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Copyright 2005, Board of Trustees, University
GULF COAST RESEARCH AND EDUCATION CENTER
IFAS, UNIVERSITY OF FLORIDA I 189
5007 60th Street East
Bradenton, FL 34203 Univ8Fiy fi forida
Bradenton GCREC Research Report BRA1989-9 JuT -1989
SUCCESSFUL MANAGEMENT OF SWEETPOTATO WHITEFLY IN
COMMERCIAL FLOWER PRODUCTION
James F. Price, David J. Schuster and James B. Kring~
Sweetpotato whitefly began to menace Florida's flower industries in 1986
(Hamon and Salguero 1987, Price et al. 1987). Heavy losses occurred
during that first year. The sweetpotato whitefly now is present
throughout most of the year and threatens ornamentals in all parts of
Florida.. This article provides the basic information necessary to
understand sweetpotato whitefly management and provides specific steps to
Only plants grown in tropical and subtropical regions were infested (Cock
1986) until sweetpotato whiteflies became established in greenhouse
ornamentals, where entire plants are moved among regions. When infested
plants arrive in temperate regions climatically unsuitable for the
sweetpotato whitefly, plants are often placed in greenhouses with suitable
climates. Movement of plant material within a newly infested region
further distributes the insect. The sweetpotato whitefly is found
throughout the tropical world and now is found in greenhouses in North
America, Europe and other temperate areas.
Sweetpotato whitefly is important to the ornamentals industry because of
the large number of crops it affects, the damage it causes to those crops,
and the human reaction to possible infestations. All living whitefly
stages and dead immature forms stay on leaves when the crop is sold.
Customers object to the appearance of plants with sweetpotato whiteflies.
Regulatory officials also object to the potential of insects infesting a
new location. The nymphal and adult stages of the whitefly produce
honeydews upon which sooty molds grow and also affect the appearance of
ornamental plants. In addition, whiteflies feeding on the foliage can
affect the color and growth of the plants.
1Associate Professor of Entomology, Professor of Entomology, and Adjunct
Important flower crops on which the sweetpotato whitefly causes serious
damage, include poinsettia, gerbera daisy and hibiscus. Greathead (1986)
listed 506 host plants and many are ornamentals.
Sweetpotato whiteflies are capable of transmitting certain viruses to
plants. Fortunately, at the present time no viruses important to
ornamental production are known to be transmitted. As the sweetpotato
whitefly and ornamental crops remain together, this may change.
Biology and Appearance
Adult sweetpotato whiteflies occur on the undersides of host leaves. They
feed on plant juices with their piercing and sucking mouth parts. The
adult whiteflies are white, narrow and less than 1/16 inch long. Females
lay about 6-12 eggs per day on poinsettia leaves during the daylight hours
(Janssen and Price, unpublished data). The eggs are laid singly or in
small groups on the undersides of leaves. They are cigar shaped, placed
on end, are creamy white when young, turn light brown in about a day and
hatch after one week. A first stage nymph, sometimes called a crawler,
emerges from the egg, moves less than 1/8 inch and attaches itself to the
lower surface of the leaf where the nymph remains for one week. The
scale-like nymph sucks plant juices. The nymph continues to develop on
the lower leaf surface into a non-feeding stage, sometimes called the
pupa. During this period the insect changes from the scale-like nymph
into an adult whitefly that usually emerges between mid morning and early
Various practices can prevent, delay or reduce the population. Following
is a list of practices to protect ornamental crops in Florida:
Purchase cuttings and liners known to be free of whiteflies.
Whitefly free stock will ensure that the crop is started free of the
insects from the onset. Reliable producers of propagative material
exist and should be used.
Plant crops in production facilities free of whiteflies. Adult
whiteflies can fly within the production facility from an older
infested crop to a younger crop free of the pest. To prevent such
contamination, new crops should be placed into production areas only
after a previous infested crop has been removed entirely and the
greenhouse fumigated. Removing the older hosts will remove all
immature whiteflies and many of the adults.
Remove weeds and other nonessential plants from the production area.
It is difficult to maintain adequate whitefly control on weeds and
other noncrop plants in and around the production facility. Since
whiteflies can move from these to crop plants, nonessential plants
should be eliminated.
Prohibit yellow clothing and equipment from being moved within the
production area. Whiteflies are attracted to yellow' clothing and
equipment. Do not use yellow in the production area except yellow
Scouting and Chemical Control
Scouting a crop regularly and using yellow sticky cards provide
information about the first arrival of whiteflies and the success of
management practices. Sticky cards should be placed among susceptible
plants from the time they arrive. Scouts should check cards once or twice
weekly for adults caught in the sticky material. Adults on traps placed
among newly arrived plants indicate the plants may have entered with
whiteflies. Inspect plants for insect stages present and apply the
insecticides appropriate to kill them (Table 1). Repeat applications in
Where yellow sticky traps continue to catch adults over an extended period
due to reintroduction or poor control, an insecticide to kill adults and
another insecticide (or the same one) to kill nymphs should be applied
weekly until control is realized. Since most pesticides do not kill
pupae, young adults may be observed daily for about one week after
Insecticide sprays must be applied to the undersides of leaves where all
stages of the sweetpotato whitefly live and they must contact the
insects. Whiteflies do not consume treated, leaf surface tissue and
immature whiteflies do not crawl long distances so they do not come in
contact with toxic particles. Therefore insecticides must be applied to
deposit toxic particles directly onto the insects. Good leaf coverage and
good insect control are difficult when plants are spaced closely and basal
leaves are close to the production surface. Whiteflies do suck plant
juices but few effective systemic insecticides are available for whitefly
Insecticides should be chosen for their effectiveness in controlling the
whitefly stages present (Table 1) and for management of insect resistance
to insecticides. The latter is achieved when choices of insecticides are
rotated among chemical classes each generation (Sanderson, 1988), which
would be about once a month for the sweetpotato whitefly.
During 1987 and 1988, about 60 insecticides were tested at the University
of Florida, IFAS, Gulf Coast Research and Education Center in Bradenton,
for their usefulness in sweetpotato whitefly management. Table 1 presents
insecticides broadly registered for use on "flower crops" in Florida and
found by the authors to be effective for the indicated stage. These
selections offer at least one product from each of five chemical classes
that can be used in field production and one from each that can be used in
greenhouse production. Other insecticides, not evaluated, also may be
In order for pesticides to be used legally, the pesticide label must
permit its use on the crop intended. Only pesticides with labels
permitting use in greenhouses are legal for that environment. Whenever a
pesticide new to one's production system first is used, the pesticide
should be tested on a small portion of the target crop and observed for
adverse crop effects.
The sweetpotato whitefly is expected to continue to be a problem for
Florida growers for years to come. However, informed producers will be
able to manage the whitefly and continue to produce high quality crops.
The authors wish to acknowledge the support of American Floral Endowment,
Florida Ornamental Growers Association, Gloeckner Foundation and Ecke
Poinsettias toward research reported herein.
Cock, M. J. W. 1986. Bemisia tabaci--A Literature Survey on the Cotton
Whitefly with an Annotated Bibliography. C.A.B. Internat. Inst.
Biol. Control. London. 121 pp.
Greathead, A. H. 1986. Host plants. Pages 17-26 in M. J. W. Cock, ed.
Bemisia tabaci--A Literature Survey on the Cotton Whitefly with an
Annotated Bibliography. C.A.B. Internat. Inst. Biol. Control.
London. 121 pp.
Hamon, Avas B. and Victor Salguero. 1987. Bemisia tabaci, sweetpotato
whitefly, in Florida .(Homoptera: Aleyrodidae: Aleyrodinae). Fla.
Dept. Agric. & Consumer Services Entomol. Circ. 292. 2 pp.
Price, James F., David J. Schuster and Don E. Short. 1987. Recent
advances in managing the sweetpotato whitefly on poinsettia. Fla.
Ornam. Growers Assoc. Newsletter 10(5):1-4.
Sanderson, John P. 1988. Whiteflies: Chemical control and insecticide
resistance. Pages 162-71 in A. D. Ali, ed. Proc. Fourth Conf. on
Insect and Disease Management on Ornamentals. Soc. Amer. Florists.
Alexandria, Va. 214 pp.
Table 1. Insecticides broadly registered for use on "flower crops" and
found by the authors to be effective for control of sweetpotato
Chemical Class and Product Site of Use
Found Effective against
Egg Nymph Pupa Adult
Potassium Salt of Fatty Acid:
1. Avid label makes no claim for
control of whiteflies.
2. Safer Insecticidal Soap may be toxic to adult whiteflies directly
contacted by wet sprays.