedlings, and large trees, plus tree-trimming operations, prob­ably contributed to the spread of this disease throughout the state.

Casual Organism

Diseased nuts and heart rots, followed by plant death, have been consistently associated with a Phytophthora species. Unlike P. palmi-vora, this new Phytophthora pathogen of coconut produces abundant and distinctive oospores, or sexual spores, in host tissue (Figs. 9A, 9B, 9C, and 9D). Each oospore is produced in a mother cell (oogonium) that has distinctive blisterlike swellings and a long base. In agar culture, oogonial protuberances become more frequent and consistent (Fig. 9E). Distinguishing between the new coconut Phytophthora and P. palmivora is therefore relatively easy.

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