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Getting Atop Climbing Fern
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This moth, a female Cataclysta camptozonale,
is showing great promise as a biocontrol
for Old World climbing fern, an invasive
vine that’s winding its way across
Florida. The Australian native is the
first insect brought into the United States
to combat climbing fern.
(K9669-1)
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A team of two tiny moths might help
stop the spread of Old World climbing fern, an aggressive vine that's on the
march in central and south Florida. With further research, a third moth, a
hungry mite, a small beetle, and perhaps other hardworking organisms as well
may qualify to join the coterie of pint-sized weed-eaters.
Known to botanists as Lygodium microphyllum, Old World climbing fern
makes its way up stems and trunks of other plants, forming blankets of
light-green vegetation.
On the ground, climbing fern creates tough, spongy mats that can easily smother
grasses, low-growing shrubs, and small trees. Today, it infests more than
100,000 acres in Florida and shows no sign of slowing its advance. |
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Entomologist Robert Pemberton observes
invasive Old World climbing fern
overtaking cypress trees in southern Florida.
(K8958-6)
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ARS scientists based at research
laboratories in Florida and Australia are scrutinizing natural enemies of the
fern. They're searching the globe for promising organisms, then subjecting them
to rigorous tests in their laboratories.
Some of the studies are host-specificity experiments. They are designed to
determine whether the moths will munch on climbing fern alone and not harm
native ferns or other vegetation.
Other tests reveal whether top-ranked biological control agents—such as
the moths—will be effective in attacking the fern. To warrant the time and
expense invested in finding, shipping, studying, rearing, and releasing them,
every candidate biological control agent must be very good at what it does.
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Larvae, or caterpillars, of the
Cataclysta camptozonale moth feed on
leaves of climbing fern, weakening the plant.
(K9670-1)
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Investigations of the promising moths
Cataclysta camptozonale and Neomusotima conspurcatalis are under
way at the ARS Invasive Plant Research Laboratory at Fort Lauderdale and
Gainesville, Florida, and at the ARS Australian Biological Control Laboratory
in Indooroopilly, just outside of Brisbane. ARS operates the Indooroopilly
laboratory in conjunction with Australia's Commonwealth Scientific and
Industrial Research Organization, or CSIRO.
Climbing fern is native to Australia, South and Southeast Asia, and Africa. On
its home turf, the fern is not a pest, perhaps because its enemies keep it in
check.
Both of the fern-eating moths are about a half-inch from wingtip to wingtip.
C. camptozonale is bright white, with some spots and stripes on its
wings. |
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Scanning electron microscopy image of a
tiny mite of the genus Floracarus.
The mite is under study as a possible
biological control agent for Old World
climbing fern.
(K9668-1)
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N. conspurcatalis has
dark-brown wings that are edged with white and sprinkled with small, white,
boomerang-shaped markings.
C. camptozonale is nearing the end of testing, according to entomologist
Robert W. Pemberton, who is with ARS at Fort Lauderdale. Indoor
host-specificity tests in Florida encompassed 63 species of native and
cultivated ferns and closely related plants called fern allies, along with
citrus and five kinds of familiar vegetables.
Those tests indicated that the moth's slender, wormlike larvae prefer to eat
Lygodium fronds. Pemberton designed the studies and collected most of
the plants needed for testing in Gainesville. ARS entomologist Gary R.
Buckingham and colleague Christine A. Bennett of the University of Florida are
conducting the studies. |
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The male Cataclysta camptozonale moth
has darker brown markings than the
female, shown on the cover.
(K9669-2)
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Candidate Imported From
Australia
The insects used in the tests are descendants of those collected by researchers
with the Indooroopilly laboratory, located in subtropical Queensland on
Australia's east coast. Entomologist John A. Goolsby and coinvestigators there
gathered the C. camptozonale moth from climbing fern plants in
Queensland.
When the moth passed preliminary tests with climbing fern and 28 other fern
species, the Indooroopilly scientists sent about 250 moths to colleague
Buckingham in Gainesville for further study. C. camptozonale is the
first insect exported to the United States for possible use in combating Old
World climbing fern, according to Goolsby. He directs the Indooroopilly lab.
The Florida team will complete more tests before deciding whether to seek
federal and state permission to release the moth at climbing-fern-infested
sites in Florida. Those experiments will indicate whether the moth poses a
threat to ferns native to nearby countries in the Caribbean and Central and
South America. Pemberton ventured to the Dominican Republic and Argentina to
obtain several of those fern species for these critical analyses.
Related Moth Analyzed
The second and closely related moth, N. conspurcatalis, is receiving the
same intense scrutiny. Pemberton found the moth attacking climbing fern on an
island near Hong Kong during an expedition to find fern enemies in 1997.
Goolsby's team collected this same species of moth in Australia and put it
through a battery of host-specificity tests at Indooroopilly. The moth passed
those tests, so the Indooroopilly team sent a supply to Florida this year for
final testing. If both moths pass that muster, they should be able to be used
effectively together. And both have many generations of young per year, which
means that the vines could be under pressure from the moths nearly year-round.
If enough feeding occurs, the vines may die.
Three More Possibilities
Another fern foe looks promising too. It is a small moth that Alma Solis of the
ARS Systematic Entomology Laboratory in Beltsville, Maryland, and colleague
Shen-Horn Yen of London's Natural History Museum have identified as a member of
the Musotima genus. According to Goolsby's tests, the moth “appears
to be specific to Lygodium and not tolerant of temperatures below
32°F.”
The moth's cold intolerance is important because it means the insect is
unlikely to survive cold winters in the eastern and northeastern United States,
where a native fern and climbing fern relative called L. palmatum
occurs.
In addition to the moths, a microscopic mite is making its way through the
barrage of tests at Indooroopilly. CSIRO entomologist Tony Wright, stationed at
the Indooroopilly laboratory, found the mite on climbing fern during
expeditions to Indonesia, Malaysia, and Thailand. It has also been collected
throughout Australia, where the fern is native.
To learn more about the mite's biology, Wright and Goolsby are collaborating
with mite experts David Walter of the University of Queensland in Brisbane and
Sebahat Ozman, there from Trakya University, in Turkey.
The researchers have determined that the mite, a member of the genus
Floracarus, has a short life cycle—about 12 days when kept indoors
at 70°F. Female mites feed on young fern leaves, causing them to curl and
soften. Then they lay their eggs in the curl, where their young, called nymphs,
feed and develop on the soft tissue. The nymphs' feeding causes the leaves to
fall off, so the vine has fewer leaves to capture sunlight for the energy it
needs.
Tests showed that mite-infested ferns had one-fourth the growth of plants
sprayed with a miticide. Says Goolsby, “We're running the study for 2
years so we can examine the long-term effects of the mite on the fern.”
A petite beetle, brown and only about one-quarter inch long, might also become
an important member of the fern-fighting team. Wright found the insect,
Endelus bakerianus, during an expedition to Thailand.
The beetle is a leafminer, meaning that while in its caterpillar or larval
stage, it tunnels into the leaves to feed on them.
“We're just now starting host-specificity testing,” says Goolsby.
With luck, this little beetle might end up playing a big role in protecting the
Everglades.—By Marcia Wood,
Agricultural Research Service Information Staff and Jesús
García, formerly with ARS.
This research is part of Crop Protection and Quarantine, an ARS National
Program (#304) described on the World Wide Web at
http://www.nps.ars.usda.gov.
To reach the scientists mentioned in this story, contact
Marcia Wood, USDA-ARS
Information Staff, 5601 Sunnyside
Ave., Beltsville, MD 20705; phone (301) 504-1662, fax (301) 504-1641. |
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"Getting Atop Climbing Fern" was published
in the January
2002 issue of Agricultural Research magazine.
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