810-Lancaster Fanning, Saturday, February 22, 1992
BELTSVILLE, Md. We
have met the enemy, and it has six
legs.
In the Battle of Southern Cali
fornia, it is the tiny sweet-potato
white fly, which devasted the reg
ion’s fall vegetable crops the
latest struggle in the long-running
war between humans and insects
over food.
The news from the front is not
all good.
“I guess the insects are win
ning,” concedes Douglass R. Mill
er, head of research for the Syste
matic Entomology Laboratory at
theU.S. Agriculture Department’s
research center here.
As much as 95 percent of the
fall melon crop in California’s
Imperial Valley was lost last year
to swarms of white flies so thick
that they plastered windshields
and lodged between farmworkers’
teeth.
Other crops were savaged by
the hungry creatures as well: cit
rus fruits, grapes, sugar beets, let
tuce, cauliflower, broccoli,
squash, cabbages and carrots.
With winter settled in and the
insects retired from the field, sci
entists are using the cease-fire to
figure out what to do next. Their
first job has been to determine
what they’re up against.
“We suspect the white fly was
introduced into the United States
from somewhere else, and has no
effective natural enemies here,”
Miller tells National Geographic.
“There is also a remote possibility
that it’s something that changed
into a whole new biotype once it
got here, though we doubt that in
this case.”
A new biotype would be an
insect that belonged to the same
species (that is, it could mate with
others and produce offspring) but
would have different biological
characteristics because of muta
tion or reorganization of genetic
material.
These characteristics could be
passed to successive generations,
resulting in a new breed of insect
that is ii '.rvious to existing
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The pistol on Utah farmer Tim Nlunns' hip does him little good as migratory gras*
shoppers descend upon him and some recently baled hay. in the age-old competition
with ineects for food, nature sometimes comes to the aid of humans by evolving
insect-resistant crops. But hot conditions may produce a plague.
Humans Battle Insects In
insecticides or capable of over
coming natural resistances that
have been built up in plants.
“In the case of the sweet-potato
white fly, we’re working very
hard to try to find differences in
appearance, and as yet we have
not been able to find any,” says
Miller. “But there are some major
differences in some of the enzyme
systems and in terms of behavior.”
Such clues are eagerly sought,
as farmers and environmentalists
alike increasingly demand less
reliance on chemical pesticides
such as DDT banned in this
country since 1971 for all but
essential uses to control bugs.
One promising approach to
controlling insects such as the
white fly is to find “good” bugs to
wipe out “bad” ones.
“Most crop-damaging insects
and weeds in the United States
came from somewhere else, but
left their natural enemies behind."
says Richard Soper, who heads the
Agriculture Department’s
research program on natural pest
controls. “We want to turn the
tables on the pests by bringing
their worst adversaries to this
country.”
In 1991, U.S. Agriculture
Department scientists overseas
shipped a record 402,766 pcst
fighting insects and mites into the
United Stales. The bugs are aimed
at helping control more than two
dozen insect pests, as well as
another enemy of agriculture:
weeds.
Bugs are not released wholesale
into the U.S. environment without
careful study to ensure that they
don’t cause more harm than they
were intended to alleviate.
Another line of attack is to help
nature itself as it tries to keep mar
auding insects in check through
plant evolution.
Over centuries of exposure in
Europe, for example, rye has
developed a genetic hostility tow
ard a rye-loving insect known in
this country as the Hessian fly.
The pest is believed to have
been brought into the United
1
States more than 200 years ago in
the straw bedding of Hessian mer
cenaries hired by the British to
fight in the Revolutionary War.
George Washington routed the
Hessians at Trenton, N.J., but their
flies have plagued American
wheat fields ever since.
Wheat varieties that genetically
resist the feeding larvae have been
used to fight the bug. says ento
mologist J.H. Hatchett, who heads
an Agriculture Department
research team in Manhattan, Kan.
But some of those genes are losing
their effectiveness because new
strains of the fly can overcome the
plant’s resistance.
Hatchett’s team is trying to
assist the plant’s natural defenses
by transferring By-resisting genes
from rye to wheat, with the help of
X-rays.
“We feel there’s a possibility
that, in the long run, rye genes
may be more durable than those in
wheat,” Hatchett says.
“My personal view is that we
should be looking toward the*
natural controls rather than chemi
cal controls,” says Douglass Mill
er. “But I do believe we’ll always
be using chemicals of some sort,
because there are going to be
organisms that we don’t know
enough about”
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1. How many hamburgers does the 3. How many stomachs does a co*
AVERAGE American eat each year? have?
a. 114
b. 75
2. How many leather basketballs
can be made from the hide of one
steer?
<• s
Crop Wars
A vedalla ladybug lays eggs atop her lunch: a cottony
cushion scale. The Insect Inside the gummy white sheath
devastated CalNOmla citrus groves In the late 19th century
until farmers Imported the ladybug from Australia. Ancient
Chinese also used “good” bugs—ants to figh “bad" ones
feeding on citrus.
4. In what country was "ham
burger" first made?
a. Russia
b. United States
c. Germany
1. 114. The AVERAGE American eats 114 hamburgers a year
according to U.S. Department of Agriculture research. We each
also cat 80 hotdogs a year. Some people eat more than those
numbers, some eat less. A recent poll by USA Weekend declared
hamburger as America's national food!
2. 12. Twelve leather basketballs can be made from the hide of a
steer. Hidesareused tomakemany leatherproducts weenjoy such
as baseball gloves, shoes, belts, boots, purses and saddles.
3. 1. Cattle are RUMINANT animals. That means they have a
stomach with four compartments. This allows them to eat feeds
like grass and hay, which humans cannot. Cattle are "walking
protein factories" which produce beef for humans from feeds that
we cannot eat.
4. Russia. The people of Tartar (in Russia) liked their beef raw,
chopped fine with salt and pepper. When their ships reached the
German port of Hamburg, Tartar Steak" found its way to Ger
many. Soon a German Chef cooked the Tartar Steak" to make
"Hamburg Steak". Many years later, in America, the chopped meat
cooked Hamburg style became known as the "Hamburg*".
- 2-
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a. 1
b. 4