Fly From Amazon
Jungle Could Be Next Weapon Against Water Weed
By Jim De
March 1, 2000
WASHINGTON, Mar. 1--A tiny,
newly discovered Amazonian fly that attacks water-hyacinth weeds has for the
first time been reared in large numbers. "This is our researchers' latest
step to building a new team of natural enemies to stop water-hyacinth, a nasty
aquatic weed," said Floyd P. Horn, administrator of
USDA's Agricultural Research Service.
Dense water-hyacinth mats infest hundreds of ponds, lakes and streams in
California, Hawaii and throughout the south from Texas to the Carolinas. The
plant is native to South America. The mats rob water from drinking and
irrigation supplies, block boat travel and clog water-pumping stations. They
also damage water quality, blocking light and oxygen and slowing the water
flow. And they choke out other plants--and the fish and other animals that rely
on these plants or on access to open water.
The 1.5-millimeter fly, discovered last year by
ARS researchers, is a new species of
Thrypticus. Immature flies feed inside the weed's petioles, the tiny stalks
that attach leaves to stems. In addition, the flies' tunneling may enable
microbes to enter and further weaken or kill the plants.
"These flies--and other new species the scientists discovered in the
upper Amazon basin--could become the first new insects imported to attack
water-hyacinth in about 25 years, Horn said. "Biological control
with insects and other natural enemies, such as fungi, is essential to a
long-term solution. Today's primary weapons--herbicides and mechanical
removal--can be costly and are often ineffective.
ARS entomologist Hugo Cordo and colleagues found the new species last April
near Iquitos, Peru. Cordo leads ARS' South American Biological Control
Laboratory in Buenos Aires, Argentina. ARS is USDA's chief scientific wing.
In early to mid December, Cordo's research team released several hundred
adult Thrypticus water-hyacinth petiole mining flies on water-hyacinth
plants in a 6-foot-square cage outside the Buenos Aires lab. The flies mated,
and large numbers of their adult offspring began appearing in January.
"With luck,"Cordo said, "Thrypticus might be ready to
import in two or three years" for testing in an ARS quarantine laboratory
In the 1970's, three South American insects were found and tested in
Argentina and imported and released in the U.S. by ARS entomologists Neal
Spencer and Ted Center, who was with Cordo on the 1999 expedition. "Today
these insects help check water-hyacinth in the U.S. and more than a dozen other
countries," Horn said. "But having a more diverse crew of natural
enemies should increase our success against this invasive weed species."
In the Amazon, insects and microbes put water-hyacinth under stress. This
controls the mats expansion. But the weed has escaped to many countries
where these natural enemies aren't present. Visitors attracted by the plant's
lush leaves and blue-to- lavender flowers have often taken it home as an
ornamental. That's apparently how it reached the U.S. in the late 19th century.
The Iquitos region may be the world's richest source of natural
enemies of water- hyacinth, Cordo said in the March issue of ARS
Cordo's expedition colleagues were Center, who leads the ARS
Plant Control Research Unit in Fort Lauderdale, Fla., Martin Hill of South
Protection Research Institute, and Harry Evans and Djami Djeddour of
CABI Bioscience in
England. They searched 180 kilometers of the upper Amazon River and the Ucayali
and Marañon Rivers that converge to form it. They collected hundreds of
natural enemies and plant samples at 30 sites over 7 days.
Cordo's research team has discovered 11 new insect species on water-hyacinth
and its relatives in Peru and northern Argentina since 1996. They include six
Thrypticus species, three Taosa plant hoppers and two
Megamelus plant hoppers. Researchers are studying the insects' biology
and behavior and screening them to identify the best candidates for biological
control. They are also making sure water-hyacinth is the only plant attacked.
"Along with crops, this means testing ornamentals and plants in natural
settings," Cordo said.
Scientific contact: Hugo Cordo, ARS South American Biological Control
Laboratory, Hurlingham, Argentina, phone/fax 54-11-4662-0999,
D. Center, ARS Aquatic Plant Control Research Unit, Fort Lauderdale, Fla.,
phone (954) 475-0541, ext. 103, fax (954) 476-9169,