[compost_tea] FIRE ANT KILLING PROTOZOA FOUND IN 120 TEXAS COUNTIES

From: Tim Kiphart <kiphart_at_ev1.net>
Date: Mon, 22 Mar 2004 19:12:38 -0600

 A pretty radical discovery...

Subject: FIRE ANT KILLING PROTOZOA FOUND IN 120 TEXAS COUNTIES


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March 22, 2004
FIRE ANT KILLING PROTOZOA FOUND IN 120 TEXAS COUNTIES
Writer: Robert Burns, (903) 834-6191, rd-burns_at_tamu.edu
Contact: Dr. Forrest Mitchell, (254) 968-4144, f-mitchell_at_tamu.edu

    STEPHENVILLE - If imported fire ants dreamed - and who knows if they
do or don't - then a tiny protozoa could be their worst nightmare.
   Even better news: Texas A&M University System entomologists have
completed a survey that detected the protozoa in fire ant colonies in
approximately 120 of the 157 Texas counties where they have been found.
   Once a colony is infected, the protozoa debilitates the queen, the
workers and even the larvae. The disease shortens their the ants' life
spans and raises the mortality of sexual females.
   The tiny microorganism may not eradicate the fire ants but it has the
potential of changing it from a highly aggressive pest into one much less
competitive with native species, said Dr. Forrest Mitchell, entomologist
with the Texas Agricultural Experiment Station at Stephenville.
   Now that the survey is complete, the next step is to grow the protozoa
on culture mediums. If culturing is successful, the research might
eventually yield a product that would introduce the protozoa into fire ant
mounds in the form of a bait. Alternately, infected fire ants might be
introduced into areas where the protozoa is not present.
   But there are a lot of questions to be answered and problems to be
solved first.
   The first question, Mitchell said, is where did the protozoans come
from?
   Though there are several native species of fire ant, their stings pale
compared to their more aggressive cousin, the red imported fire ant, which
was accidentally introduced to the United States in the 1930s. Because it
lacks natural predators here, the red imported fire ant has spread to all
or portions of Florida, Georgia, South Carolina, Tennessee, Alabama,
Mississippi, Arkansas, Texas and Oklahoma. The species has become very
abundant, displacing many native ant species.
   Scientists have long known that one of the pest's natural enemies in
South America is Thelohania solenopsae, a microscopic organism related to
the amoeba.
   "It infects about 25 percent of the ants down there. It is one of the
natural pathogens, but the degree of its importance is hard to access,"
Mitchell said.
   The scientific community has been extremely cautious about introducing
the protozoa in the United States, however, not knowing what effect it
might have on the native ant species, such as harvester, carpenter and
leaf-cutting ants, Mitchell said.
   Because of these fears, studies of the South American protozoa were
done in labs under controlled conditions. Then in 1998, an U.S. Department
of Agriculture entomologist found an fire ant colony near Thorndale
infested with the protozoa.
   "Later, tests showed that the DNA of the Thorndale strain differed from
the South American strain," Mitchell said.
   The Texas A&M survey shows the protozoa has occurred naturally, without
human intervention. Questions still remain, however, before Mitchell is
comfortable with the idea of helping the protozoa propagate. It could be
that the protozoa was in North America all along, just waiting for the
fire ant to be introduced as a host? Or, was the protozoa itself an
emigre, hitching into the country with the South America fire ants? If it
was an emigre, did the protozoa evolve so its DNA now looks different from
that of the South American strain?
   If the protozoa is native to North America, then its further
introduction will not likely harm the native ant population. They are
already adapted to it.
   If it's not native,, helping it spread might not be a wise thing to do,
Mitchell said.
   These are crucial questions because ants play a critical role in the
ecological balance. The predatory types kill and eat many other insects,
both harmful and beneficial. Though small individually, collectively ants
can make a huge impact. Worldwide, a figure for ants comprising 15 percent
of all terrestrial animal biomass is not out of line.
   "No one really knows for sure what percentage ants constitute of the
animal biomass. But one thing is for certain. If you really want to
disrupt the ecosystem, disrupt the ants," Mitchell said.





 
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Received on Mon Mar 22 2004 - 20:49:34 EST

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