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Y0 r Circular 405
History, Spread, and Other
Palm Hosts of
of Coconut Palms
R. D. Martyn and J. T. Midcap
Florida Cooperative Extension Service
Institute of Food and Agricultural Sciences
University of Florida, Gainesville
FIG. 5. LY symptoms in other palm species, a) healthy Christmas
p-n, b) LY infected Christmas palm, c) LY infected borassus palm.
FIG. 2. Symptoms of LY in coconut palms: a) shelling, b) healthy
inflorescence, c) blacken inflorescence from a LY infected palm,
d) yellowing of fronds.
History, Spread, and Other
Palm Hosts of Lethal Yellowing
of Coconut Palms
R. D. Martyn and J. T. Midcap'
History and Spread
The coconut palm (Cocos nucifera), although
not native to the United States, gives subtropical
Florida its beauty and charm more than any other
plant. In the time the palm has been in the state,
it has managed to survive many hazards, includ-
ing hurricanes and urban development. How-
ever, the coconut palm's very existence now is
threatened by a relatively new hazard that has
proved to be even more devastating. This hazard
is the disease lethal yellowing (LY) of coconut
Symptoms of LY resemble symptoms of certain
other palm diseases. For many years attempts
to identify the causal agent of LY focused on
fungi, bacteria, nematodes, viruses and nutri-
tional deficiencies. In 1972, evidence began to ac-
cumulate that has been added to in subsequent
years, so that in 1975 strong circumstantial evi-
dence suggests that the causal agent is a my-
coplasmalike organism that resembles a bacterium
without a rigid cell wall. The mode of spread of
this organism is still not known, but it is thought
to move from diseased to healthy palms by an
insect. Research is currently underway to ident-
ify the carrier (s) involved.
Lethal yellowing attacks the 'Jamaican Tall'
as well as several other varieties of the coconut
palm and was first reported in Jamaica near Mon-
tego Bay in 1891. By 1944, the disease was
epidemic and was killing the coconut palm popula-
tion along the coast at the rate of 200,000 trees
Lethal yellowing remained a Carribean disease
until 1955 when it was reported in Key West,
Florida. Although this is the first official report
of the disease in the United States, it may well
have been in Key West since 1936, when 21 trees
SResearch Associate in Plant Pathology, Extension Ornamental
died mysteriously of a "yellowing" condition
similar to LY. But after two years the disease
was not observed again until 1955.
It now appears that LY is present throughout
the Carribean, including the following countries:
the Dominican Republic, Cuba, Haiti and the Ba-
hamas. It has also been reported in three countries
in West Africa.
During the 13 year span from 1955-1968 when
LY was epidemic in Key West, 75 percent of that
island's coconut palm population-or about 15,000
individual palms-were killed. By 1968, no new
cases of LY had been reported in Key West and
the disease appeared to have run its course. How-
ever, in 1970 LY was observed on Key Largo, al-
most 100 miles up the island chain. In 1971 the
disease moved to Little Torch Key, and by Sep-
tember, 1971 it reached Coral Gables on the
Surveys conducted by the Division of Plant In-
dustry of the Florida Department of Agriculture
and Consumer Services began immediately and
showed 57 infected palms within a 100 square
block area of Coral Gables. Within the next 12
AL EA West Palm Beach
S PAL BERNH
Hple I CTNIER I RO
Naples COLLIE OWARD Ft. Lauderdale
COCONUT QUARANTINE S Miami
in SOUTH FLORIOA n n Cral ales
FIG. 1. Counties in Florida where lethal yellowing has been re-
months, the disease spread south to Key Biscayne,
east to Miami Beach and north to Carol City,
claiming over 1200 coconut palms. The disease
continued to move up the east coast of Florida.
In February, 1972 it was reported in Broward
County and a year later in Palm Beach County.
By August, 1974 LY was observed in Martin
County and by October, 1974 it had spread west
into Collier County.
At present, the six counties where the disease
has been reported are under strict quarantine in
order to prevent uncontrolled movement of sus-
pected host palms out of these areas.
It is estimated that LY has already killed a
third of Florida's coconut palms (200,000 trees),
70,000 Christmas palms and an undetermined
number of other palm species. And the disease is
continuing to spread.
Symptoms in Coconut Palms
To the untrained eye, lethal yellowing may
easily be confused with other yellowing and de-
foliating maladies of coconut palms, including
such diseases as fungal bud rot, nutrient defi-
ciencies, insects, nematode and lightning damage.
Observations over the years, however, have led to
the recognition of four symptom stages for LY
in coconut palms, of which at least one is defin-
itive for the disease.
The first symptom of LY is the premature drop-
ping of most or all of the coconuts regardless of
size (Fig. 2a). This is termed "shelling" and
most of the fallen nuts will have a brown or black
area immediately under the calyx on the stem end.
The second stage, which is definitive for LY,
is the blackening of new inflorescence tips (flower
stalks). This may be observed as they break
through the spathe (the structure which enclosed
the inflorescence) and is quite distinctive because
the inflorescence of healthy trees are a golden-
yellow color (Fig. 2b & 2c). In addition to the
blackened tips, almost all of the male flowers will
be dead and no fruit will be set on such a flower
The third symptom stage is the one from which
the disease gets its name. The fronds turn yel-
low, usually beginning with the older ones near
the bottom and advancing upwards toward the
crown (Fig. 2d). In many cases, one specific
frond will turn yellow first giving a character-
istic "flag" appearance. Fronds that have yel-
lowed will die, turn brown and hang down, but
tend to cling to the tree instead of falling off.
The fourth and final symptom occurs only after
all the leaves have been killed, including the newly
emerged spear leaf. Death of the bud occurs,
followed by the falling away of the top of the
tree, leaving a bare trunk or "telephone pole"
(cover photo). Infected trees usually die within
3-6 months after the appearance of the first symp-
As yet, nothing can be done to cure a coconut
palm once it has been infected with the LY organ-
ism. However, several things can be done to slow
the rate of disease spread. Since an infected
palm may show symptoms for 3-6 months before
it dies, and thereby serve as a source of inoculum
for healthy palms, any palm showing LY symp-
toms should be removed and destroyed.
Research at the University of Florida Agri-
cultural Research Center in Ft. Lauderdale led to
the discovery that injection of the antibiotic
oxytetracyclinee" into the trunk of diseased coco-
nut palms resulted in remission or stoppage of
LY symptoms. This treatment can extend the
life of diseased palms if the treatment is applied
before fronds begin to yellow. It must be noted,
however, that this antibiotic treatment does not
cure the tree and the treatment must be repeated
every four months or symptoms will again appear
and culminate in death of the palm. (See Circu-
lar S-228, "How to treat your palm with anti-
Possibly the best bet for the control of LY lies
in the planting of the "Malayan Dwarf" varieties
of the coconut palm which are, as far as is
known, resistant or immune to lethal yellowing.
(Fig. 3). Thousands of seed nuts have been im-
ported and planted in Key West and Stock Island
and have remained disease free.
Logically, then and until research develops
other alternatives, the best combination to com-
bat lethal yellowing is to remove any diseased
tree and replace or start new plantings of the
resistant "Malayan Dwarf" variety.
Other Palm Hosts of Lethal Yellowing
Until recently, lethal yellowing was believe
to affect coconut palms only; however, research
since 1971 has shown this to be incorrect. At tl
present time, 15 different species of palms ai
suspected of being susceptible to LY, including
such popular species as the Christmas Pall
(Veitchia merrillii) and the Canary Island Dal
Palm (Phoenix canariensis). All 15 species, *'
eluding the coconut palm, are under strict quarai
tine by the Division of Plant Industry within the
six county area.
The quarantine list is based on the appearance
of symptoms in diseased palms that are identical
or similar to those of lethal yellowing of coconut
palms. In addition, the detection of the suspected
causal agent (mycoplasma-like organism) in the
vascular tissues of palms thought to be infected
with LY is also strong evidence, since these
organisms have not been found in healthy palms.
The current list of suspected hosts of lethal yel-
lowing includes the following species; however,
as new information is generated the list may ex-
pand to include additional species:
Cocos nucifera-coconut palm
Veitchia merrillii-adonidia or Christmas palm
Pritchardia pacifica-Fiji Island fan palm
Pritchardia thustonii-Thurston palm
Phoenix canareinsis-Canary Island date palm
Phoenix dactylifera-date palm
Phoenix reclinata-Senegal palm
Arikuryroba schizophylla-arikury palm
Caryota mitis-cluster fish-tail palm
Borassus flabellifer-palmyra palm
Mascarena verschaffeltii-spindle palm
Corypha elata-talipot palm
Trachycarpus fortunei-windmill palm
Chrysalidocarpus cabadae-cabada palm
Dictyosperma album-hurricane or princess
The widespread plantings of these palms, es-
pecially the Christmas and date palms, increase
the hazard of LY to many palms now growing in
Recognition of LY symptoms in palms other
than the coconut palm is difficult, because almost
all of these species have not been observed ad-
equately enough during early stages of infection
to catalog symptom development precisely. The
first two symptom stages of LY in these suscep-
tible palms, are the same as for the coconut palm
-that is, the premature dropping of fruit (shell-
ing) and the blackening or necrosis of the new
The third symptom, which is in many cases the
first obvious sign of trouble, is the discoloration
of the fronds. It is at this stage of infection
where the symptoms differ for individual species.
FIG. 3. Mature "Malayan Dwarf" coconut plam.
In general, frond discoloration due to LY falls
into two distinct categories: those in which the
fronds turn a golden-yellow before dying and
those in which the fronds turn a greyish-brown.
/ Palms in the first symptom category, yellowing of
fronds, are coconut palms, talipot palms (Fig. 4),
both species of pritchardia, arikury, windmill,
princess and spindle palms.
The progression of symptoms is similar to that
in coconut palms where the lower fronds turn a
golden-yellow, but often one specific frond will
turn before any others giving a "flagging" ap-
pearance. The fronds remain yellow for various
lengths of time before turning brown and dying.
The fronds have a tendency to break at the leaf
base junction and hang down somewhat like a
collapsed umbrella. Fronds may cling to the tree
instead of falling to the ground.
The yellowing usually advances from the older
to the younger fronds with the spear leaf the last
to turn. Once the spear leaf shows symptoms,
death of the crown occurs followed by a falling
away of the top of the tree leaving a topless bare
The remaining susceptible palms on the list fall
into the second symptom category, browning of
fronds, or fronds that develop a "dried out look."
The Christmas palm or adonidia is perhaps the
best example of this group (Fig. 5a). The first
two symptom stages in these palms are also sim-
FIG. 4. LY infected talipot palm (Corypha elata) showing yellow
ilar to symptom development in LY-infected coco-
nut palms. Frond discoloration is not as dramatic
nor is it as easily detected in early stages of de-
velopment as in coconut or pritchardia palms.
First evidence of infection is a brownish "water
mark" along the margin of the pinnae or leaflets.
Browning gradually extends to the entire frond
giving it a dried out appearance. As in other LY
infected palms, the older leaves tend to break
easily at the junction of the leaf-base and the mid-
rib, whereas younger fronds tend to break within
the lower region of the pinnae. Unopened in-
florescences may have a distorted or twisted ap-
pearance. Death of the bud follows and falls
away resulting in a bare topless trunk (Fig. 5 b).
In addition to the Christmas palm, the boras-
sus (Fig. 5c), cabada, cluster fish-tail and the
three species of Phoenix palms all show similar
In summary, the suspected causal agent of
lethal yellowing of coconut palms has been found
in 14 other palm species, including such popular
ornamentals as the Christmas palm and date
palms. Each of these infected species exhibit a
premature dropping of fruit and a necrosis of the
newly emerged inflorescence while frond dis-
coloration may be of two basic types-yellowing
Because there is no cure for lethal yellowing at
the present time, any palm showing LY symptoms
should be removed and destroyed. Replace dis-
eased palms with the resistant 'Malayan Dwarf'
coconut palm or other non-susceptible palms.
Contact your county Extension office for informa-
tion on suitable replacement palms.
The authors wish to thank and acknowledge
the following persons for giving generously of
their time and information during numerous dis-
cussions concerning lethal yellowing: J. W. Miller
and C. H. Gwin (Division of Plant Industry);
D. H. Romney (Coconut Industry Board, Ja-
maica); and D. L. Thomas, R. E. McCoy, J. A.
Reinert, D. A. Roberts, and L. H. Purdy (Uni-
versity of Florida).
COOPERATIVE EXTENSION WORK IN AGRICULTURE AND HOME ECONOMICS
(Acts of May 8 and June 30, 1914)
Cooperative Extension Servce, IFAS, University of Florida
'ngle copies free to residents of Florida. Bulk rates
available upon request. Please submit details on
request to Chairman, Editorial Department, Institute
of Food and Agricultural Sciences, University of
Florida, Gainesville, Florida 32611.
This public document was promulgated at an
annual cost of $2694.60, or 6.74 cents per
copy to assemble the best information known
about lethal yellowing of palms to inform
Floridians about this disease.