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record of the Institute for Food and
Agricultural Sciences and should be
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Copyright 2005, Board of Trustees, University
OCT 23 1987
GULF COAST RESEARCH AND EDUCATION ENTER
IFAS, UNIVERSITY OF FLORIDA University of Florida
5007 60TH Street East
Bradenton, FL 34203
Bradenton GCREC Research Report BRA1987-21 September 1987
RECENT ADVANCES IN MANAGING THE SWEETPOTATO WHITEFLY
James F. Price, David J. Schuster and Don E. Short1
Poinsettia growers in Florida, unlike elsewhere in the U.S., largely have
been spared problems with the common greenhouse whitefly (Trialeurodes
vaporariorum (westwood)). However, a more difficult to manage pest, the
sweetpotato whitefly (Bemisia tabaci (Gennadius)) now has appeared on
poinsettias in California, Florida, Georgia and North Carolina. Since
this whitefly is easily moved on infested cuttings and finished plants and
is known to occur in areas producing these products, it likely will be
found soon in other states. In 1986, this insect emerged as the most
important pest of Florida's $8 to $10 million poinsettia crop (Ball 1987)
and since then has spread to other greenhouse crops, including gerbera
daisy and hibiscus.
To a non-specialist, the sweetpotato whitefly looks much like the common
greenhouse whitefly, however adults of the former hold their wings more
tightly against their bodies and appear smaller. Adults of both species
have white, unmarked wings and appear as dandruff-like flecks on the
undersides of leaves. In areas where the sweetpotato whitefly is
suspected, host crops should be scouted for the insect at least once a
week. Scouts should look for adults resting on the undersides of upper
leaves or flying from those leaves when disturbed.
Scouts at the IFAS Gulf Coast Research and Education Center in Bradenton
monitor whitefly adults using 3" X 12" X 1/4" lemon yellow Plexiglass
strips covered with a very thin film of cooking oil (Butler, et al.
1986). These yellow traps are placed horizontally on greenhouse and field
production surfaces for about 3 hours on bright mornings. Whitefly adults
are attracted to the yellow strips and become stuck in the cooking oil.
When the traps are collected, scouts eliminate whiteflies that are not the
1Associate Professor and Professor of Entomology (GCREC) and Professor of
Entomology, Department of Entomology and Nematology, University of
Florida, Gainesville, FL.
size, shape or color of known sweetpotato whiteflies also stuck in an oil
film and count those that are "suspected sweetpotato whiteflies"
(whiteflies can not be identified conclusively in the adult form). When
suspected sweetpotato whiteflies are caught, foliage of known host plants
nearby is carefully inspected for immature forms that can be identified
conclusively (Hamon and Salguero 1987).
This system has been very effective to detect sweetpotato whitefly
infestations efficiently, early in their development and to indicate
effects of pesticidal and other control measures. Population monitoring
by this method can be performed by scouts trained to recognize the
suspected sweetpotato whitefly impinged on oil but, may not be reliable
when used by less trained individuals.
Leaves found with suspected sweetpotato whitefly colonies and the skins
cast by newly emerged adults, should be given to local Cooperative
Extension Service personnel to obtain reliable identifications.
Damage and Distribution
Sweetpotato whiteflies damage greenhouse crops by sucking their juices, by
making the plant unattractive or unacceptable due to the presence of the
whiteflies or their cast skins and by secreting honeydews upon which sooty
molds grow. In addition, sweetpotato whiteflies can vector viruses that
recently have been responsible for tremendous yield losses in southern
California vegetable crops (Duffus and Flock, 1982). The sweetpotato
whitefly is not known to be spreading viruses detrimental to poinsettias.
This whitefly has been recognized for some time as a serious pest of
cotton and other field crops in southern California and Arizona, Central
America, West Indies, South America, Africa and Asia. It was first noted
in Florida in 1894 and later in Washington, D.C., Arizona, California,
Texas, Georgia and Maryland (Russell 1975). Now that this insect has
become a pest in the greenhouse, its range may extend into the more
This insect is known to attack 506 plant species in 74 families, many of
which are normally grown in close proximity to poinsettia crops. The
greatest number of hosts are in the families Fabaceae, Asteraceae,
Malvaceae, Solanaceae, Euphorbiaceae, Convolvulaceae and Cucurbitaceae
The development of the sweetpotato whitefly into an important greenhouse
pest is unexpected. Lopez-Avila (1986) summarized the present
understanding of the economic damage by the sweetpotato whitefly and cited
only one former occurrence of this pest in a greenhouse crop, vegetables
Since past problems largely had been limited to field situations, little
information has been developed about this pest in the greenhouse
environment until now. Although research under greenhouse conditions at
the University of Florida IFAS research centers in Bradenton and Apopka
was only recently initiated, much information already has been gathered.
Certain additional biological information can be compiled from field
crops, such as cotton; however, the duration of this insect's life stages,
the numbers of eggs laid and other biological processes are closely
related to the host plant species and their environments (Coudriet et al.
On poinsettias grown in a CGREC greenhouse, where summertime temperatures
ranged from about 80 to 95 F, the development process from egg laying to
adult emergence required an average of about 23 days, although some adults
emerged in 18 days. Eggs laid on the undersides of poinsettia leaves
usually were spaced unevenly and arranged in small groups. Females laid
an average of 81 eggs in 8 days of adult life at 80 F on cotton (Butler
and Henneberry 1985). Eggs hatched in less than a week and produced tiny
crawlers that stayed near the empty egg shell. After about 1 day, the
nymph attaches to the leaf where it stays for the remain 12 or more days
of immature life. During the earlier portion of this sessile period the
nymphal whiteflies suck plant juices and secrete sugary honeydews; the
latter portion of the sessile period is a nonfeeding, resting period.
Cultural Management Considerations
Management of the sweetpotato whitefly on poinsettia is difficult
particularly because of this insect's resistance to important insecticides
long used for its control on cotton in southern California, Arizona and
other parts of the world (Prabhaker et al. 1985) and because of its
protected habitat on the lower surfaces of leaves. The best management,
however, begins with sound sanitation and other cultural practices.
For example, poinsettias should not follow a crop on which the sweetpotato
whitefly had been present, until one week or longer of warm production
temperatures has past without a host. This warm, host-free period is
necessary to starve adults left behind the crop. Since many weeds are
hosts, all weeds should be removed from within and around the poinsettia
production area. Infested weeds and crop plants should be buried, burned
or bagged and hauled to a dump.
Since the sweetpotato whitefly can enter a production greenhouse on
cuttings, it would be wise to purchase these from a producer free of the
whitefly rather than to produce cuttings from mother stock on a local
infested farm. Since whiteflies are especially attracted by yellow (Mound
1962) and may be moved into production facilities on clothing, workers in
infested areas should avoid yellow garments.
Growers should restrict the distribution of this whitefly and maintain
their reputations for production of quality crops by not shipping infested
poinsettias. This practice not only will prevent losses to other growers
but also will help to maintain markets for the shipper and others in that
Pesticidal Management Considerations
3. F. Price -and D. J. Schuster (GCREC Bradenton) have identified
compounds, permitted for use on poinsettia, that provide a useful level of
control of either adult or nymphal sweetpotato whiteflies. Thus, IFAS
personnel now recommend that, for poinsettias under more than minimal
pressure from the sweetpotato whitefly, pesticides should be applied twice
weekly for adult control and twice weekly for nymphal control through the
period of one whitefly generation (about three weeks). Subsequently,
weekly applications of pesticides detrimental to adults and nymphs may be
sufficient to maintain control. Table 1 lists those compounds, permitted
for use on poinsettias, that provide a useful level of control for adult
and/or nymphal sweetpotato whiteflies. Other registered and effective
compounds may exist that have not yet been evaluated.
Table 1. Recently evaluated insecticides, permitted for use on poin-
settia in Florida, found effective for against sweetpotato
whitefly and not found to be phytotoxic on V-14 Glory prebract
Permitted for Greenhouse Grown Poinsettias:
Adult Target Stage Nymphal Target Stage
Sulfotepp (Plantfume 103 smoke) Permethrin (Pramex 2EC)
Permethrin (Pramex 2EC) Bifenthrin (Talstar 10WP)
Abamectin (Avid 0.15EC) Abamectin (Avid 0.15EC)
Endosulfan (Thiodan 50W) Aldicarb (Temik 10G)
Lindane (Lindane No. 200 Spray)
Bifenthrin (Talstar 10WP)
Permitted on Field Grown Poinsettias:
Adult Target Stage Nymphal Target Stage (*)
Permethrin (Pramex 2EC) Permethrin (Pramex 2EC)
Abamectin (Avid 0.15EC) Abamectin (Avid 0.15EC)
Endosulfan (Thiodan 50W) Fluvalinate (Mavrik 2E)
Aldicarb (Temik 10G)
Several compounds were identified as being effective for control of adult
and/or nymphal sweetpotato whiteflies, but are not useful for poinsettias
due to phytotoxicity problems and/or lack of proper poinsettia labelling.
Products found to be effective for control of nymphs and adults, but which
can not be used on poinsettias include: Ambush 2E + Butacide, Pyrenone
EC, Danitol 2.4EC, Zolone 3EC, and Asana 1.9EC. Two additional products
were effective for nymphs only: Margosan-O and Apex 5E. These compounds
are candidates for future use in poinsettia production after elimination
of phytotoxic properties where such exist and after proper registration.
Recent experiences among Florida growers have shown that one pesticide may
perform well on one farm but not on another. This occurs because the
genetic characteristics among local whitefly populations may diverge and
because differing production practices may lend themselves to greater or
poorer success with a certain pesticide. A grower may need to change
certain production practices or otherwise abandon the use of a pesticide
others have found suitable.
Growers should rotate pesticides used, as much as is practical, among
different classes of compounds to extend the useful life of effective
insecticides. This is particularly important in the case of the
sweetpotato whitefly since resistance in this insect to certain synthetic
pyrethroids and organophosphorous pesticides is already known in southern
California (Prabhacker et. al 1985). Classes of the listed pesticides are
chlorinated hydrocarbon: endosulfan and lindane
synthetic pyrethroid: permethrin, fluvalinate, bifenthrin
bacterial fermentation product: abamectin
Poinsettias have been grown in Florida largely without pests for which
thorough pesticidal coverage of the abaxial leaf surfaces was critical.
This has permitted a cropping system of closely spaced plants with dense
foliage growing close to the ground--a situation making thorough
pesticidal coverage very difficult. Since the sweetpotato whitefly spends
most of its life on undersides of leaves, growers clearly must amend their
management practices to permit increased pesticidal coverage there.
Plants must be spaced to permit effective use of the proper pesticide
Pesticide labels inform users how to apply pesticides effectively, safely
and legally. Always follow the label and apply pesticides to poinsettias
only when permitted and in the production environments permitted. Never
use a pesticide or method of application not thoroughly tested for the
intended production system--serious losses from plant damage could occur.
Sound judgement requires that a small portion of each crop variety and
growth stage be treated and observed for a few days before treating the
larger production area. Since poinsettias are most vulnerable to
pesticide damage after bracts begin to show color, whiteflies should be
well-controlled by that point in the crop cycle.
IFAS researchers are continuing to identify compounds effective for
sweetpotato whitefly management with an emphasis on products that already
are permitted for use on poinsettias or are likely to be permitted for
that use soon. Additional promising compounds are being evaluated in
order to identify those for which future registrations should be sought.
Since this research program is an ongoing pursuit, IFAS recommendations
will change as new information develops.
(The use of trade names in this report does not constitute endorsement by
the University of Florida of one product to the exclusion of other
properly labelled products.)
1. Ball, Vic. 1987. Viewpoint. Grower Talks. 50 (11): 12,14.
2. Butler, G. D., Jr. and T. J. Henneberry. 1985. Bemisia tabaci
(Gennadius), a pest of cotton in the Southwestern United States.
USDA ARS Tech. Bull. 1707. 19pp.
3. Butler, G. D. Jr., T. J. Henneberry and W. D. Hutchison. 1986.
Biology, sampling and population dynamics of Bemisia tabaci. Agric.
Zool. Rev. 1: 167-195.
4. Coudriet, D. L., D. E. Meyerdirk, N. Prabhaker, and A. N. Kishaba.
1986. Bionomics of sweetpotato whitefly (Homoptcras Aloyrodidae) on
weed hosts in the Imperial Valley, California. Environ. Entomol.
5. Duffus, J. E. and R. A. Flock. 1982. Whitefly-transmitted disease
complex in the desert Southwest. Calif. Agric. 36. 4-6.
6. Greathead, A. H. 1986. Host Plants. Pages 17-26 in M. J. W. Cock,
Ed. Bemisia tabaci a literature survey. C.A.B. International
Institute of Biological Control. Silwood Park, England. 121 pages.
7. Hamon, Avas B. and Victor Salguero. 1987. Bemisia tabaci,
sweetpotato whitefly, in Florida (Homoptera: Aleyrodidae:
Aleyrodinae). Fla. Dept. Agric. and Consumer Services Div. of Plant
Industry. Entomol Circ. 292. 2 pp.
8. Lopez-Avila, A. and M. J. W. Cock. 1986. Economic Damage. Pages
51-54 in M. J. W. Cock, Ed. Bemisia tabaci a literature survey.
C.A.B. Thternational Institute of Biological Control. Silwood Park,
England. 121 pages.
9. Mound, L. A. 1962. Studies on the olfaction and colour sensitivity
of Bemisia tabaci (Genn.) (Homoptera: Aleyrodidae). Entomol. Exp.
et Applic. 5: 99-104.
10. Prabhaker, N., D. L. Coudriet and D. E. Meyerdirk. 1985.
Insecticide resistance in the sweetpotato whitefly, Bemisia tabaci
(Homoptera: Aleyrodidae). J. Econ. Entomol. 78 (4): 748-52.
11. Russell, L. M. 1975. Collective records of Bemisia tabaci
(Gennadius) in the United States. Coop. Econ. Insect Rep. 25-- (12