Hawaii Coconut Protectors

Battling Coconut Heart Rot
on Oahu

Click to navigate through coconutprotectors.com:

Big Island...Maui...Oahu...Kauai...Related Diseases...Hawaii Landscape Magazine...Home

All photos can be clicked on to view larger images.

UH to renew search for coconut fungus cure

Kauai's ag station plans to pick up the hunt halted 8 years ago by lack of funds

January 1, 2001

By ANTHONY SOMMER

WAILUA, Kauai -- The search for a cure to a fatal fungus that has attacked about 20 percent of the state's coconut palm trees, probably Hawaii's best-known tourism icon, is about to be renewed by the University of Hawaii's agriculture experiment station on Kauai after an eight-year hiatus.

Experiments that began in the 1980s yielded a successful way to prevent the disease, but not a cure.

The project ended in 1992 when Hurricane Iniki wiped out all of the trees that were being studied. The state Legislature did not provide funding for more research until its 2000 session, when it appropriated $50,000.

The primary drum-beater for renewed funding was Philippe Visintainer, who owns the only business in Hawaii that provides preventive treatments, Hawaii Coconut Protectors, headquartered in Paia, Maui.

Visintainer also is head of the Maui Farm Bureau, and he said that's the hat he was wearing when he asked the state for money for new research on what he calls "the AIDS of coconut palms."

"What we really need is $200,000 a year, but that just wasn't a realistic request," he said.

The fungus is called Phytophthora katusae, but its common name is "coconut heart rot." It appears only in Hawaii, although similar fungi are found in other parts of the world.

Because large numbers of young coconut palms grow both in the wild and in plant nurseries, there is little concern the fungus ever will wipe out all of the trees in Hawaii. But it is a major concern for anyone who uses the trees for landscaping -- governments, businesses and homeowners. The cost of replacing a diseased tree can be considerable.

The fungus was first identified in 1971 and probably arrived in Hawaii about three years earlier, according to Jerry Ooka, the UH researcher who headed the earlier experiments on Kauai and who is planning, finally, to continue them. The university's research station is on Kauai's "Coconut Coast," an area heavily planted with coconut palms a century ago in anticipation of an industry that never materialized.

"The disease appears to go in cycles of four to five years." Ooka said. "It appears to spread most rapidly after heavy storms. A great number of trees on Kauai were affected following both Hurricane Iwa and Hurricane Iniki."

The fungus is most commonly found on the wet, windward side of the islands, but has begun showing up on leeward coasts recently. It is spread by the wind, on carriers such as birds and insects, and by gardening tools that have been in contact with diseased trees.

The first symptom is the death of the newest frond emerging from the top of the tree. But by the time that can be seen, the tree is doomed. During the course of the disease, a tree will lose all of its fronds.

UH's earlier research discovered that an annual dose of potassium phosphite injected with a pressurized syringe will boost a tree's immune system sufficiently to ward off the fungus.

Because it is a nutrient and not a fungicide, the material is treated by government agencies as a plant food and is not subject to regulation, Ooda said.

The chemical used by Visintainer varies only slightly -- to avoid patent infringement problems, Ooda said -- from that developed by the university. Visintainer claims a 90 percent success rate.

He charges $20 a tree or $15 if the customer has 50 or more trees. His customers are private owners, condominiums, hotels, resorts, and golf courses.

"We've tried to make it affordable because we want everyone to use it," he said. Hawaii Coconut Protectors opened for business in January 2000, and Visintainer said he has focused primarily on Maui. Since January 2001, he offered the service throughout the state.

Visintainer notes that it costs between $200 and $500 to have a diseased tree removed. Replacement trees cost $100 a foot, so a typical 50-foot tree sold by nurseries runs $5,000. Coconut palms grow a foot a year and reach a maximum height of about 100 feet.

A New Phytophthora Fruit and Heart Rot of Coconut

COLLEGE OF TROPICAL AGRICULTURE AND HUMAN RESOURCE

University of Hawaii

INTRODUCTION

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.

SYMPTOMS

Abnormal loss of small to nearly mature nuts has been a common early sign of this disease. Infected fruits have dark, mottled spots and rots. Irregular expansion of brown infected areas frequently creates circular green patches or islands of green tissue surrounded by diseased areas (Figs. 1A and B). Water soaking is also common on large immature fruits and appears as dark green, oily tissue bordering diseased areas. Very young diseased fruits less than 7.5 cm (3") long are generally brown without mottling. Internally, the infected husk of older fruits is reddish to red-brown (Fig. 2). The infected meat, or endosperm, is white, cream colored, or slightly brown. The pathogen may penetrate mature nuts by growing through the germination pore at the stem end of the nut.

The first symptoms on young or mature trees are wilting, discoloration, and death of the youngest leaf. Unfurled spear leaves may also die early in the course of this disease. Dead fronds are bent abnormally but remain attached to the trunk for a few weeks, drooping onto or between the older green leaves (Figs. 3 and 4). In the ensuing months, more leaves die and fall, leaving a few lower fronds (Figs. 5 and 6). Roots and lower trunk tissue remain healthy and functional for many months and continue to supply the lower leaves with nutrients and moisture. Eventually all of the fronds drop, producing leafless trunks.

Less frequently, older leaves die first, resulting in trees with only a few young, upright fronds. Because young leaves are vertically oriented, infected plants appear rigid or stiff.

By the time leaf death is observed, internal heart rot is already at an advanced stage. These diseased trees have large rotted areas that involve most of the terminal bud (Figs. 7A, 7B, 8A, and 8B). Killing of the single growing tip ultimately causes the death of the palm.

CAUSAL 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. This coconut Phytophthora is new to Hawaii and is unique in that it has not been found on any other host in the Islands. Pure cultures of the new Phytophthora were taken from diseased coconut collected on the islands of Kauai, Oahu, Maui, and Hawaii. These cultures were tested on healthy coconut fruits and young plants, and pathogenicity was confirmed on fruits (Figs. 1O, 11, 12, 13, and 14) and young plants.

The coconut Phytophthora resembles P. katsurae, a pathogen causing a serious disease on chestnut in Japan. Among all species of Phytophthora described by 1970, P. katsurae was the best match for identification of the coconut Phytophthora. The coconut pathogen was tentatively named P. katsurae. In Africa, a similar coconut disease reportedly has been caused by a pathogen assigned to P. heveae. Based on oogonial characteristics, this coconut pathogen from Africa appears similar to the coconut pathogen discovered in Hawaii and resembles P. katsurae more than P. heveae.

Fig. 1. Coconut fruits infected with Phytophthora. A, B. Diseased areas are mottled, brown, and black.

Irregular expansion of tha disease produces green islands surrounded by darkened diseased tissue.

Fig. 2. Diseased coconut fruit with darkened infected husk.

Fig. 3. Mature coconut tree with early external signs of heart rot. Note two young dead leaves.

Fig.4 young coconut plant with early signs of heart rot

Fig. 5. Young coconut plant in advanced Fig. 6. Stand of diseased coconut "trees

stages of heart rot 'with several dead leaves.

Fig 7. Coconut stem with severe heart rot associated with Phytophthira

A Longitudinal section. B close up

Fig. 8. Cross section of a coconut stem with heart rot. A. Section through heart and bases of surrounding petioles (leaf stems). B. Section through cylinder of petioles above the heart.

Fig. 9. Photomicrographs of Phyiophthora oospores in diseased coconut husks (A-D) and in pure agar culture (E). A. Spherical Phytophthora oospores. Magnification = 370x. B. Oogomum with long base and a single visible protuberance. C. Typical smooth oogonium with a long base common in host tissue. D. Smooth oogonia with short bases also found in the host. E. Typical oogonium with protuberances and long oogonial base formed in cultures. A thick-walled oospore is contained within the oogooium. Magnification of B to E = 925x.

Fig. 10. Early symptoms ofPhytoph-thora infection on coconut fruit.

Water soaking of the epidermal tissue and darkening of diseased areas,

three days after inoculation.

Fig. 11. Close-up of early symptoms on coconut fruit

after inoculation

Fig. 12. Typical irregular expansioa of Phytophthora lesion

on coconut fruit after inoculation

Fig. 13. Formation of islands of green tissue on inoculated fruit with calyx removed.

Fig. 14. White, crusty Phytophthora. spore masses on the stem end of the coconut fruit, two weeks after inoculation.

A recent reexamination of cultures of the coconut pathogen and P. kalswae by our laboratory indicates that the coconut pathogen may be significantly different from P. katsurae and is possibly a new species. Further comparative studies are in progress to identify the new pathogen.

AND CONTROL

Once trees are infected, death from the disease appears to be inevitable, and several hundred trees have been lost throughout the state since 1970. Because the host range of this Phytophthora appears to be confined to coconut, eradication and exclusion are feasible control options.

All infected trees and nuts should be destroyed by incineration or deep burial. Prompt removal of diseased trees will reduce the probability of soil contamination with the pathogen. Oospores of most Phytophthora species are able to survive in soil without the host plant. Removal of diseased material will also prevent spread of the fungus to healthy trees.

Many diseased trees have been observed in wet windward areas of Kauai, Hawaii, and Oahu. Growers should avoid collecting coconut planting material from these areas. Since mature trees may be infected yet remain symptomless for many months, careful selection of clean nuts and healthy seedlings and trees is necessary. Stock plants or young seedlings should be grown in relatively dry areas to minimize establishment of the pathogen on new plants.

Because the epidemiology of this disease in Hawaii is not known, the means by which it spreads is not specifically known. Based on studies of other Phytophthora diseases, wind-driven rain, insects, or other small animals are probably important factors in the spread of the disease. Moisture strongly favors the growth, spore production, and spread of Phytophthora and disease development by this fungus. Oospores of the fungus occur in very large numbers within diseased husks and trunks. These thick-walled resistant structures allow the fungus to survive for long periods in a dormant state. The fungus is probably seed-borne as oospores in the husk.

The removal of nut clusters and heavy leaf pruning of large trees have probably aided disease spread. Microscopic Phytophthora spores from diseased tissue will contaminate cutting tools and infect healthy trees during subsequent pruning operations. Furthermore, wounding the stem base by cutting off green fronds exposes highly susceptible plant tissue to Phytophthora infections. When feasible, tree trimming should be done during dry weather.

Tools should be cleaned, then immersed in a disinfestant after trimming operations on each tree are completed, especially at sites known to have this disease. Fungicides such as Subdue 2E (metalaxyl), Dithane M-45 (mancozeb), Aliette (fosethyl-Al), and Truban (ethazole) are known to be effective protectants against other Phytophthora diseases, but they are not effective for curing trees with advanced rots of the heart or terminal bud.

Limited control of this disease in the early stages may be attained by removing diseased fruits on trees that do not have young dead leaves, then protecting the wound surface with a pruning sealant, thus preventing disease progression into the trunk.

Please feel free to call, write or email for any further information.

Hawaii Coconut Protectors L.L.C.
P.O. Box 791314
Paia, HI 96779
Phone: 808-573-1850
Toll Free: 1-800-417-7435
Fax: 808-572-5036