The publications in this collection do
not reflect current scientific knowledge
or recommendations. These texts
represent the historic publishing
record of the Institute for Food and
Agricultural Sciences and should be
used only to trace the historic work of
the Institute and its staff. Current IFAS
research may be found on the
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site maintained by the Florida
Cooperative Extension Service.
Copyright 2005, Board of Trustees, University
A HISTORY OF ORNAMENTALS RESEARCH
AT AREC HOMESTEAD
ROBERT B. MARLATT
UNIVERSITY OF FLORIDA
AGRICULTURAL RESEARCH AND EDUCATION CENTER
HOMESTEAD AREC RESEARCH REPORT SB78-1
Homestead AREC Research Report SB78-1 February 21, 1978
A History of Ornamentals Research at A*EC-Homestead
R. B. Marlatt1
i'rior to 1953 the only attention given to ornamental plants consisted of
collections for planting at the Center and a few diagnoses of diseased or infested
specimens. During 1953 Dr. R. A. Conover screened fungicides for control of
frangipani rust. By 1955 a suitable fungicide was selected and at the end of that
year accessions for the Center's collection exceeded 1,000. This work on plant
disease control marked the beginning of many outstanding contributions credited
to the Homestead researchers of ornamentals. Dr. Conover, in 1955, began search-
ing for poinsettias resistant to scab, another fungus disease. One hundred nine-
teen cultivars and seedlings of poinsettias did not reveal any plants capable of
It was not until 1957 that a scientist was hired to work exclusively with
ornamentals. Dr. L. A. McFadden was asked to "work on production problems of
O ornamental plants". He subsequently surveyed nurseries in Dade County and found
they were principally producing tropical foliage plants. Coping with diseases in
this subtropical rainy area was their most serious problem. He found bacteria
rotting dieffenbachias, a fungus was decimating philodendrons and other fungi were
causing heavy losses in peperomias and spathiphyllums. There were also serious
losses of cattleya orchids, sansevierias, scheffleras and palms. The most serious
diseases of cut flowers included botrytis rot and ray blight of chrysanthemums
and phyllosticta blight of snapdragons. Dr. McFadden's first research showed that
root-knot nematodes in pothos ground beds could be controlled with a fumigant.
The severe freeze of February, 1958, ruined many of the Center's experiments
because ornamentals were generally grown in unheated structures commonly used in
the subtropical climate. McFadden found a funglcidal control for poinsettia scab.
professor, University of Florida Agricultural Research and Education Center,
He also began in that year, however, a study of black splash disease of hibiscus,
* which remains a mystery even today. McFadden identified a bacterium that caused
severe stem rot of dieffenbachias, another problem that is still with us. During
the same year he began to emphasize research on bacterial diseases. This was a
natural choice, since he had been trained by one of the world's outstanding
scientists working with bacterial diseases.
In 1959 McFadden found a new bacterial disease of poinsettias. His research
with a bacterial disease of aglaonemas proved the culprit was the same bacterium
that rotted philodendrons. A fungus leaf spot of pothos was identified and
fungicide trials with chrysanthemums continued. Ultimately McFadden was coauthor
of a bulletin entitled "Chrysanthemum Diseases in Florida".
In 1960, an official project began at Homestead devoted entirely to diseases
of tropical foliage plants. this was particularly timely because the demand for
house plants was soon to rise steeply, outstripping the supply for many years.
The severe hurricane of 1951 damaged test plantings and destroyed about half
of the trees in the arboretum. McFadden's work continued with diseases of
poinsettias and chrysanthemums but more and more emphasis was being laced on
foliage plant diseases. Bacterial diseases of syngonium and aglaonema were also
being researched in 1962.
By 1963 fungous diseases of dieffenbachia, kalanchoe and philodendron were
no less a problem but fungicidal control was made possible through research
efforts. At that time Dr. D. 0. Wolfenbarger, working with effective insectides
and mi.icids, controlled scale insects on hibiscus and mites on roses.
Dr. J. E. Reynolds a plant pathologist, replaced McFadden in 1964 and
discovered a stem rot of neanthe bella palms. However, he left before the end of
the year. Dr. R. B. Marlatt was hired to fill the position in late 1964.
Without losing step, house plant disease research continued on fungous and
bacterial diseases of dieffenbachias and philodendrons. Dr. R. M. Baranowski
investigated the influence of an experimental miticide on chrysanthemums and roses.
Although mite control was accomplished, as so often happens with miticides, the
mites eventually became resistant to it, therefore further work on miticides was
By 1966 Marlatt became interested in several undescribed leaf diseases of
rubber plants. An experimental rubber plant grove was established for studies
and a leaf-infecting nematode was described as the cause of one leaf spot disease.
An extensive study of rose nutrition was also completed by Dr. C. W. Young.
Iropagation and culture of dieffenbachias were studied for optimum growth
by Marlatt in 1957. D. O. Wolfenbarger continued his efforts to control mites
on roses and also worked out the life cycle of a weevil on mahogany.
In 1953, a serious leaf spotting of commercially grown rubber plants existed
but harlatt could not attribute the problem to bacteria or fungi. He then began
a hydroponic nutritional study of the plant. He continued searching for the means
of migration of rubber plant leaf nematodes from soil to foliage. That same year
R. M. Baranowski tested 12 experimental riticides on six chrysanthemum varieties.
In 19S9 Marlatt finally found leaf nematodes reached rubber plant leaves by
getting into a premature grass seed stalk. When the stalk grew up to a rubber
plant leaf the worms crawled off the seed head and entered a leaf. That was the
first report of such a unique mode of infection. The control! mow the grass.
R. M. Baranowski continues his efforts to control mites on roses and scales on
orchids and was successful. Wolfenbarger also found a control for snails on
day-lilies. The hydroponic study by Marlatt revealed that the most serious leaf
spotting on rubber plant was due to potassium deficiency. The control was
successfully accomplished in a grove by Marlatt and Dr. G. Orth. The very
first proof that mangos become seriously infected by verticillium, a worldwide
fungus common to soils of Dade County, was offered by Marlatt. T. W. Young
* completed his extensive nutritional study of roses in this same year, 1970.
Another severe leaf spotting of rubber plant was found by Marlatt to be
S caused by a fungus. Another of his studies of rubber plant revealed the rate
of leaf production and general growth patterns of this tree. A search for
verticillium resistance in mango seedlings and cultivars was futile all through
In 1974 Marlatt showed that a white blotching of sansevieria leaves was due
to air temperatures of about 450 F. Decreasing nitrogen fertilizer application
decreased the chilling injury. He and Dr. W. H. ?:dings of Gainesville proved
that Natal plum, bottlebrush tree, oleander and Brazilian pepper can all be
infected by the same fungus, which caused destruction and death of many branches.
rhe growth of sansevieria was intensively examined by Marlatt in 1975 and
reported to the sansevieria producers.
In 1975 several leafspots of fiddle-leaf fig were observed, so a grove of
the trees was planted for Harlatt. He also began a hydroponic nutritional study
. for explaining the presence of areca palm leaf spots which had never yielded
fungi or bacteria.
Another big stride was made in 1976 toward helping the foliage industry.
Through the efforts of local growers, funds were raised for another large shade
house. The producers also convinced IFAS to create the position of Extension
Horticulturist, someone to advise foliage nurserymen. The position was filled
by Dr. R. L. Biamonte, who immediately began planning the new shadehouse and
surveying the needs of the now enormous tropical foliage industry in South Florida.
.hus, as house plant production increased vastly by numbers of nurseries
and expansion of established nurseries, AXEC-Homestead is also increasing its
capacity to serve the industry.