Coconut Palm Diseases
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Fruit Drop Caused by Leathal Yellowing
Fig. 1
Fruit drop caused by Lethal Yellowing.

Spear leaf and next youngest leaf exhibiting typical symptoms of Phytopthora bud rot
Fig. 9
Spear leaf and next youngest leaf exhibiting typical symptoms of Phytopthora bud rot.

ocos nucifera trunk collapsed upon itself due to Thielaviopsis trunk rot.
Fig. 18
C. nucifera trunk collapsed upon itself due to Thielaviopsis trunk rot.

Sabal palmetto (sabal palm) with wilted and dessicated leaves due to Ganoderma zonatum infection.
Fig. 26
Sabal palmetto (sabal palm) with wilted and dessicated leaves due to Ganoderma zonatum infection.

Basidiocarp (conk) of Ganoderma zonatum. Note glazed reddish-brown top surface and white undersurface. The "straight" side of the conk is directly attached to the trunk. There is no "stem" or "stalk" that attaches the conk to the trunk.
Fig. 27
Basidiocarp (conk) of Ganoderma zonatum. Note glazed reddish-brown top surface and white undersurface. The "straight" side of the conk is directly attached to the trunk. There is no "stem" or "stalk" that attaches the conk to the trunk.


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Leathal Yellowing
Caused by a tiny organism called a phytoplasma (Fig.1)

Lethal yellowing is the most important disease of coconut in Florida. Since LY was discovered in Key West more than 200 years ago, this disease has crept northward, killing hundreds of thousands of palm trees and endangering virtually all of the tall coconut palms in Florida. Lethal yellowing is caused by a tiny organism called a phytoplasma, which is visible only with the aid of an electron microscope. Early symptoms of LY are premature dropping of coconuts and blackening of flower stalks. The palm leaves then turn yellow, beginning with the lower leaves and progressing to the crown, which dies and eventually topples from the tree. The tree usually dies within six months after exhibiting the first symptoms of LY. 1

Foliar Yellowing SymptomsFoliar Yellowing Symptoms'Jamaica Tall' Cocos nucifera on left is exhibiting Lethal Yellowing symptoms of solitary, yellowed leaf ("flag leaf") in middle of canopy plus dead leaves hanging down around trunk.Foliar browning symptoms of Lethal Yellowing on Phoenix dactyliferaThe leaves of dwarf cultivars of Cocos nucifera affected by lethal yellowing usually do not turn yellow
Fig. 2 magnifying glassFig. 3  Fig. 4 magnifying glassFig. 5 magnifying glassFig. 6 magnifying glass
Leaf yellowing symptoms on Cocos nuciferaCocos nucifera spear leaf is dying just as the last leaves are discoloring
Fig. 7 magnifying glass Fig. 8 magnifying glass

Fig. 2,3.  Foliar Yellowing Symptoms

Fig. 4. 'Jamaica Tall' Cocos nucifera on left is exhibiting Lethal Yellowing symptoms of solitary, yellowed leaf ("flag leaf") in middle of canopy plus dead leaves hanging down around trunk.
Fig. 5. Foliar browning symptoms of Lethal Yellowing on Phoenix dactylifera
Fig. 6. The leaves of dwarf cultivars of C. nucifera affected by lethal yellowing usually do not turn yellow
Fig. 7. Leaf yellowing symptoms on C. nucifera
Fig. 8. C. nucifera spear leaf is dying just as the last leaves are discoloring

Further Reading
Lethal Yellowing of Palms from the University of Florida  pdf 7 pages
Palm Diseases Caused by Phytoplasmas: Lethal Yellowing and Texas Phoenix Palm Decline
from the University of Florida, Fort Lauderdale Research & Education Center



Phytopthora Bud Rot
Caused by Phytophthora palmivora (Fig.9)

Thielaviopsis paradoxa may cause this disease also.
The most common bud rot pathogen in Florida is P. palmivora. The first symptom is discoloration and wilting of the spear leaf and wilting/discoloration of the next youngest leaf. If severe, the spear leaf easily pulls from the bud.
In palms with a canopy above eye level, this first symptom is often missed. Instead, a lack of new leaves and an open-topped crown are often the first symptoms to be observed. Because the bud is dead, no new leaves emerge. Older leaves remain healthy for months after the bud dies.
In a nursery, water management and sanitation are critical for bud rot management.
Preventive fungicide applications are useful in a nursery situation for bud rot, but less so in a landscape with mature palms (palms with trunks).
Bud rot is also observed in association with cold damage. Cold damage allows entry of secondary pathogens, both fungi and bacteria. 2

Only the spear leaf and next youngest leaf are affected by the pathogen; older leaves remain healthyBud Rot of Cocos nuciferaMultiple Washingtonia robusta in this field nursery are being affected by Phytophthora bud rot. Those most affected were juvenile palms in a low-lying area.
Fig. 11 magnifying glassFig. 12 magnifying glassFig. 13 magnifying glass
The initial site of infection is on the unopened leaf blade of the spear leafThe spear leaf of this seedling palm has already died due to a bud rot pathogen. While the surrounding leaves appear healthy, the bud (apical meristem) of this palm has already rotted, and no new growth will occurThe spear leaf and next youngest leaves of this juvenile palm are exhibiting extensive necrosis due to a bud rot pathogenThe spear leaf and the next youngest leaves are desiccated and necrotic due to bud rot
Fig. 14 magnifying glassFig. 15 magnifying glassFig. 16 magnifying glassFig. 17 magnifying glass

Fig.11. Only the spear leaf and next youngest leaf are affected by the pathogen; older leaves remain healthy
Fig. 12. Bud rot of C. nucifera: no new leaves are emerging and crown is open-topped, while older leaves in canopy look healthy at this time.
Fig. 13. Multiple W. robusta in this field nursery are being affected by Phytophthora bud rot. Those most affected were juvenile palms in a low-lying area.
Fig. 14. The initial site of infection is on the unopened leaf blade of the spear leaf.
Fig. 15. The spear leaf of this seedling palm has already died due to a bud rot pathogen. While the surrounding leaves appear healthy, the bud (apical meristem) of this palm has already rotted, and no new growth will occur.
Fig. 16. The spear leaf and next youngest leaves of this juvenile palm are exhibiting extensive necrosis due to a bud rot pathogen.
Fig. 17. The spear leaf and the next youngest leaves are desiccated and necrotic due to bud rot

Further Reading
Bud Rot of Palm from the University of Florida pdf
Butt Rot of Palms from the Florida Department of Agriculture pdf



Thielaviopsis Trunk Rot
Caused by the fungus Thielaviopsis paradoxa (Fig.18)

Due to this disease, the palm trunk either collapses on itself or the canopy suddenly falls off the trunk, often without warning. The palm canopy may appear healthy prior to collapse.
Except for “stem bleeding,” which is common in C. nucifera (coconut), there may be no symptoms prior to collapse of the palm.
Only fresh trunk wounds will become infected by the fungus, so disease management includes limiting man-made wounds to the palm trunk, especially the upper third of the trunk.
If the disease is detected early, cutting out the rotted, infested wood followed by spraying the wound site with a fungicide may be useful.
There are no other methods to prevent or cure this disease. The palm should be removed immediately, and the diseased trunk portion destroyed but not recycled. 3

The canopy of this Phoenix canariensis fell off of the trunk due to Thielaviopsis trunk rot.Washingtonia robusta with trunk collapsed on itself due to Thielaviopsis trunk rotCross-section of Washingtonia robusta trunk illustrating that the rot caused by Thielaviopsis paradoxa occurs on only one side of the trunk and moves from the outside to the inside of the trunk.
Fig. 19 magnifying glassFig. 20 magnifying glass  Fig. 21 magnifying glass 
Cross-section of Cocos nucifera trunk illustrating that the rot caused by Thielaviopsis paradoxa occurs on only one side of the trunk and moves from the outside to the inside of the trunk."Stem bleeding" on a Cocos nucifera due to infection from Thielaviopsis paradoxaAn example of "stem bleeding" on a Cocos nucifera trunk. The top of the blackened area was very soft and could be easily pushed in with the fingersThe canopy of Cocos nucifera in the center is wilted and necrotic due to a trunk infection by Thielaviopsis paradoxa. The infection site was just below the oldest leaf base
Fig. 22 magnifying glassFig. 23 magnifying glass  Fig. 24 magnifying glass  Fig. 25 magnifying glass

Fig. 19. The canopy of this Phoenix canariensis fell off of the trunk due to Thielaviopsis paradoxa trunk rot.
Fig. 20. W. robusta with trunk collapsed on itself due to Thielaviopsis trunk rot.
Fig. 21. Cross-section of W. robusta trunk illustrating that the rot caused by Thielaviopsis paradoxa occurs on only one side of the trunk and moves from the outside to the inside of the trunk.
Fig. 22. Cross-section of C. nucifera trunk illustrating that the rot caused by Thielaviopsis paradoxa occurs on only one side of the trunk and moves from the outside to the inside of the trunk.
Fig. 23. "Stem bleeding" on a C. nucifera due to infection from Thielaviopsis paradoxa
Fig. 24. An example of "stem bleeding" on a C. nucifera trunk. The top of the blackened area was very soft and could be easily pushed in with the fingers.
Fig. 25. The canopy of C. nucifera in the center is wilted and necrotic due to a trunk infection by Thielaviopsis paradoxa. The infection site was just below the oldest leaf base.

Further Reading
Thielaviopsis Trunk Rot of Palm from the University of Florida pdf



Ganoderma Butt Rot

Caused by the pathogen Ganoderma zonatum (Fig. 26, 27)

This fungus degrades or rots the lower 4-5 feet of the trunk. All palms are considered hosts of this fungus. This fungus is not a primary pathogen of any other plant family.
Symptoms may include wilting (mild to severe) or a general decline. The disease is confirmed by observing the basidiocarp (conk) on the trunk. This is a hard, shelf-like structure that will be attached to the lower 4-5 feet of the palm trunk. However, not all diseased palms produce conks prior to death.
A palm cannot be diagnosed with Ganoderma butt rot until the basidiocarp (conk) forms on the trunk, or the internal rotting of the trunk is observed after the palm is cut down. The fungus is spread by spores, which are produced and released from the basidiocarp (conk).
Conditions that are conducive for disease development are unknown.
There are currently no cultural or chemical controls for preventing the disease or for curing the disease once the palm is infected.
A palm should be removed as soon as possible after the conks appear on the trunk. Remove as much of the stump and root system as possible when the palm is removed.
Because the fungus survives in the soil, planting another palm back in that same location is not recommended without special precautions. 4

Syagrus romanzoffiana (queen palm) dying from Ganoderma zonatum. Only the spear and one other leaf remain green.Three phases of basidiocarp (conk) development of Ganoderma zonatum. The white "button" near the top of the picture is the beginning stage of the conk. The lower-right structure is a mature conk. The lower-left structure is also a mature conk, but it is an old one; the underside of this conk is no longer white.A cross-section through a Cocothrinax sp. trunk with Ganoderma butt rot. The darkened area in the center is a symptom of the trunk rot.
Fig. 28 magnifying glass  Fig. 29 magnifying glass  Fig. 30 magnifying glass
Cross-sections of lower trunk of Syagrus romanzoffiana infested with Ganoderma zonatum. Top-left section is bottom section (section 1) and remaining sections progress up the trunk. Note darkening of wood due to fungal degradation (rot).Comparison of pygmy date palm sections that are either healthy (right) or diseased (left) with Ganoderma zonatum.ut palm stump with numerous basidiocarps (conks) of Ganoderma zonatum forming on it. The conks in the palm stump's center are crowding each other and thus are forming into shapes different from those on the outer edges of the stump.
Fig. 31 magnifying glassFig. 32 magnifying glassFig. 33 magnifying glass
Spore release from mature conks (same stump as Figure 33) has resulted in reddish-brown appearance of conks and surrounding area.
Fig. 34 magnifying glass

Fig. 28.
Syagrus romanzoffiana (queen palm) dying from Ganoderma zonatum. Only the spear and one other leaf remain green.
Fig. 29. Three phases of basidiocarp (conk) development of Ganoderma zonatum. The white "button" near the top of the picture is the beginning stage of the conk. The lower-right structure is a mature conk. The lower-left structure is also a mature conk, but it is an old one; the underside of this conk is no longer white.
Fig. 30. A cross-section through a Cocothrinax sp. trunk with Ganoderma zonatum butt rot. The darkened area in the center is a symptom of the trunk rot.
Fig. 31. Cross-sections of lower trunk of S. romanzoffiana infested with Ganoderma zonatum. Top-left section is bottom section and remaining sections progress up the trunk. Note darkening of wood due to fungal degradation (rot).
Fig. 32. Comparison of pygmy date palm sections that are either healthy (right) or diseased (left) with Ganoderma zonatum.
Fig. 33. Cut palm stump with numerous basidiocarps (conks) of Ganoderma zonatum forming on it. The conks in the palm stump's center are crowding each other and thus are forming into shapes different from those on the outer edges of the stump.
Fig. 34. Spore release from mature conks (same stump as Fig. 33) has resulted in reddish-brown appearance of conks and surrounding area.

Further Reading
Ganoderma Butt Rot of Palms from the University of Florida pdf



Further Reading
Key to Palm Problems from the Fort Lauderdale Research and Education Center ext. link

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Bibliography

1 Broschat, T.K. and Crane, Jonathan H. "The Coconut Palm In Florida." edis.ifas.ufl.edu. This document is HS40, one of a series of the Horticultural Sciences Department, Florida Cooperative Extension Service, Institute of Food and Agricultural Sciences, University of Florida. Original publication date April 1984. Revised June 2011. Web. 27 Apr. 2014.
2 Elliott, Monica L. "Bud Rot of Palm." edis.ifas.ufl.edu. This document is PP-220, one of a series of the Plant Pathology Department, Florida Cooperative Extension Service, Institute of Food and Agricultural Sciences, University of Florida. Original publication date Oct. 2005. Revised July 2012.Web. 25 Mar. 2014.
3 Elliott, M.L. "Thielaviopsis Trunk Rot of Palm." edis.ifas.ufl.edu. This document is PP-219, one of a series of the Plant Pathology Department, Florida Cooperative Extension Service, Institute of Food and Agricultural Sciences, University of Florida. Original publication date October 2005. Revised March 2012. Web. 30 Apr. 2014.
4 Elliott, M.L. and Broschat, Timothy K. "Ganoderma Butt Rot of Palms." edis.ifas.ufl.edu. This document is PP-54, one of a series of the Plant Pathology Department, Florida Cooperative Extension Service, Institute of Food and Agricultural Sciences, University of Florida. Original publication date November 2000. Revised June 2012. Web. 1 May 2014.

Photographs

Fig. 1,2,3,4,5,13 Harrison, N.A. Lethal Yellowing (L.Y) of Palm. N.d. University of Florida-IFAS. edis.ifas.ufl.edu. Web. 28 Apr. 2014.
Fig. 4 Broschat, T. K. "Lethal Yellowing (L.Y) of Palm. N.d. University of Florida-IFAS. edis.ifas.ufl.edu. Web. 23 Apr. 2014.
Fig. 5,6,7 Harrison, N.A. Lethal Yellowing. 2011. Screening Aid. In A Resource for Pests and Diseases of Cultivated Palms. Florida Department of Agriculture and Consumer Service, Division of Plant Industry and Identification Technology Program, CPHST, PPQ, APHIS, USDA; Fort Collins, CO. itp.lucidcentral.org/id/palms/resource/index.html. Web. 30 Apr. 2014.
Fig. 8 Elliott, M.L. Lethal Yellowing. 2011. Screening Aid. In A Resource for Pests and Diseases of Cultivated Palms. Florida Department of Agriculture and Consumer Service, Division of Plant Industry and Identification Technology Program, CPHST, PPQ, APHIS, USDA; Fort Collins, CO. itp.lucidcentral.org/id/palms/resource/index.html. Web. 30 Apr. 2014.
Fig. 9 Broschat, T. K. and Elliott, M. L. Bud Rot of Palms. N.d. University of Florida-IFAS. edis.ifas.ufl.edu. Web. 23 Apr. 2014.
Fig.11,12 Elliott, M. L. "Bud Rot of Palms. N.d. University of Florida-IFAS. edis.ifas.ufl.edu. Web. 23 Apr. 2014.
Fig. 14,15,16,17 Elliott, M.L. Bud Rot. 2010. Screening Aid. In A Resource for Pests and Diseases of Cultivated Palms. Florida Department of Agriculture and Consumer Service, Division of Plant Industry and Identification Technology Program, CPHST, PPQ, APHIS, USDA; Fort Collins, CO. itp.lucidcentral.org/id/palms/resource/index.html. Web. 30 Apr. 2014.
Fig. 19 Donselman, H. Thielaviopsis Trunk Rot of Palm. N.d. University of Florida-IFAS. edis.ifas.ufl.edu. Web. 30 Apr. 2014.
Fig. 20 Howard, F.S. Thielaviopsis Trunk Rot of Palm. N.d. University of Florida-IFAS. edis.ifas.ufl.edu. Web. 30 Apr. 2014.
Fig. 18,21,22,23 Elliott, M. L. Thielaviopsis Trunk Rot of Palm. N.d. University of Florida-IFAS. edis.ifas.ufl.edu. Web. 23 Apr. 2014.
Fig. 23,24,25 Elliott, M.L. Thielaviopsis Trunk Rot. 2010. Screening Aid. In A Resource for Pests and Diseases of Cultivated Palms. Florida Department of Agriculture and Consumer Service, Division of Plant Industry and Identification Technology Program, CPHST, PPQ, APHIS, USDA; Fort Collins, CO. itp.lucidcentral.org/id/palms/resource/index.html. Web. 30 Apr. 2014.
Fig. 26,27,28,29,30,31,32,33,34 Elliott, M. L. Ganoderma Butt Rot of Palms. N.d. University of Florida-IFAS. edis.ifas.ufl.edu. Web. 1 May 2014.

Published 1 May 2014 LR. Updated 6 Nov. 2015 LR
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