<br><font size=2 face="sans-serif">Forwarding an interesting nugget of
info on this topic.</font>
<br>
<br>
<br><font size=1 color=#800080 face="sans-serif">----- Forwarded by Patricia
De Angelis/ARL/R9/FWS/DOI on 05/18/2007 06:20 PM -----</font>
<br>
<br><font size=2><tt>Yes, but how about the "duck Alzheimer's"
which appears to be associated<br>
with hydrilla. Also, not all scientists agree the Potomac hydrilla<br>
infestation is so innocuous.<br>
<br>
There are possible redeeming virtues to a lot of things. The dose
makes<br>
the poison is a statement sometimes heard from toxicology.<br>
<br>
Volume 20 | Issue 5 | Page 59 | Reprints | Issue Contents<br>
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1 comment<br>
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<br>
COLUMN<br>
By Jack Woodall<br>
Space Invaders Are Here<br>
Guess what? They're little and green!<br>
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<br>
I wonder why people began imagining that space invaders were green. Perhaps<br>
it was because humans had already appropriated most of the other colors:<br>
black, white, khaki, red, yellow, and blue. The ancient Brits painted their<br>
naked bodies blue with woad, so they say, but that was before football
fans<br>
started painting themselves in the colors of their teams. Now you can see<br>
green people rooting for Brazil, but they have a yellow stripe also.<br>
<br>
<br>
Be that as it may, the color of the invaders I am talking about is due
to<br>
chlorophyll; they are plants, not humanoids, and they do not come from<br>
outer space, but from one part of the globe to invade the space of another.<br>
Classic examples are the Nile cabbage (Pistia stratiotes), responsible
for<br>
blocking navigation over long stretches of the White Nile in the southern<br>
Sudan, has turned up in the Amazon. In revenge, the South American water<br>
hyacinth (Eichornia crassipes) - with its lilac flowers and gas-filled<br>
bladders that give buoyancy to drift down rivers and foul the beaches of<br>
Rio de Janeiro after torrential rains - has invaded the Nile.<br>
<br>
<br>
I want to report on two much more insidious green threats, with the<br>
appropriately alien names of kudzu (Pueraria montana var. lobata) and<br>
hydrilla (Hydrilla verticillata). Kudzu is a broad-leaved Asian vine,<br>
imported to the United States a century ago by immigrant farmers to grow
as<br>
cheap fodder for their cattle. It has spread out of control across enormous<br>
areas of the country, overgrowing and strangling every tree, bush, plant,<br>
or even object in its path (see the images at www.jjanthony.com/kudzu ).<br>
<br>
<br>
The damage does not stop there. Kudzu is host to a serious crop pest. The<br>
fungus that causes soybean rust (Phakopsora pachyrhizi) was first<br>
identified in Japan in 1902 and took a century to cross the Pacific,<br>
reaching South America in 2000. In 2004 Hurricane Ivan picked up spores<br>
from there and dropped them over nine southern states of the United States.<br>
Once there, they not only infested soybean fields, but also found a<br>
congenial alternate host: kudzu. As a result, no matter how much fungicide<br>
farmers spread on their soybean fields, the rust will be hiding in kudzu<br>
leaves ready to make a comeback. But in a nice twist, weed-control groups<br>
are growing the fungus that causes wheat rust, another crop pest; the<br>
fungus is rubbed into cuts in the kudzu stems to kill the plant.<br>
<br>
<br>
The other alien threat was discovered when American bald eagles (Haliacetus<br>
leucocephalus) and coots (Fulica americana) began to flop around in circles<br>
and show brain damage - I have no idea why it wasn't called mad bird<br>
disease - and to die in numbers on some Arkansas lakes. Between 1994 and<br>
2002, at least 100 eagles and thousands of coots died at 11 lakes between<br>
North Carolina and Texas. The cause was traced to a neurotoxin in the<br>
water. But what was the source of the poison, and why did it affect mostly<br>
those two species?<br>
<br>
<br>
It turns out that the neurotoxin is connected to hydrilla, an invasive<br>
species of water plant. Hydrilla was imported into the United States in
the<br>
1960s from its native Africa, Australia, and parts of Asia by the aquarium<br>
industry to prettify fish tanks. Inevitably, it escaped when aquarium<br>
owners emptied their tanks into the environment, and it now totally covers<br>
the surface of many lakes in Arkansas, Florida, and other states — 10,000<br>
acres in South Carolina alone.<br>
<br>
<br>
The damage does not stop there. Hydrilla attracts a blue-green<br>
cyanobacterium, of a species previously unrecorded in the United States,<br>
which flourishes on its slender fronds. Cyanobacteria as a class produce<br>
deadly toxins - not, I hasten to add, out of pure malice, but as an<br>
unintended consequence of getting rid of unwanted products of their<br>
metabolism. Vegetarian water birds such as coots and many ducks feed on
the<br>
plant, sicken from the toxin and die. Eagles find the sick birds easy prey,<br>
feed on them, and die in their turn - a classic food-chain disaster just<br>
like that which led to the banning of DDT.<br>
<br>
<br>
So beware of little green alien invaders. Chop down the kudzu on your land<br>
and when you empty your fish tanks, bury or burn the plants.<br>
<br>
<br>
Jack Woodall is director of the Nucleus for the Investigation of Emerging<br>
Infectious Diseases in the Institute of Medical Biochemistry at the Federal<br>
University of Rio de Janeiro, Brazil.<br>
<br>
jwoodall@the-scientist.com<br>
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Comment on this article<br>
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<br>
comment:<br>
Space Invaders Are Here<br>
by kate austin<br>
<br>
[Comment posted 2007-05-17 19:18:02]<br>
<br>
<br>
Kudzu covers over seven million acres in the South. Why not harvest it
and<br>
use it to produce cellulosic bioethanol for fuel? No need for chemical<br>
fertilizers or arable land needed for crops.<br>
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<br>
<br>
Alan V. Tasker, Ph.D.<br>
National Noxious Weed Program Manager<br>
<br>
USDA Animal & Plant Health Inspection Service<br>
Plant Protection & Quarantine<br>
Emergency and Domestic Programs<br>
Invasive Species & Pest Management<br>
<br>
(301) 734-5708<br>
Fax (301) 734-8584<br>
<br>
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