PREVENTIVE TREATMENT OF LETHAL YELLOWING
R. E. McCoy & D. S. Williams
Research Report FL-77-2
UNIVERSITY OF FLORIDA AGRICULTURAL RESEARCH CENTER
Institute of Food and Agricultural Sciences 3205 S.W. 70th Avenue
Fort Lauderdale. Florida 33314
PREVENTIVE TREATfENT OF LETHAL YELLOWING WITH OXYTETRACYCLINE
Randolph E. McCoy and Donna S. Williams
University of Florida Agricultural Research Report FL-76-4
Agricultural Research Center, IFAS
Fort Lauderdale, Florida 33314 /
The lethal yellowing disease has devastated the tropical coconut palm
in Miami, Florida, and is now spreading rampant across Broward and into Palm
Beach Counties. Symptoms of lethal yellowing begin with premature nutfall and
browning of the new flower stalks. Yellowing usually begins in the bottom
fronds and spreadsup through the crown of the tree. Lethal yellowing is
always fatal, killing a tree about 4 months.after the initial appearance of
Lethal yellowing is believed to be caused by a mycoplasmalike organism.
Microorganisms belonging to this group are susceptible to tetracycline-type
antibiotics, and in fact, the antibiotic oxytetracycline hydrochloride has
been approved by the U. S. Environmental Protection Agency for use in con-
trolling lethal yellowing. Treatment methods are described in University
of Florida Circular S-228, available free from your County Agricultural Ex-
tension Office. This report details the results of a test performed in the
Fort Lauderdale area to determine the preventive value of oxytetracycline-HCl
when injected into healthy coconut palms located in areas of rapid disease
Materials and Methods: Fifty mature symptom-free "Jamaica Tall" coconut
palms in two separate active lethal yellowing foci in the Fort Lauderdale area
were selected for treatment with oxytetracycline-HCl soluble power, 22.5%
active ingredient (Diamond-Shamrock Corp.). Twenty-five trees in each area
were initially trunk injected with a hydraulic-type injector (Minute
Tree Injector Miami, Fla.) at the rate of 2 grams active ingredient
in 45 cc (1.5 oz.) aqueous solution per tree in October, 1975. Subsequent
treatments were made 4 and 8 months after the initial treatment at the rate
of 3 g active ingredient per tree. The hydraulic type injector was used in
the second and third rounds of treatments except where unfeasible because of
an occasional mechanical failure of the injector or upon encountering a tree
with a particularly hard or soft trunk. In these cases trunk injections were
made with the MaugetT Injector (J. J. Mauget Co., Burbank, CA), each tree
receiving 15 cc (0.5 oz.) concentrated solution containing the same antibiotic
dose used previously.
Twenty five trees in each area were selected as untreated controls. All
100 trees were monitored at monthly intervals for 14 months for disease inci-
dence and/or development of symptoms. Signs of remission of disease development
were cessation of further symptom development, fruit retention, and production
of healthy new creamy-white flower stalks.
Results and Discussion: The results of the preventive treatments after 14
months are given in Table 1. While only five of the 50 treated trees became
diseased, 39 of the 50 untreated trees developed disease symptoms during the
same period. The infection rate was higher in group 2; 92% of the control trees
succumbed to lethal yellowing and 15.4% of the treated trees developed symptoms
of disease. In group 1, 80% of the control trees were lost, while only 1 of the
treated trees became diseased, and complete remission of symptoms occurred within
2 months of retreatment of this tree. One apparently healthy tree in this
treatment group was killed by lightning.
SPercent disease incidence at monthly intervals for both groups is plotted
in Fig. 1.
The use of oxytetracycline-HCl on a preventive basis effected a significant
decrease in incidence of the lethal yellowing disease. Its therapeutic and pre-
ventive value has already been established (McCoy 1972, 1975, McCoy et al., 1976),
but is reconfirmed by this test. Although all 100 of the trees chosen for this
test were apparently healthy, nearly 90% of the control trees showed disease
symptoms during the 14 months duration of this test. A similar percentage of the
treated trees can be assumed to have been infected during the course of this
test; however, only 8% of these trees showed any disease symptoms after 14 months.
Of the four treated trees which did become diseased in this period, one showed
complete remission within 2 months of retreatment, one showed cessation of
symptom development and production of healthy new flower stalks, and two have
continued to develop new symptoms. These figures indicate that a tree receiving
preventive treatment was 12 times less likely to develop lethal yellowing than an
untreated tree over a one year period. While preventive treatment of healthy
coconut palms is not 100% effective, it can be used to maintain a majority of
the tall coconut palms presently in our landscape for an estimated 5 to 10 years.
It is highly recommended that the disease resistant "Malayan Dwarf" coconut be
planted now to ultimately replace the common "Jamaica Tall" variety of coconut
palm that is so highly susceptible to lethal yellowing.
Number of healthy and diseased coconut palms 14 months after be-
ginning a preventive treatment program on 50 apparently healthy trees
with oxytetracycline-HCl. Fifty untreated apparently healthy controls
were also selected at the start of treatment. These trees were in two
separate groups with 25 treated and 25 controls each.
Treatment No. Healthy No. Diseased Percent Diseased
Treated 24a 0 0
Control 4 16 80
Treated 22 4 15.4
Control 2 23 92
Treated 46 4 8
Control 6 39 86.7
a0ne treated palm killed by lightning
bFive control palms removed by owner, probably healthy.
Martyn, R. D. and J. T. Midcap. 1975. History, spread, and other palm
hosts of lethal yellowing. Univ. of Florida Agric. Expt. Station
McCoy, R. E. 1972. Remission of lethal yellowing in coconut palm treated
with tetracycline antibiotics. Plant Disease Reporter 56:1019-1021.
McCoy, R. E. 1974. How to treat your palm with antibiotic. Univ. of
Florida Agric. Expt. Station Circular S-228. 7p.
McCoy, R. E. 1975. Effect of oxytetracycline dose and stage of disease
development on remission of lethal yellowing in coconut palm. Plant
Disease Reporter. 59:717-720.
McCoy, R. E., V. J. Carroll, C. P. Poucher, and G. H. Gwin. 1976. Field
control of lethal yellowing with oxytetracycline-HCL. Phytopathology
Midcap, J. T. and R. D. Martyn. 1975. The Malayan Dwarf, a lethal yellowing
resistant coconut palm. Univ. of Florida Agric. Expt. Station Circular
0 0 0
2 4 6 8 10 12 14
Percent disease incidence in 50 treated and 50 untreated initially
symptom free coconut palms equally distributed in 2 geographically separate
active areas of lethal yellowing. Open circles = Group 1, closed circles =