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Copyright 2005, Board of Trustees, University
The Citrus Blackfly
Joseph L. Knapp, Robert V. Dowell, Ronald H. Cherry
George E. Fitzpatrick and James A. Reinert
Florida Cooperative Extension Service Institute of Food and Agricultural Sciences
University of Florida, Gainesville, FL 32611 John T. Woeste, Dean for Extension
THE CITRUS BLACKFLY IN FLORIDA
By Joseph L. Knapp, Robert V. Dowell, Ronald H. Cherry,
George E. Fitzpatrick and James A. Reinert
The citrus blackfly (CBF), Aleurocanthus woglumi Ashby, is not
black nor is it a true fly, but is a member of the whitefly family,
related to scales, mealybugs, and aphids. It is of Asian origin and
was first found in the New World in Jamaica in 1913. Since then it
has spread to most citrus growing regions of the western
Since this discovery in Jamaica, CBF has been considered a threat
to the citrus industry of Florida in view of the location of infested
areas and the frequent interception of infested plant material at
Florida's ports of entry.
CBF was first discovered in Florida in 1934 on Key West where it
was confined to citrus and mango located in dooryards. This infesta-
tion was eradicated by 1937 through the use of oil sprays. A second
infestation was discovered in the Ft. Lauderdale area on January
28, 1976. Surveys conducted by state and federal regulatory person-
nel soon showed that virtually all the urban areas of Broward
County and the adjacent portions of Dade and Palm Beach Counties
also were infested with CBF. Since 1976, CBF infestations have
been detected in several other citrus producing counties of Florida.
Extensive research has been conducted on the CBF by the Univer-
sity of Florida IFAS, and USDA-SEA. This work has resulted in
the biological control of the pest to the extent that CBF should pose
no economic threat to the Florida citrus industry as long as this
biological control is not disrupted.
Knapp is Extension Pest Management Specialist, University of Florida, Agricultural
Research and Education Center, Lake Alfred. Dowell and Cherry are Assistant Research
Scientists (Citrus Blackfly), University of Florida, Agricultural Research Center, Ft. Lau-
derdale. Fitzpatrick is Assistant Professor, Ornamental Horticulture, University of Flori-
da, Agricultural Research Center, Ft. Lauderdale. Reinert is Professor, Entomology (Turf
and Ornamentals), University of Florida, Agricultural Research Center, Ft. Lauderdale.
Figure 1. Infested leaf showing egg spirals, immature forms, and adults.
Female CBF lay their eggs in distinctive spiral-like patterns on
the underside of leaves (Fig. 1). Each female CBF lays two to three
such egg spirals (28-34 eggs/spiral) usually within three to four days
after their emergence. The first stage or instar hatches from the egg
in 9-50 days depending upon temperature. This is the only mobile
immature stage. Generally they settle and feed in close proximity to
the egg spiral. A small percentage of these first instar nymphs,
however, may move several inches away from the egg spirals in
three to four hours.
The first nymphal instar that emerges from the egg is rather
elongate and egg shaped, being 0.012 in. long and 0.006 in. wide (0.3
x 0.15 mm), whitish in color, with reddish eye spots, short antennae
and short legs. Within four hours they become uniformly blackish in
The early second instar (0.016 x 0.008 in., or 0.41 x 0.2 mm), is
whitish in color, flattened, with the eye spots quite prominent.
Within three to four hours after molting, the second instar becomes
dull black with the exception of a large circular spot on the front
part of the back, which remains a dull green. Spines are numerous
The third instar is similar in color to the second with the spines
being more numerous and stouter than in the second. Sexes can be
distinguished for the first time in this instar, the males being
smaller than the females.
The fourth instar is distinctly egg-shaped with the front being the
smaller end. This instar is decidedly convex, with a prominent ridge,
and is covered with numerous long, stout spines. Females are much
longer (0.05 x 0.03 in. or 1.24 x 0.71 mm) than the males (0.04 x 0.02
in. or 0.99 x 0.61 mm). A white wax is secreted around the margins
of the body, the males usually secreting noticeably more than the
The fourth instar molts and becomes an adult. The time taken for
normal emergence is from 15-30 minutes. Young adults often fall to
the ground where they die or fall victim to predators.
When adults first emerge, the greater part of the body is bright
brick-red in color, with the front of the head pale yellow, the anten-
nae and legs whitish, and the eyes a deep red or reddish brown.
Within 24 hours after emergence, the insects become slaty blue in
appearance, with the colorless spots on the wings forming what ap-
pears to be a white band across the middle of the back when at rest
Figure 2. Adult citrus blackfly.
Adult CBF can live for up to 14 days but most eggs are laid in the
first four days.
In Florida, there is a possibility of three to four generations per
year depending upon the temperature.
CBF and its natural enemies can survive any temperature ex-
tremes found in citrus growing regions of Florida.
ADULT N" --
NYMPH or FIRST
LIFE CYCLE OF THE
CITRUS BLACKFLY IstMOLT
Aleurocanthus woglumi (Ashby)
Table 1. Development of the immature stages of CBF at selected
constant temperatures in days:
OC OF Eggs 1st 2nd 3rd 4th Total
None None None
16 60 97 73 55 70 272 567
21 70 22 17 13 16 63 133
27 80 13 9 7 9 36 74
32 90 9 7 5 6 25 52
CBF prefers to oviposit on citrus, mango, kumquat, and pink
trumpet. Citrus and mango appear to be the most preferred host for
Table 2. Average number of egg spirals laid on potted plants
by CBF in dooryard exposures, and ability of plants
to support CBF populations.
Ability of host
Avg. no. egg plant to support
Plant spirals/plant CBF population
Citrus 10.0 Yes
Mango 7.5 No
Pink trumpet 7.3 No
Kumquat 6.7 No
Wampi 2.8 Yes
Loquat 2.5 No
Ardisia 0.3 Yes
Black sapote 0.1 Yes
Surinam cherry 0.1 Yes
Avocado 0 No
All Citrus spp. tested were equally attractive to egg laying CBF
and all supported complete development of the insect.
There are two routes by which CBF can disperse:
1. adult flight 0.25 to 0.37 mile (400-600 meters) per genera-
2. transportation by man through the movement of infested
plants or leaves. The latter probably accounts for its widespread
distribution in Florida.
Damage to Tree
Infestations of immature CBF can damage a plant in two distinct
ways. The first is through the direct feeding of nymphs on the
leaves. The second is through the excretion of honey-dew on which
various sooty mold (fungi) develop. Under moderate to heavy in-
festations, (Fig. 4) the leaves will be black on the underside due to
the presence of immature CBF and black on the upper surface due to
the presence of sooty mold (Fig. 5).
Research has shown that a nitrogen level of 2.2% is necessary in
plant tissue for successful fruit set in oranges. Fifty to one hundred
nymphs per leaf are required to reduce the nitrogen level below this
amount. Data indicate that CBF poses no economic threat to citrus
trees unless densities exceed 75/leaf or the trees already have other
severe stress problems.
Figure 4. Citrus leaf showing heavy citrus blackfly infestation.
Figure 5. Above: Citrus blackfly lower leaf surface. Below: Sooty mold -
upper leaf surface.
Leaves infested with live CBF are consistently more common on
the lower half of citrus trees. CBF egg spirals tend to be clumped on
individual leaves and in turn, infested leaves also tend to be
clumped on the tree. Thus, at economically damaging levels, CBF
infested leaves are very easily seen. Highly infested leaves will also
be covered by sooty mold. Note, however, that sooty mold will also
develop on honey-dew excreted by other whiteflies, aphids, scales,
Since CBF dispersal and population buildup are slow, two visual
inspections per year should suffice for their detection. In any area
north of Palm Beach County, observations should be made in June
and September. In those areas south of Palm Beach County, look in
May and August. Any leaves believed to be infested with CBF
should be taken to your County Extension Office for examination.
Three species of parasitic wasps were received from Citrus Insects
Research Laborartory, USDA-SEA, in 1976. They were Amitus
hesperidum Silvestri, Prospaltella opulenta Silvestri and Pros-
paltella clypealis Silvestri. The population of CBF in Broward
County has been reduced 98% by these introduced parasites.
Various species of spiders, lacewings, and ladybeetles feed on the
CBF. Although these predators can kill up to 80% of the CBF, they
alone are not capable of controlling CBF populations. This is
because the CBF lays enough eggs to more than compensate for the
loss of offspring.
CBF is not attacked by the native Aschersonia spp., the fungus
which aids in the control of other whitefly species on Florida citrus.
CBF is currently under complete biological control in Florida
through the combined action of the parasites, A. hesperidum and P.
opulenta. The CBF population that remains is far below the level
that can result in reduced fruit production.
Biological control of this pest is compatible with existing pest
management practices on Florida citrus.
The Florida Citrus Spray Guide (Extension Circular 393-E) con-
tains a wide range of materials recommended for the control of in-
sects, mites, and phytopathogenic diseases. Many of the insect-
icides included in this guide for controlling other pests provide ac-
ceptable levels of control for CBF. The following pesticides have
been evaluated and result in 90% or greater mortality of the CBF:
Diazinon; Ethion; Trithion; Malathion; Supracide; Azinphos-methyl
(Guthion); and FC-435 spray oil.
The most important questions that must be addressed when con-
sidering chemical control impact on CBF populations are the short
and long term effects of the sprays on the natural enemy complex of
CBF. To date, Malathion, Supracide, Chlorobenzilate, Benlate, and
FC-435 spray oil have been evaluated. These should not cause a
resurgence in a CBF population if used in accordance with the
Florida Citrus Spray Guide.
This public document was promulgated at a cost of $1,070.,
or 7.1 cents per copy to inform growers of citrus, tropical frl
and ornamentals about the citrus blackfly. 2-15M-80
COOPERATIVE EXTENSION SERVICE, UNIVERSITY OF FLOR-
IDA, INSTITUTE OF FOOD AND AGRICULTURAL SCIENCES,
K. R. Tefertlller, director, In cooperation with the United States
Department of Agriculture, publishes this Information to further the
purpose of the May 8 and June 30, 1914 Acts of Congress; and is
authorized to provide research, educational Information and other
services only to individuals and Institutions that function without regard to r.
sex or national origin. Single copies of Extension publications (excluding 4 -H -
publications) are available free to Florida residents from County Extensk
Information on bulk rates or copies for out-of-state purchasers Is available fr
HInton, Publications Distribution Center, IFAS Building 664, University of.
Gainesvllle, Florida 32611. Before publicizing this publication, editors should
this address to determine availability.