Title: Preventive treatment of lethal yellowing with oxytetracycline
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Title: Preventive treatment of lethal yellowing with oxytetracycline
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Creator: McCoy, Randolph E.
Publisher: Agricultural Research Center, IFAS, University of Florida
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PREVENTIVE TREATMENT OF LETHAL YELLOWING


WITH OXYTETRACYCLINE


by


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


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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

symptoms.

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

spread.

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
J

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.














Table 1.

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.


A
A


Treatment No. Healthy No. Diseased Percent Diseased

Group 1
Treated 24a 0 0
Control 4 16 80

Group 2
Treated 22 4 15.4
Control 2 23 92

Total
Treated 46 4 8
Control 6 39 86.7


a0ne treated palm killed by lightning

bFive control palms removed by owner, probably healthy.












Bibliography

Martyn, R. D. and J. T. Midcap. 1975. History, spread, and other palm

hosts of lethal yellowing. Univ. of Florida Agric. Expt. Station

Circular 405.

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

66:1148-1150.

Midcap, J. T. and R. D. Martyn. 1975. The Malayan Dwarf, a lethal yellowing

resistant coconut palm. Univ. of Florida Agric. Expt. Station Circular

404.













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Figure 1

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 =

Group 2.




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