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Asian
Cycad Scale
(Aulacaspis yasumatsui)
Dave Palmer & JoAnn Hoffman
Hillsborough County Extension
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| The
problem...
Asian
cycad scale originates in Thailand and southern China. It is believed to
have been accidentally introduced into Florida through the legal
importation of cycads. Infestations of this scale insect have been moving
rapidly across the state since this pest was discovered in the mid 1990's
near Miami. (Hamon, 2000)
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Photo by Doug Caldwell
Click on the
picture to enlarge |
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How do I know if I
have
Asian cycad scale?
There are 2 ways to know if the scale on your sagos is Asian cycad scale.
1) Look at the insect under a
microscope and compare to the
image above of
the males and
female.
2) Compare the appearance of your
plant with the photos on
this site.
Click Here
to go to the photo page.
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This scale is known as cycad Aulacaspis scale, or
Asian cycad scale. The family of plants affected is called cycads. This
family includes king and queen sagos, cardboard palms, and coonties among
others.
At this point, only the sagos appear to be
affected. Cardboard palms and coonties have been relatively unaffected.
Although sagos give the appearance of palms, they are actually unrelated to
palms. Asian cycad scale has been observed on several other cycads, but does
not attack them as severely. A list of other species of cycads that are
reported to be attacked are listed at the Featured Creatures file at:
http://creatures.ifas.ufl.edu/orn/palms/cycad_scale.htm |
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In general, scale insects hatch into a "crawler" stage capable
of movement. When they find a suitable spot on a plant, they insert their
mouthparts, called a stylet - (much like a straw), into the plant and
start feeding. Shortly afterwards they begin to create a covering over
themselves. They will stay this way until they die.
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Photo by Doug Caldwell
Click on the
picture to enlarge |
Photo by Holly Glen
Click on the
picture to enlarge |
The
unusually dense populations and rapid spread of Asian cycad scale suggests
it is an exotic invasive and has few, if any natural enemies. This pest
appears to be spread short distances by wind dispersal of crawlers and
longer distances by transport of infested plants. (Weissling,1999) If left
untreated, this pest will kill its plant host.(Howard,1999)
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At its worst, an infestation of the Asian cycad scale can completely coat
a medium-sized sago within months and kill it within a year. (Howard,1999)
The scale can eventually form several layers and include a high proportion
of dead insects as well as live scale insects. Heavy infestations can
include up to 3000 scales per square inch in several layers. (Weissling,
1999)
The
Asian cycad scale is unusual in that it can also infest the roots of
cycads. These scales have been observed at depths up to 24 inches. (Weissling,
1999)
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Photo by Dave Palmer
Click on the
picture to enlarge |
Photo by Holly Glen
Click on the
picture to enlarge |
Is there a
solution?
In the longer term, the
ideal solution is one or more natural predators / parasites. Researchers
at USDA are currently rearing two insects to serve in this role. One is a
predatory beetle and one is a parasitic wasp. The biological approach will
not be quick fix as it may take several years for the predator populations
to increase to the point they can truly be helpful. Many counties across
Florida have begun to release parasitic wasps including Hillsborough
County in 2002.
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| One
solution that has proven somewhat effective, especially on smaller sagos is
to simply spray the plant with a hard stream of water from a hose (2003
Mannion). Done regularly and thoroughly this technique can at the least,
slow the pest down drastically. The
latest research (2003 Mannion) indicates that many products sold for the
control of scale work effectively on the Asian cycad scale. Horticultural
oils, (Ultrafine, summer oil, volck oil, dormant oil, etc), fish oil (not
fish emulsion) and malathion-in-oil all yield good results. Contact
pesticides, such as Malathion, kill insects by touching them. Systemic
insecticides, such as those with the active ingredients acephate, dimethoate,
disyston and imidacloprid, move into the sap system of the plant. The
insects are then poisoned when they feed on the sap of the plant. Research
shows that imidacloprid is not very effective on Asian cycad scale. A new
and effective treatment option is an insect growth regulator called
Distance. Due to the high cost of Distance it’s primarily a commercial
product.
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Photo by Holly Glen
Click on the
picture to enlarge |
How
can the Asian cycad scale
be controlled?
1) The
long-term solution is to find, raise,
and release predator / parasites. This is
being done by the USDA, DACS, and
IFAS.
2) The short term solution is to control the
pest on as many plants as possible.
a) The first step is to
treat the plants to
reduce the
populations of the scale.
b) The second step is to treat the plants
preventively until
the predator
population can grow
to the point that
the scale is controlled
naturally. |
Dimethoate, sold under various brand names, such as
Cygon, has been shown effective on this pest, but production of this
chemical has been discontinued. Stocks on this product are slowly being used
up and this option may not be around much longer.
Several new and effective treatment options have
recently been introduced. One is an insect growth regulator called Distance.
The active ingredient in Distance is pyriproxyfen. Another recent chemical
introduction is Safari. The active ingredient in Safari is dinotefuran.
Safari is available through stores that specialize in selling pesticides to
commercial applicators. It is not available in homeowner sized quantities at
this time, therefore is very expensive per package. However, the cost per
application becomes more reasonable if the effort required for protection is
decreased and the protection itself is increased. The active ingredient in
Safari is very water soluble making appropriate pesticide protective
equipment essential.
Dimethoate, sold under various brand names, such
as Cygon, has been shown effective on this pest, but production of this
chemical has been discontinued. Stocks on this product are quite limited, if
available at all.
We recommend using either horticultural oil or
Organocide as they appears to be quite effective with minimal disruption of
beneficial insects.
Be cautious of spraying any chemical in the heat
of the day, especially to any new growth that might be present. Spraying
earlier in the morning or later in the evening will help avoid damage.
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In the research that has been done, it was noted that within 21-35
days of hatching, Asian cycad scale females could begin laying eggs in
warmer weather. (Hamon, 2000) To prevent new generations of scale from
hatching and to bring this pest under control, spray every other week in
warmer weather (above 70o F) and once a month in colder weather
(below 70o F).
Make
sure the spray application is very thorough. Best
results are obtained using a fine spray, so pump-up sprayers using
adequate pressure to get into the nooks and crannies are preferable. Any gaps in coverage allow
the population to rebound quickly. Nearby infested plants can also spread
the scale back to plants that have been treated.
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Photo by Dave Palmer
Click on the
picture to enlarge |
Photo by Holly Glen
Click on the
picture to enlarge |
Spray the cycad down hard with a garden hose
to loosen the dead scale occasionally. Preventative treatments can be
either every other week or once a month (remember to be thorough) This
should keep the sago safe while biological controls gain momentum. Don’t
forget to treat the soil under the sago fronds at the same time you’re
treating the fronds. The research does not indicate how often to treat the
soil, but every other month should suffice.
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Systemic chemicals with active
ingredients like acephate, dimethoate, disyston and imidacloprid have
yielded mixed results. These systemic chemicals may also interfere with
the establishment of the predatory insects, (Howard, 2003) so they should
be used only in severe infestations and then only on a limited basis,
switching to oil or malathion-and-oil soon after.
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Photo by Holly Glen
Click on the
picture to enlarge
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Photo by Doug Caldwell
Click on the
picture to enlarge |
Other
factors...
Some people are suggesting that the situation
is hopeless and the only solution is to dig up all sagos and destroy them.
This perception runs contrary to the facts. Asian cycad scale is more
difficult to control than the typical scale because it has no natural
enemies, can move on the wind and can live on the roots of plants.
However, it is still just a scale and can be controlled in much the same
way as other scale insects. It takes more effort, but it can be done.
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| For
severe infestations, one option might be to remove all the fronds from the
sago before beginning chemical application. This is not recommended as
standard treatment - only on severe infestations. Removal of the fronds
allows the chemical application to be more thorough as treatment of the
fronds, both top and bottom can be eliminated and more attention focused
on the trunk and roots. |
Photo by Dave Palmer
Click on the
picture to enlarge |
Photo by Dave Palmer
Click on the
picture to enlarge |
At this
point in time, the pest is everywhere in Florida. There is really no point
in bagging the fronds and other clippings in plastic bags. That practice
will not slow the pest down in any way. Simply set the clippings out with
your other landscape debris. |
| The bottom
line...
All is
not lost. This is just a scale insect, although it’s a tougher one to
control than we’re used to. The hope is that once a predator / parasite
population is established, we’ll have to do no more chemical control
than before Asian cycad scale reared its ugly head. In the meantime some
sagos that are not cared for properly will die.
Get
the word out to your friends, neighbors and co-workers about proper
treatment options. We’ll have to work together to get through this. Remember the key is to treat thoroughly.
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Photo by Dave Palmer
Click on the
picture to enlarge |
References
Hamon, A., Cycad aulacaspis scale. Aulacaspis
yasumatsui, (2000) DACS
website, Entomology Section [On-line] Available:
http://doacs.state.fl.us/~pi/enpp/ento/aulacaspis.html
Howard. Update on Management Methods for New Scale Insect Pests. (2003)
Personal correspondence.
Howard, Hamon, Mclaughlin, Weissling and Yang. Aulacaspis yasumatsui
(Hemiterea: Sternorrhyncha: Diaspididae), a
Scale Insect Pest of Cycads
Recently Introduced into Florida (1999) Florida
Entomologist [On-line] 82 (1)
[Online] available http://www.fcla.edu/FlaEnt/fe82p14.htm
Weissling, Howard & Harmon. Cycad Aulacaspis Scale, Aulacaspis
yasumatsui
Takagi, UF/IFAS publication EENY-096, 1999.
[Online] available:
http://edis.ifas.ufl.edu/IN253 |
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and Agricultural Sciences (IFAS) is an Equal Employment Opportunity -
Affirmative Action Employer authorized to provide research, educational
information and other services only to individuals and institutions that
function without regard to race, color, sex, age, handicap or national
origin. U.S. Dept of Agriculture, Cooperative Extension Service,
University of Florida, IFAS, Fla A & M University Cooperative
Extension Program, and Boards of County Commissioners cooperating. |
