The Next Big Sting Fire ANTS from Brazil threaten to spread throughout California, with painful -- or deadly -- consequences
Monday, February 21, 2000
Palm Desert, Riverside County -- It looks utterly
inviting, this city-owned common of lush, green
lawn. It's the kind of place that's ideal for an
impromptu picnic, or maybe practicing chip shots.
Best resist that impulse, though, advises Mike
Flores, an inspector with the California Department
of Food and Agriculture -- unless your idea of fun is
running down the street screaming while swarms of
vicious insects repeatedly sting your flesh. To
illustrate, Flores breaks off a twig from a shrub and
excavates a small amount of finely granulated soil.
Suddenly the mound is boiling with glistening red
and brown ants. They're small
-- a few millimeters at best. But some are
significantly larger than others, and they're all in a
nasty mood.
They attack the stick in droves, simultaneously
biting it and impaling it with minuscule stingers
located at the rear of their abdomens.
The entire lawn is a teeming breeding ground for the
insects, says Flores.
``They completely infest this entire area,' he says,
indicating neighboring lots with a sweep of his arm.
The twig mugging is a pretty intimidating display,
especially when Flores explains what would happen
if the twig were a human arm.
``Each sting forms a pustule,' he said. ``The whole
arm could swell up. In bad cases, people require
hospitalization
-- or they may die.'
Say hello to the red imported fire ant, the latest
noxious beast to invade California. It joins the
mitten crab, starling, English sparrow, Eastern red
fox and a host of other exotic species that have
made the Golden State their home at the expense of
agriculture, native wildlife and human comfort.
Unless some magic bullet is found to stop them, the
ants could occupy much of California in coming
decades, though places with cold winters should be
safe because the insects shun the cold.
Given its mild climate, the Bay Area is by no means
immune to fire ant invasion.
Fire ants first showed up in California a couple of
years ago, when a few mounds were discovered in
Kern County near some wooden beehives. Apiaries
are a common hitchhiking device for the critters,
which have made their way north from southern
Brazil.
And Palm Desert is the front line of the fire-ant
wars. They've infested hundreds, perhaps
thousands, of acres of this tony desert resort, and
most experts think the situation will only grow
worse. The state Department of Food and
Agriculture has established an emergency office in
Palm Desert to deal with the invasion.
``They're in yards, golf courses -- even circuit
boxes, because they're somehow attracted to
electrical current,' says Brian Cahill, a plant
pathologist with the agriculture department.
There are several species of fire ant -- a generic
term for colonizing ants that sting to fend off
attackers or subdue prey -- including several native
to the United States.
But it is the red imported fire ant, Solenopsis invicta,
a species indigenous to parts of Brazil, Argentina
and Paraguay, that is the biggest pain.
For one thing, they pack the most potent sting of
any of the commonly encountered fire ants, a nasty
amalgam of formic acid and allergenic proteins that
can induce anaphylactic shock in a small percentage
of the human population.
And they are particularly fecund and opportunistic.
Red imported fire ants sometimes form ``polygyne'
colonies - interlocking mounds supported by 1,000
queens or more, each pumping out several thousand
eggs a day.
Such super colonies may conjoin with others,
ultimately sprawling over many acres of land in a
kind of ant megalopolis. In such circumstances,
there may be up to 700 eighteen-inch high mounds
per acre, each supporting several thousand workers
that swarm out of the nest and sting at the slightest
provocation.
Fire ants communicate through pheromones --
complex chemicals that are released and recognized
by all ants in the colony, each signifying a specific
imperative.
When a threat -- say a human arm -- is
encountered, the ants first rush out to investigate.
Sooner or later, one of the ants decides to bite,
releasing an ``attack' pheromone. This is picked up
by all the neighboring ants, which bite more or less
simultaneously.
Imported red fire ant colonies contain two types of
workers: tiny ``miners' that excavate soil, and
somewhat larger ``foragers' that hunt for food. Both
attack and sting when the nest is threatened. As a
colony ages, the queen produces more foragers
than miners, because most of the requisite
excavation is accomplished relatively early in a
nest's history.
Fire ants are loathed by farmers because their
mounds damage farm machinery. The ants also
consume vegetable seedlings, attack young
livestock and bedevil agricultural workers.
Plant nursery owners detest them because the ants
love to set up housekeeping in potted plants. Once
fire ants are discovered, nurseries are usually placed
under government quarantine, and owners must pay
big bucks to fumigate their stock before they are
allowed to sell it. So far, it appears that no ants
have spread to the Bay Area through untreated
nursery seedlings.
In suburban settings, fire ants mar household
landscaping and sting pets and gardeners, often
severely.
Small wonder that agricultural commissioners and
medical authorities view their appearance in
California with trepidation. They need only look to
the American South to see precisely how they don't
want things to go.
There, fire ants have thoroughly colonized nine
states, annually inducing more than 25,000 people
to seek medical aid for stings.
About a dozen Southerners die from fire-ant stings
a year, invariably from anaphylactic shock. Others
require skin grafting to recover completely from
severe attacks.
In North Carolina, fire ants are undermining roads
with their enthusiastic nest excavation. The state
now spends about $2,000 per mile of highway to
repair fire-ant damage, says Cahill.
Fire ants are now so ubiquitous in the South that
pest control agencies no longer attempt aggressive
control measures, concentrating most of their efforts
on public education and providing poisoned baits to
land owners who want to mount their own
campaigns.
Not only are fire ants easily dispersed by nursery
stock, bee hives, farm equipment and building
materials
-- they can also get around on their own. Several
times a year, each colony releases large quantities of
alates, as winged, fertile ants are known. The alates,
both male and female, fly into the air, mate in
mid-flight, then fall to the ground.
The males die, and the fertilized females shed their
wings and dig into the soil, where they lay the eggs
that will ultimately hatch into the first workers of a
nascent colony.
``The discouraging thing is that (alates) can disperse
more than a mile from their home nest,' observes
Cahill. ``They can also move by water -- they kind
of roll up into big balls surrounding the queen and
float down rivers,' he said.
Fire ants can have dire consequences even in the
water, as evidenced by a huge die-off of trout in a
creek near San Antonio a few years ago.
When authorities dissected the fish, they found their
stomachs were chock-full of fire ants. The trout
probably died from both gastricly absorbing the
venom and being stung internally.
Fire ants need water, making for an ironic situation
in the California desert. The Palm Desert/Palm
Springs area, of course, blooms with golf courses
and landscaping thanks to lavish irrigation. In other
words, the ants are attracted to precisely the places
that people are most likely to frequent.
The best way to control fire ants is with poisoned
bait. The worker ants partially digest the bait and
pass it down as liquid, from ant to ant, until it
reaches the queen. When the queen dies, the colony
dies.
But effective fire-ant baits contain relatively
long-lived poisons, says Cahill, and great care must
be taken to ensure that groundwater and creeks are
not contaminated. That may ultimately limit -- and
minimize the effectiveness of -- control efforts.
``Monitoring is already being done in Newport Bay
and the Irvine Channel (in Orange County) because
of contamination concerns,' Cahill said.
Research is also under way on the phorid fly, a
minute insect that lays its eggs in the heads of fire
ants. When the eggs hatch, the larvae feast heartily,
eventually decapitating their hosts. Phorid flies
effectively control fire ants in South America, but it
is unknown if they will flourish here. Because they
are limited by climate, meanwhile, fire ants won't
explode willy-nilly throughout the state. Regions that
post temperatures of 10 degrees F or lower will
remain uncolonized
-- unless the ants somehow acclimate to frigid
weather or hybridize with native ants. Either
possibility is not completely out of the question.
And as for the warm parts of the state? Hope for
the best, certainly -- but expect the worst.
Sometimes life simply involves unpleasant
accommodations.
``I think the Coachella Valley (including Palm
Desert) and Orange County are already lost
causes,' sighs Oesterlein. ``They're just too well
established, and control is too difficult.'
FIRE ANT MOUNDS
Unlike native ants, fire ants do not build mounds
with central openings. Instead, the ants rely on an
extensive tunneling system and multiple routes to
gain access to their mounds. It is thought that the
tunnels act as acoustic amplifiers, aiding in
communication by transmitting sounds associated
with stress when the nest is under attack.
Colonies house 100,000 or more ants.
Mounds range in size from a few inches to 18
inches tall.
THE ATTACK
Fire ants communicate through sound, and also
through pheromones -- complex chemical
compounds that elicit specific responses. After
swarming over an intruder, some of the fire ants
sting, immediately inducing their neighbors to follow
suit through the release of an ``attack' pheromone.
Ant stings cause a painful sore and may result in
severe reactions by those who are allergic to the
venom.
The fire ant uses its mouth to lock its body into
position as it pierces the skin with its stinger.
INFESTATION IN THE UNITED
STATES
Red imported fire ants originated in South America.
They were transported to the southern United
States several decades ago, presumably in soil used
as shipping ballast. They have since infested nine
states and were recently discovered in California.
Control measures are likely to prove futile in
eradicating them in this state, though strict
quarantines may help control their spread.
Sources: Calif. Dept. of Food and Agriculture,
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