Group Title: Agricultural research (Washington, D.C.)
Title: Agricultural research
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Title: Agricultural research
Uniform Title: Agricultural research (Washington, D.C.)
Physical Description: v. : ill. ; 25-28 cm.
Language: English
Creator: United States -- Science and Education Administration
United States -- Agricultural Research Administration
United States -- Agricultural Research Service
Publisher: Science and Education Administration, U.S. Dept. of Agriculture :
Science and Education Administration, U.S. Dept. of Agriculture :
Supt. of Docs., U.S. G.P.O., distributor
Place of Publication: Washington D.C
Publication Date: March 2000
Frequency: monthly[1989-]
bimonthly[ former jan./feb.-may/june 1953]
monthly[ former july 1953-198]
Subject: Agriculture -- Periodicals   ( lcsh )
Agriculture -- Research -- Periodicals   ( lcsh )
Agriculture -- Periodicals -- United States   ( lcsh )
Agriculture -- Research -- Periodicals -- United States   ( lcsh )
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Statement of Responsibility: U.S. Department of Agriculture.
Dates or Sequential Designation: Began with vol. 1, no. 1 (Jan. 1953).
Issuing Body: Vols. for Jan./Feb.-Nov. 1953 issued by: Agricultural Research Administration; Dec. 1953-<Sept. 1976> by: Agricultural Research Service; <June 1979>-June 1981 by: the Science and Education Administration; July 1981- by: the Agricultural Research Service.
General Note: Description based on: Vol. 27, no. 7 (Jan. 1979).
General Note: Latest issue consulted: Vol. 46, no. 8 (Aug. 1998).
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Volume ID: VID00033
Source Institution: University of Florida
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Biological Control:

Important Tool for

Managing Invasive


The U.S. Department of Agriculture
has long worked to exclude and manage
invasive species. But globalization of
trade and travel has allowed unprece-
dented spread of foreign plants and
animals. The damage caused by these
invasive pests costs an estimated $122
billion annually in control, loss of re-
sources, and damage to property.
At least 14 federal laws and other ac-
tions have been passed during the last
century to deal with invasive weeds, in-
sects, and other pests. The latest and
most comprehensive, Executive Order
13112, was signed by President Clinton
in February 1999.
Since 1881, biological control-the
deliberate use of one living organism to
control another-has been one of the
tools used to stem the spread of intro-
duced pests. Properly conducted bio-
logical control works because it uses
carefully selected and tested natural
enemies (for example, insects, mites, or
pathogens) of the target pest.
Leafy spurge, for example, is not a
problematic weed in its Eurasian home-
land. But once in the United States, free
of the hundreds of insects and diseases
that naturally limit its growth, it has
spread over millions of acres. By intro-
ducing some of the weed's natural
enemies, scientists help reestablish con-
trols on the weed. The key is to be
selective in choosing these natural
enemies-introducing only those that
are acceptably specific and damage a
susceptible stage or part of the weed.
Concern about introducing any spe-
cies, potentially beneficial or otherwise,
is warranted. That's why for over 120
years, biological control ecologists have
developed and modified a series of tests
that take several years to complete before

a biological control agent is proposed for
First a weed is selected as a target for
biological control because it is perceived
as a significant domestic problem. Then
scientists study the plant in its homeland
to identify the weed's natural enemies.
Once a promising candidate is identi-
fied, many "host-specificity tests" are
conducted to determine whether the
agent will significantly damage the weed
and whether it might also damage crops
or native plants. The goal is to find an
organism that feeds and reproduces en-
tirely or primarily on the target weed, sig-
nificantly damaging it and reducing its
ability to compete with other vegetation.
If an agent passes these tests, the
findings are submitted to the Technical
Advisory Group for Biological Control
Agents of Weeds, an independent group
that advises USDA's Animal and Plant
Health Inspection Service on whether to
approve the release of the agent. If an
agent is approved, it is first imported to
quarantine facilities. There, scientists
confirm that the correct agent was
imported and that no unwanted parasites
or diseases have come along for the ride.
Dozens of researchers both here and
abroad-in ARS and other state and
federal agencies and universities-
participate to identify, test, and import
each biological control agent for each
weed. The first two stories in this issue
of Agricultural Research demonstrate the
cooperation necessary between overseas
and U.S. laboratories to bring biological
control projects to fruition.
Despite the extensive precautions,
biological control, like all integrated pest
management strategies, is not a panacea
and is not risk-free. But that doesn't
mean we should not proceed. The conse-
quences of inaction are far greater than
the risks, as million of acres of rangeland,
cropland, and wildlife habitat are affect-
ed each year.
The very few examples of nontarget
damage from weed biological control
agents receive widespread attention.

However, the most recent catalog of bi-
ological weed control projects notes that
there are only eight examples worldwide
of agent damage to nontarget plants,
"none of which has caused serious eco-
nomic or environmental damage and the
majority of which were anticipated by
routine testing before release."
This catalog contains data on more
than 350 biological control agents re-
leased against 133 weeds in more than
70 countries in the last 120 years.
Further, the vast majority of this
nontarget damage is short term and in-
significant. For example, an agent may
nibble on a nontarget plant but can't
complete its life cycle on the plant and
dies off without reproducing.
To further improve the practice of
weed biological control projects, ARS
recently revised its policy. Now, each
project is considered to last at least 20
years, even though individual compo-
nents may take only 3 to 5.
Biologically based integrated weed
management (biological control with
cultural control/revegetation) is the basis
of our programs. Chemical and mechan-
ical strategies are still vital in many
instances and may be used in combi-
nation with biological control.
ARS is also committed to long-term
monitoring of the effects of agents on
target weeds and on potential nontarget
species closely related to target weeds.
Finally, ARS continues to lead in fos-
tering partnerships with other federal and
state agencies, universities, overseas
groups, private organizations, and land-
owners. The invasive species problem is
too vast for anyone to tackle alone.
Biological control takes many years
to succeed. But it is often the best, safest,
and most cost-effective approach to long-
term management of widespread, inva-
sive weeds. Sometimes it is the only
practical approach.

Ernest S. Delfosse
ARS National Program Leader for
Weed Sciences

Agricultural Research/March 2000

March 2000
Vol. 48, No. 3
ISSN 0002-161X

.4A-rrtf iural Re 'tarc i, published monthly by
the Agricuhlurai Re-earch Sern ie. Li S Depart-
meni ot Agriculture I LiSD.A The Secretary of
Agriculure hja determined thdai [hi periodical is
necessary in the transaction of public business
required by law.
Dan Glickman, Secretary
U.S. Department of Agriculture
I. Miley Gonzalez, Under Secretary
Research. Educjiion. and Economics
Floid P Horn. Adminiitrarior
agriculturall Reearch Ser\ Ie
Sand; .Niller Hai, Director
inforniaonii Stafr
Editor: Robert Sowers (301) 504-1651
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This magazine may report research involving pes-
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Reference to any commercial product or service
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Agricultural Research

Foreign Agents Imported for Weed Control 4

Watch Out Water-hyacinth! 10

Feeling Weak? Try the Tortillas! 13

Overweight? Losing Excess Weight Is More

Important Than Trimming Dietary Fat 14

Jellyfish Gene Lights Up E. coli 15

Whence Come Hog Manure Odors? 16

Medfly Leftovers = Gourmet Feed 18

A Unique Potato Virus Collection 19

Curbing Wind-Blown Dust 19

Zapping Airborne Salmonella and Dust 20

Screening Mites From Honey Bees 22

Science Update 23

Cover: Although pretty at certain times of the year, saltcedar is an invasive exotic
weed that is harming both agriculture and the environment. Here, it is overtaking
native vegetation along the Gila River in Arizona. Photo by Jack Dykinga. (K8770-1)

In the next issue!

( REVEGETATING THE WEST ARS scientists have developed three
hardy native species to help cover rangelands denuded by fire and mining.

A new map of chicken genes is being developed in tandem with the human
genome map. The results show surprising similarities that could improve
disease resistance in chickens and people.

typically stimulate crop growth and yields, but what happens when ozone
and other stresses enter the picture?

Agricultural Research/March 2000

i. /

6 ; .


1 II

and greenhouses that hold beneficial
insects from foreign lands. These in-
sects, scientists and landowners hope,
may help control some of the United
States' worst weed invaders-like leafy
spurge, saltcedar, and melaleuca.
"Invasive species, including weeds,
cost U.S. consumers and producers
billions of dollars each year," says
Ernest S. Delfosse, the Agricultural
Research Service's national program
leader for weed sciences in Beltsville,
Maryland. "Natural enemies from the
weeds' homelands may be our most ef-
fective and economical tools for long-
term control."
When beneficial insects arrive from
overseas, they are carefully sorted,
screened for parasites, and reared in
quarantine facilities like the one just
described, which is located at ARS'
Western Regional Research Center in
Albany, California.
Though the specifications may differ,
about two dozen U.S. quarantine fa-
cilities serve as strictly regulated gate-
ways for importing biological control
agents. Researchers at some locations
focus on beneficial insects like wasps
to control insect pests such as alfalfa
weevils or gypsy moths. Those at other
locations look at diseases and other mi-
croscopic agents for both weed and in-
sect control.
This story highlights ARS research
on using beneficial insects for biological
control of weeds. ARS operates lab-
oratories with quarantine facilities in
Albany; Stoneville, Mississippi; and
Temple, Texas. New quarantine oper-
ations will open in Fort Lauderdale,
Florida, and Sidney, Montana, within the
next few years.
ARS also collaborates with univer-
sities and other state and federal agen-
cies that run additional quarantines,

Technician Eve Lednicky examines
beneficial insects being evaluated within the
containment portion of the ARS quarantine
facility in Albany, California.

including a long-term program at Gaines-
ville, Florida. Each uses a variety of traps,
doors, entryways, and sanitizing proce-
dures to keep the insects inside until they
are intentionally released on approved
weed targets.
Biological control aims to restore
some of a weed's natural complement of
enemies, making it less damaging here.
This approach has been used successful-
ly and safely for many years. Since 1945,
more than 110 insect species have been
released in the continental United States


Aphthonaflava flea beetle feeding on
leafy spurge.

and Hawaii against some 57 weeds. Some
of the worst pests no longer cause signif-
icant damage.
"Of course, we have to ensure that we
protect our natural resources at the same
time," Delfosse says. "The quarantine fa-
cilities are just one of the steps we take
to keep biological control safe."
In tandem with the domestic labora-
tories, ARS operates or collaborates in the
operation of several overseas laboratories

for hands-on discovery and collection of
the weeds' natural enemies (see story on
ARS' foreign biological control labora-
tories, page 7). These labs are in
Montpellier, France; Hurlingham, Argen-
tina; Beijing, China; and Indooroopilly,
Often working with local landowners
and biologists, ARS researchers look for
the insects that will likely do the most
damage to the weed and the least dam-
age to anything else. Scientists at the for-
eign labs study the basic biology of the
insect agents. They verify that the insects
significantly damage the weed and be-
gin testing to make sure the insects don't
eat or reproduce on U.S. native or crop
Together with hundreds of coopera-
tors here and overseas, ARS quarantine
and foreign research laboratories serve
as an invaluable pipeline for identifying,
testing, importing, and releasing bio-
logical control agents against some of our
most troublesome weeds. USDA's Ani-
mal and Plant Health Inspection Service
(APHIS) plays a key role in regulating
the importation of all beneficial organ-
isms, as well as overseeing quarantine
facilities. Several examples highlight this
unique research conduit.

A Key Strategy for TEAM Leafy
First identified in the United States in
1827, leafy spurge (Euphorbia esula)
now infests at least 5 million acres in 35
states and Canadian provinces. The weed
degrades grazing lands for livestock and
wildlife and reduces land values.
ARS began research on biological
control of leafy spurge in the 1970s at
laboratories in California, Montana, and
Italy. Since then, ARS, APHIS, and for-
eign cooperators have discovered, im-
ported, and released 12 natural enemies.
The stars so far have been a group of
four related flea beetles from Eurasia that
belong to the genus Aphthona. The bee-
tles have rapidly expanded from some
areas. At one site in North Dakota, where

Agricultural Research/March 2000

77 beetles were released, about 2
million were harvested in 1999 for
distribution to other spurge-infested
The young beetles burrow into the
weed's roots. Adults feed on the leaves.
In addition to harming the plant directly,
this feeding allows invasion by disease-
causing fungi or bacteria and impairs
its reproduction.
"There is no question that biological
control will be a key to long-term
control of leafy spurge," says Neal R.
Spencer, an entomologist who leads
research at ARS' Northern Plains
Agricultural Research Station in Sidney,
To demonstrate biological control
and other integrated pest management
(IPM) techniques for leafy spurge, ARS
formed The Ecological, Areawide Man-
agement (TEAM) Leafy Spurge project
in 1997. ARS and APHIS coordinate the
project, with participation by dozens of
other federal, state, and local organiza-
tions and ranchers.
TEAM Leafy Spurge is the third in
a series of ARS-funded, 5-year IPM
projects but the first to target a weed.
Researchers examine biological, cultur-
al, and chemical methods individually
and in combination to manage the weed.
The goal is to find the best tools, from
an environmental and economical
standpoint, so ranchers and land man-
agers can reclaim rangeland lost to the
weed and slow its further spread.
"So far, the project has been a big
success," says Spencer. Last summer,
TEAM Leafy Spurge distributed for re-
lease more than 22 million flea beetles
to 206 ranchers and land managers from
50 counties in 7 states.
The Aphthona beetles will soon be
joined by a gall midge, Spurgia capiti-
gena. Unlike flea beetles, the midge pre-
fers moist, shady areas. That will give
TEAM Leafy Spurge another tool to
slow spurge growth in areas where
beetles, grazing sheep and goats, or
pesticides aren't effective or practical.


iviealyougs ( raounna mannipara) are In Kazakhstan and western China, the
being considered as a biological control midge Psectrosema noxium attacks
agent for saltcedar. These egg sacs are on saltcedar and forms galls on it, killing the
saltcedar in quarantine at Temple, Texas. terminal stems.

Agricultural Research/March 2000

Rouhollah Sobhian, an ARS entomol-
ogist, has located a good natural source
of the midge in southern France. Scien-
tists in Europe and Montana have studied
the midge, and Spencer has already ob-
tained a release permit from APHIS.

Chinese Beetles for Saltcedar Control
Landowners in the western United
States brought in bushy, deciduous salt-
cedar (Tamarix spp.) trees for erosion
control in 1837. Since then, saltcedar has
crowded out native trees like willows and
cottonwoods along parts of nearly every
western river.
In 1987, ARS launched a project to
use biological control against the weed.
ARS researchers, along with cooperators
in China, France, Israel, Kazakhstan, and
Turkmenistan, began plant studies and
identified potential natural enemies. A
leaf beetle, Diorhabda elongata, and a
mealybug, Trabutina mannipara, were

In 1991' 4fW,;
European BR
maintaining si,
In 1999, new
1,600-square-footoe tqu -
facility for plant path
eeds present in Fjanw,, ,.
sects from several cont
env ironment..
The lab has introduced ai
agents that help control at leas t.l
Major weed targets now-. i l
starthistle, Russian knapweed,aip
"This unique resource has paid farief
to find and test natural enemies of 'iedS,'"
s.cientit \\ho runs EBCL. "With ontnur eqaio
an e en greater _ervice."
ARS also supports biological control laborato
LUSDA's Asian Parasite Laboratory, originally -Iear
to South Korea, performed biological control studies
gap bet een 1941 and 1975). Researchers at thi:S,
test agents for control of leafy spurge and saltcedai.-t
To continue research in Asia. ARS and the Clines
Sciences, established the Sino-American Collaboratirio
story in Beijing. China. in 1988. Today the lab works orin.
least\ spurge. se eral aquatic % eeds, and some insect ptests;
In 1989. ARS opened the Australian Biological Control Lab
in cooperation % ith the Commonweath Scientific andti
Organization ICSIRO). The mission of this lab is to evaluate
agent, for \\eed% of Australian and Southeast Asian origin, Rese-
disco ered biological controls for many of the invasive Vietl!tn
in the southern and western United States, such as melaleuca. lO
tern. and hidrilla Onsite CSIRO quarantine facilities allow. ARS i
rejr insects for preliminary\ testing. -::"V,'
The ARS South Amencan Biological Control Laboratory near B-li
Argenuna. opened in 1902 to tackle alligatorweed and water-hyacini k
there lihas since expanded to include %%aterleiruce. tropical soda apple,
tropical \\eeds. rangeland \\eeds. and insect pests such as fire ants.

Agricultural Research/March 2000

shipped to ARS quarantine labs in
Albany and Temple for further study.
Last summer, the beetle was approved
as the first biological control agent for
saltcedar. The adults and young feed on
saltcedar leaves, repeatedly defoliating
the tree and depriving it of nutrients.
Normally, control agents are approved
for direct release into target areas. But
this time, researchers faced a unique
"Saltcedar replaced native willows
that an endangered bird-the southwest-
ern willow flycatcher (Empidonax traillii
extimus)-relied on for nesting," says
ARS entomologist Jack DeLoach. "The
bird has since adapted to nesting in salt-
cedar, so we have to ensure that the bee-
tles won't remove the weed faster than
we can reestablish native plants for the
birds." DeLoach is in the ARS Grassland
Protection Research Unit at Temple.
To protect the bird while controlling
the weed, the scientists implemented an
extra step, in concurrence with APHIS
and the U.S. Fish and Wildlife Service:
a 3-year experimental phase that begins


The leaf beetle Diorhabda elongata is the
first approved biological control agent for
saltcedar in the United States.

with the beetles in cages. This will al-
low scientists to monitor the rate at which
the beetles damage the saltcedar before
the insects are relocated to other critical
A consortium of experts from more
than two dozen federal, state, and local
agencies; uni-
versities; and GARY BUCKINGHAM (K7658-2)
meets periodi-
cally to devel-
op monitoring
protocols, re-
view progress,
and address
Despite the
species con- Oxyops vitiosa, a leaf
cerns, scien- weevil, is thriving on
tists are confi- invasive melaleuca in
det tat te southern Florida.
dent that the
biological con-
trol approach
is the right choice for managing saltcedar.
"Saltcedar is an Old World plant with
no close native relatives here," says ARS
entomologist Raymond I. Carruthers.
"More than 200 natural enemies of
saltcedar have been found in China and
the former Soviet Union. Insects like the
Diorhabda beetle feed exclusively on
saltcedar, making them ideal for biol-
ogical control." Carruthers leads the
Exotic and Invasive Weed Research Unit
at Albany.
The next likely candidate will be a
weevil from France, China, and Kazakh-
stan, belonging to the genus Coniatus.
Like the Diorhabda beetle, the larvae eat
the foliage. But young Coniatus pupate
on the tree before they emerge as adults,
while Diorhabda fall to the ground to
pupate and can be drowned in wet areas.
Both the leafy spurge and saltcedar
projects are using high-tech tools such
as aerial photography, remote sensing,
and geographic information systems
(GIS), to map the weeds over vast areas.

ARS ecologist Gerry Anderson in Sidney
and ARS rangeland scientist Jim Everitt
at Weslaco, Texas, coordinated some of
the mapping.
"It is often difficult to determine the
extent and distribution of weed popu-
lations on rangelands because of the
expanse and inaccessibility of these
areas," Anderson says. "These technol-
ogies will provide a comprehensive way
to measure the rate at which the weeds
spread and the long-term effectiveness
of biological control over wide regions."

Showing Promise for Water Weeds
and Melaleuca, Too
Foreign aquatic plants have also in-
vaded and become weeds. ARS began
its search for biological control agents
of water weeds by establishing labora-
tories in Florida in 1959 and Argentina
in 1962. Water-hyacinth was one of the
original targets and remains a high pri-
ority today.
By 1992, water-hyacinth had invaded
hundreds of lakes and streams through-
out the South and parts of the West and
Hawaii. The weed impedes water's nat-
ural flow and can destroy native com-
munities of aquatic plants and animals.
Biological control has already greatly
reduced water-hyacinth in Florida,
Louisiana, and Texas, but more agents
are needed.
ARS researchers here and abroad are
discovering and testing what they hope
will be a new South American team of
natural enemies (see story on page 10 in
this issue).
Also under way is a promising project
to curb melaleuca, Melaleuca quinquen-
ervia. A tiny, grey-brown weevil called
Oxyops vitiosa is now thriving in at least
50 sites in south Florida, thanks to more
than a decade of work by ARS scientists
there and in Australia. Researchers hope
the leaf-eating Oxyops will stop the
spread of melaleuca, a fast-growing tree
that crowds out native vegetation and is
threatening to take over Florida's

Agricultural Research/March 2000


The Scotch thistle weevil from Spain is
being evaluated in the Albany quarantine
facility to determine if it is safe for release
in the United States.

INear tort Lauaerdale, lFloria, suo-oot-mgn melaleuca trees threaten to destroy the delicate
ecosystem of the Everglades.

Both melaleuca and 0. vitiosa, the
melaleuca leaf weevil, are native to
Australia, but neither is a pest there. ARS
scientists turned the 1/4-inch-long weevil
loose at 13 melaleuca-infested sites in
Florida in 1997, after exhaustive green-
house testing and investigations by
colleagues in Australia showed the insect
would not attack other plants. (See
"Aussie Weevil Opens Attack on Ram-
pant Melaleuca," Agricultural Research,
December 1997, pp. 4-7.)
"Although it's too early to call the
weevils a success," says ARS entomolo-
gist Ted D. Center, "all indications are
that they are doing great." Center leads
the ARS Aquatic Weed Control Research
Unit at Fort Lauderdale.
"One site where we originally re-
leased 3,300 weevils," he says, "now has

about 80,000. We collected about 20,000
weevils there and relocated them to 30
new sites. That means we've now placed
weevils throughout melaleuca's entire
Florida range.
"In general," Center says, "the wee-
vils have done well at sites that are dry
or only seasonally wet. But at permanent-
ly inundated areas, they may drown when
trying to find soil in which to pupate."
But other biological control agents
that might thrive at those soggy sites
could be waiting in the wings. After all,
the melaleuca-munching weevil was only
one of more than 450 plant-eating crit-
ters that scientists at the ARS Australian
Biological Control Laboratory in In-
dooroopilly, near Brisbane, found feed-
ing on melaleuca. Today, the team is fo-
cusing its melaleuca research on six of

the most promising agents-some of
which have already been shipped to
Gainesville, Florida, for in-quarantine
scrutiny by a team of ARS scientists led
by entomologist Gary Buckingham.
"Our ongoing field research in
Australia ensures that ARS scientists in
Florida have the widest possible array of
biological control agents to work with,"
says entomologist John A. Goolsby,
director of the ARS Australian Biological
Control Laboratory. "This dual-continent
approach," he says, "invites success."-
By Kathryn Barry Stelljes and Marcia
Wood, ARS.
This research is part of Crop Protec-
tion and Quarantine, an ARS National
Program (#304) described on the World
Wide Web at http://www.nps.ars.usda.
gov/programs/cppvs. htm.
Scientists mentioned in this story can
be contacted through Kathryn Barry
Stelljes, USDA-ARS Information Staff,
800 Buchanon St., Albany, CA 94710;
phone (510) 559-6069, fax (510) 559-
5882, e-mail *

Agricultural Research/March 2000

AoUve, grey-Wllmle liyillpl UJ oIUUS U pIllL
hoppers feed on heavily damaged water-
hyacinth. The sap-sucking insects not only
damage and weaken the weed, they
introduce plant pathogens.
HUGO CORDO (K8800-2)

.."1. 1rn, nn11

ou can't get to Iquitos, Peru,
without a boat or a plane. But
this jungle-locked city of
350,000 in the rainforests of the
upper Amazon River is the
business and tourism hub of Peru's
eastern lowlands.
In the late 19th century, rubber made
Iquitos a major trade center. Today, tour-
ists can visit old rubber-baron mansions
like Casa de Hierro (Iron House), de-
signed by Gustave Eiffel of Paris.
Iquitos has a different appeal for
Agricultural Research Service ento-
mologist Hugo Cordo. "This region may
be the world's richest source of natural
enemies of water-hyacinth," he says.
Cordo leads the ARS South American
Biological Control Laboratory in Buenos
Aires, Argentina.
Water-hyacinth, Eichhornia cras-
sipes, is a free-floating perennial herb.
The plants grow about 3 feet tall as they
float on the water's surface, with stems
intertwining to form dense mats.
In the Amazon the plant is held in
check by natural enemies such as insects
and microbes. These organisms stress the
plants, controlling the mat's expansion.
But water-hyacinth has escaped to friend-
lier waters, especially since the 1800s.
Often, visitors, drawn by its lush leaves
and blue-to-lavender flowers, have tak-
en it home as an ornamental.

A Floating Nightmare
Out of its enemies' reach, water-
hyacinth has become the worst floating
aquatic weed in many tropical and

subtropical parts of the Americas, Asia,
Australia, and Africa. In Africa it infests
every major river and nearly every major
freshwater lake. In the United States, it
flourishes in hundreds of bodies of water
in Hawaii and California and throughout
the South from Texas to the Carolinas.
Today, increased cooperation by gov-
ernments and scientists around the world
is turning up the heat on water-hyacinth.
The more unique natural enemies that
scientists can find and evaluate, the more
likely they can deploy new biological
control cadres suited to the weed's vari-
ous growth stages and to different cli-
mates and other conditions.
At worst, this plant may be a killer. In
the Sepik area of Papua New Guinea, it
has been blamed for making people
starve. According to Australian scientists
K.L.S. Harley, M.H. Julien, and A.D.
Wright, people "could not access subsis-
tence gardens, hunting areas, catch fish,
or travel to market to sell and buy pro-
duce" because of dense water-hyacinth
More typically, water-hyacinth dam-
ages water quality by blocking sunlight
and oxygen and slowing the water's flow.
Capable of doubling within a couple of
weeks, it can grow faster than any other
plant. By choking out other vegetation,
it makes an area unusable by plants and
animals that live in or depend on the
water. Fish spawning areas may vanish.
In the Florida Everglades of the
United States, the snail kite (Rostrhamus
sociabilis) is endangered partly because
this bird can't find apple snails-its

Agricultural Research/March 2000


The Megamelus plant
hopper (about 3 nun
long) may provide
badly needed help in
controlling water-

favorite food-where the weed has
smothered the snail's favored food
plants. In some parts of the world, the
mats form habitat for disease-carrying
mosquitoes as well as snail species that
are intermediate hosts for schisto-
somiasis, among the world's worst
parasitic diseases.
Uncontrolled, water-hyacinth robs
water from potential drinking and irriga-
tion supplies. The mats can block boat
travel. Chunks of mat can break free to
clog downstream pump stations supply-
ing water for drinking, irrigation, and
Chemicals and mechanical removal,
the primary weapons against the weed,
are costly and often ineffective.

Searching for Its Nemesis
Scientists believe that the best bet for
a long-term solution is to introduce one
or more natural enemies as biological
Two decades ago, Cordo and ARS en-
tomologist Jack DeLoach in Temple,
Texas, led an effective biological con-
trol program at Argentina's Dique los
Sauces reservoir. In the 1970s, ARS re-
searchers Ted Center and Neal Spencer
were the first to release in the United
States two South American weevils
(Neochetina bruchi and N. eichhorniae)
and the water-hyacinth borer (Sameodes
These and other organisms are being
deployed in more than 20 other countries,
including Australia, Cuba, Egypt, Hon-
duras, Indonesia, Malaysia, Mexico,

Panama, South Africa, Thailand, Viet-
nam, and Zimbabwe. There have been
many successes, but results have been
variable and the weed continues to cause
"For years," says Cordo, "we thought
most of the best potential biological con-
trol agents were already found."
"But until now," Center notes, "no one
had really looked for them in the upper
Amazon. That is probably the area where
water-hyacinth originated-where you
might expect to find the greatest diversity
of natural enemies." Center leads ARS'
Aquatic Plant Control Research Unit in
Fort Lauderdale, Florida.
This scientific optimism brought Cor-
do, Center, and three other scientists to
Iquitos in late April 1999. The others
were entomologist Martin Hill with
South Africa's Plant Protection Research
Institute and plant pathologists Harry
Evans and Djami Djeddour of CABI Bio-
science in England.
They searched for natural enemies
along 180 kilometers of the upper Ama-
zon and the two rivers that converge to
form it-the Ucayali and Marafion.

Into the Thick of It
On April 27, guide Andrds Guerra
motored the group down the Amazon in
a small aluminum boat. "We were look-
ing for water-hyacinth growing in
cochas," Cordo says. Cochas-bayous
and depressions away from the river
channel-are typically concealed behind
the wall of rainforest lining a river

Agricultural Research/March 2000

Thrypticus fly
(about 2 mm

Eventually the group stopped at an
area Guerra said was near cochas. With
a machete, he hacked low branches and
vines to clear the boat's path through the
flooded forest. "For a half hour," says
Cordo, "we thought we were heading to
nothing. But suddenly, the cochas were
there. We steered into the water-hyacinth
mat and began using our hands and a
sweep net to collect insect and plant sam-
In all, the scientists collected hun-
dreds of natural enemies and plant sam-
ples at 30 sites in 7 days. From the first
day, the excitement was about a tiny in-
sect, a water-hyacinth fly that none of
the scientists had seen before.
In Buenos Aires, Cordo's team had
already been testing several promising
insects, including three species of
Thrypticus flies collected since 1996 in
Argentina. Now, it appeared they had
found a new Thrypticus.
The female Thrypticus deposits an
egg in a water-hyacinth petiole-the
stalk that attaches the leaf to the stem.
The young larva feeds on the inner tis-
sue. Within the petiole it digs ultranar-
row tubes called mines. The mines have
one or more tiny spurs that exit the pet-
iole's outer skin. "Water doesn't enter
these tiny orifices," Cordo says, "and we
don't know why the fly makes them. But
they may serve as doorways for patho-
gens to enter and further weaken the
Each Thrypticus species has a unique
mining pattern. One is shaped like the
letter "U"; another is C-shaped. But at
site 1-and later, other sites-the scien-
tists found ringlike mines with several
orifices. "We believe the Thrypticus that
made these is a new species," Cordo
says. "And it appears to be a specialist
in attacking very young petioles."

A Bountiful Harvest
During the trip, the scientists also
found as many as three new species of
Taosa plant hoppers. Only one had been
reported in the scientific literature. Taosa

and Megamelus plant hoppers are sap-
sucking insects that, like their whitefly
cousins, can transmit plant pathogens.
Cordo says the Taosa especially "are
impressive because of their impact in
combination with a pathogen we have
not yet identified. Infested plants were
short, weak, and full of spots made by
the pathogen."
The insect identifications are prelim-
inary, but 11 species new to science have
been collected so far by the ARS research
team on water-hyacinth and its relatives
in Iquitos and northern Argentina since
TED CENTER (K8801-2)

1996: six Thrypticus, three Taosa, and
two Megamelus species.
The ARS scientists at Buenos Aires
have been conducting numerous studies
of the insects' biology and behavior.
They will screen colonies of insects they
collect to find out which might do the
most damage to water-hyacinth.
They are also making sure water-
hyacinth is the only important plant
attacked. "Along with crops, this means
testing ornamentals and plants in natural
settings," Cordo says. "We've already
determined that the new Thrypticus and
one of the Megamelus do not attack
plants in other families. And they will
not attack the one U.S. plant in the water-
hyacinth family that we don't want to

hurt." That plant, pickerel weed, is used
by many small aquatic animals.
Cordo, Center, and Hill, the South
African scientist, are collaborating to
determine how best to rear Megamelus
and Thrypticus for lab and outdoor tests.
"With luck," Cordo says, "Thrypticus
might be ready to import in 2 or 3 years,
for testing first in the Fort Lauderdale lab.
With Megamelus, that time may come
sooner, since we already know how to
rear small lab colonies of it."-By Jim
De Quattro, ARS.
This research is part of Crop Protec-

tion and Quarantine, an ARS National
Program (#304) described on the World
Wide Web at
/programs/cppvs. htm.
Hugo Cordo is at the USDA-ARS
South American Biological Control Lab-
oratory, Hurlingham, Argentina; tele-
phone and fax 54-11-4662-0999, e-mail His mailing
address is Agricultural Counselor ARS
Lab, U.S. Embassy Buenos Aires, Unit
4325, APO AA 34034-0001.
Ted D. Center is at the USDA-ARS
Aquatic Plant Control Research Unit,
3205 College Ave., Fort Lauderdale, FL
33314; phone (954) 475-0541, ext. 103,
fax 954-476-9169, e-mail tcenter@ars. *

Agricultural Research/March 2000


Geneliciis Victor Rahbo examines a plant from a new line of corn he developed. ThI
from the ner corn is designed to he louer in phytic acid, a compound suspected toi1
nulrieni absorption during human digestion.

C an corn combat anemia? It's a possibility.
Tortillas and other foods made from the flour of a
unique corn may help combat iron-deficiency anemia.
That could be a boon in developing countries where
corn-based foods are a part of nearly every meal. In
fact, products made from this corn could become use-
ful around the world, since iron deficiency is fairly common
in developed nations as well.
The novel corn, according to Agricultural Research Service
geneticist Victor A. Raboy at Aberdeen, Idaho, may help the
body to better absorb and use iron-an essential nutrient.
The plants that Raboy developed yield corn that's low in a
naturally occurring compound called phytic acid, or phytate.
Phytic acid is thought to reduce the body's ability to use cer-
tain nutrients, like iron.
The Raboy corn lines have up to 95 percent less phytic acid
than most common varieties.
Researchers from the Institute of Nutrition of Central Amer-
ica and Panama and from the University of California's Ber-
keley and Davis campuses coordinated the corn-flour experi-
ment with Raboy. Fourteen healthy men, age 19 to 35,
volunteered for the investigation, which was conducted at
Blood tests indicated that iron absorption by the volunteers
was about 50 percent greater if they ate tortillas made from
flour of low-phytic-acid corn than if they ate tortillas prepared
with normal corn flour having about two-thirds more phytic
The Rockefeller Foundation, U.S. Agency for International
Development, and Pioneer Hi-Bred International, Inc.-one

of three companies licensed by ARS to produce the corn-
helped fund the research.
Raboy says the study is the first to test the potential nutri-
tional benefits of the low-phytic-acid corn in humans. Next, a
team led by University of Colorado researchers will probe the
effects of the corn on zinc, iron, and calcium absorption in a
new study in Guatemala.
The unusual corn, patented in 1997, has already received
national attention because of its ability to reduce phosphorus
pollution in ponds, lakes, streams, and rivers. Phytic acid is a
form of phosphorus, an essential mineral. Raboy's low-phytic-
acid corn is correspondingly high in inorganic phosphorus-
the form that one-stomached animals like pigs, chickens, or
farm-raised fish can readily absorb and use.
These animals can't absorb most of the organic phosphorus
in conventional corn, so too much of it can end up in their
manure. Phosphorus leached from manure may make its way
into rivers and streams, leading to algal blooms and fish kills.
Ongoing experiments in the United States and abroad will
reveal more about the ways that the special corn-and other
grains with the low-phytic-acid trait-should benefit people,
animals, and the environment.-By Marcia Wood, ARS.
This research is part of Plant, Microbial, and Insect Genet-
ic Resources, Genomics, and Genetic Improvement, an ARS
National Program (#301) described on the World Wide Web at
Victor A. Raboy is with the USDA-ARS Small Grains and
Potato Germplasm Research Unit, 1691 S., 2700 W., P.O. Box
307, Aberdeen, ID 83210; phone (208) 397-4162, ext. 151,fax
(208) 397-4165, e-mail *

Agricultural Research/March 2000



Excess Weight Is More
Important Than Trimming
Dietary Fat

R educe the fat in your diet, particularly
saturated fat. That's the standard pre-
scription for lowering blood cholesterol.
But it doesn't work as well for everyone.
For example, people who are obese-
20 percent over their ideal weight-need to trim
extra pounds in order to get the full benefit from
trimming dietary fat.
What about people who are overweight but not
obese? Would they be better advised to focus
on dropping extra pounds-or dropping
some dietary fat?
Researchers at the University of
Cordoba Medical School in Spain
enlisted 41 young men to answer
the question, with help from
their U.S. colleague, Jose M.
Ordovas. He's at USDA's
Human Nutrition Research
Center on Aging at Tufts
University in Boston.
Ordovas is a pioneer in assembling
a profile of genes involved in heart disease risk.
(See "Attacking Heart Disease at Its Genetic
Base," Agricultural Research, July 1999, pp.
20-21.) "We're trying to customize the
prescription for reducing risk," he says. "It's
now a matter of trial and error."
He says genes involved in bodyweight ap-
pear to hold sway over genes that control how
blood lipids respond to dietary changes. Los-
ing weight switches off some weight genes, can-
celing their effect on the genes that affect blood
lipid levels. In fact, some of the genes involved
in this interaction may be the same.
The researchers tested three diets on the men.
Half were overweight, with a body mass index
(BMI) between 25 and 30 kilograms per meter
squared (kg/m2). That's equivalent to a 6-foot
man weighing 185-215 pounds, or a 5-foot, 8-
inch man weighing 165-195 lbs.
For 4 weeks, the men ate a high-fat diet: 38
percent fat, 20 percent of which was saturated

fat. Then they switched to the low-fat diet recommend-
ed by the National Cholesterol Education Program
(NCEP)-28 percent fat, 10 percent saturated fat. Last-
ly, they ate another high-fat (38-percent) diet. But in-
stead of being heavy in saturated fat, it was high in
monounsaturated fats (22 percent)-the predominant
fats in olive and canola oils. These fats are proving
beneficial for the cardiovascular system.
The overweight men began with higher
total cholesterol and triglycerides than the
slim group and less "good" HDL cholester-
ol. Ordovas says blood lipids are correlated
with body weight and BMI.
Both heart-healthy diets were less
effective at improving the cholesterol pro-
file in the overweight men. On the NCEP
diet, their total cholesterol drop was less than
half that of the lean men-7 percent versus
16 percent. Likewise, their artery-damaging
LDL cholesterol dropped 9 percent, compared to 21 percent
for the lean group.
The researchers concluded it's more important for over-
weight men to lose weight than to change the fat content of
their diets.
The overweight men did have a bigger drop in tri-
glycerides when eating the diet high in mono-
unsaturated fats. This suggests that portly people
should substitute olive or canola oil for saturated
"High triglycerides are associated with reduced
glucose tolerance"-the earliest stage of diabetes,
says Ordovas. "And evidence is mounting that they
are an independent risk factor for heart disease."-
By Judy McBride, ARS.
This research is part of Human Nutrition, anARS
National Program (#107) described on the World
Wide Web at
S grams/appvs.htm.
Jose M. Ordovas is at the USDA-ARS Jean May-
er Human Nutrition Research Center on Aging at
Tufts University, 711 Washington St., Boston, MA
02111; phone (617) 556-3102,fax (617) 556-3103,
e-mail +

Agricultural ResearchlMarch 2000

Jellyfish Gene Lights Up E. coli

A jellyfish gene is helping re-
searchers discover the secrets
of how a food-poisoning bac-
terium spreads. Microbiologist
Marian R. Wachtel with the
Agricultural Research Service in Cali-
fornia has inserted the gene into
laboratory strains of the foodborne bac-
terium Escherichia coli 0157:H7.
In nature, the gene cues a jellyfish to
make a bright-green fluorescent protein.
In Wachtel's laboratory, the fluorescence
acts as a readily detectable marker that
makes it easier for her to spy on E. coli
microbes as they attempt to colonize the
leaves of fresh lettuce.
If consumed, E. coli 0157:H7 can
cause bloody diarrhea and in some
instances can lead to acute kidney failure,
requiring patients to undergo dialysis.
The microbe is unusual in that most other
bacteria in the same family are harmless
to humans.
Wachtel says her fluorescence-based
assay enables researchers to quickly de-
tect the presence and quantity of the ge-
netically engineered bacterium in lettuce.
This powerful new technique should help
her and other food safety scientists test
the effectiveness of new tactics designed
to keep the pathogen out of food.
Viewed with ultraviolet light in the
laboratory, the microbe fluoresces a
bright green. "We can detect the fluo-
rescent, genetically engineered microbe
not only as it attaches to the surface of

lettuce leaves," reports Wachtel, "but
also if it moves deep within lettuce
tissue." She is with the Food Safety and
Health Research Unit at ARS' Western
Regional Research Center at Albany,
Outbreaks of E. coli 0157:H7 linked
to contaminated lettuce are infrequent,
occurring only about once a year in the
past 9 years. But ARS scientists like
Wachtel want to help growers, proces-
sors, and consumers ensure that the pop-
ular leafy vegetable remains safe to eat.
Wachtel says that eating fresh lettuce,
properly washed, "should pose no sig-
nificant health hazard."
The idea of moving the fluorescence
gene, borrowed from Aequorea victoria
jellyfish, into other organisms isn't new.
But Wachtel is among the first to make a

detailed study of plant tissue with fluo-
rescent E. coli 0157:H7 added.
So far, she's used the assay in labo-
ratory experiments with romaine, green
leaf, and iceberg lettuces that she has
artificially infected with the genetical-
ly engineered E. coli.-By Marcia
Wood, ARS.
This research is part of Food Safety,
an ARS National Program (#108) de-
scribed on the World Wide Web at http:/
Marian R. Wachtel is with the USDA-
ARS Food Safety and Health Research
Unit, Western Regional Research Cen-
ter, 800 Buchanan St., Albany, CA
94710; phone (510) 559-5957, fax (510)
559-5948, e-mail wachtel@pw.usda.
gov. *

A confocal scanning laser micrograph of fluorescent
green E. coli gaining access to the xylem of cut leaf
lettuce. (Magnification about 1,000x.)

Agricultural Research/March 2000

a a a *gg

In a swine facility near Peoria, Illinois, microbiologist Terry Whitehead collects fresh manure
samples for use in tests to identify bacteria that may be involved in odor production.


Researching the question "What
makes manure stink?" is no ivo-
ry-tower pursuit for ARS mi-
crobiologist Michael A. Cotta
and his colleagues.
In their view, finding which microbes
are responsible is a fundamental step
toward helping the livestock industry
improve production efficiency and live
in harmony with their rural and urban
The scientists at the National Center
for Agricultural Utilization Research in
Peoria, Illinois, are focusing on bacteria
that thrive in the lower digestive tract of
swine and in waste handling facilities.
These bacteria produce myriad odors
from feed that's not fully digested. Once
the researchers know which culprits

Once odor-producing
chemicals are identi-
fied, feed formulations
can be changed and
new waste handling
systems developed to
reduce odors.

produce the worst odors and how,
animal nutritionists and agricultural
engineers can work on the problem with
new types of feed and new waste
handling systems.
In swine waste, all too prevalent mal-
odorous compounds include ammonia,
organic acids, alcohols, and-the most
offensive of all-sulfides. Some of the
compounds can have bad health effects
on animals and humans. For example,
chronic exposure to air with high am-
monia concentrations can harm the
respiratory system.
Microorganisms in waste storage pits
and treatment lagoons thrive in such a
vast array that just isolating significant
numbers of specific ones was, until now,
a tedious-even daunting-task. And

Agricultural Research/March 2000

.- ...

that was just a first step toward iden-
tifN ing the microbes and the odors the\
Taking a thorough census should soon
be easier, using research tools like DNA
sequence analysis, diagnostic probes,
and a fluorimaging analysis, says Cotta.
He, with microbiologist Terence R.
Whitehead and postdoctoral micro-
biologist Cherie
J. Ziemer, are de-
veloping a way to
extract the DNA
from all the microbes in a waste slurry
sample and, in one fell swoop, detect and
measure the prevalence of the many
genera, species, and strains of the
What causes the rise or fall of
populations of microbes that are the real
stinkers? To find answers, the scientists
have taken waste samples from one farm
that specializes in feeder pig production;
now they're examining samples from
other farms where swine of different ages
are fed different feeds. "As we continue,
we'll compare our data on microbes with

To isolate bacteria present in swine waste samples, microbiologists Rhonda
Zeltwanger and Michael Cotta work in an anaerobic glove box. Because
most of these bacteria are strict anaerobes, many manipulations must be
performed in the absence of oxygen.

Agricultural Research/March 2000

-..-*--.: :. +_+ ,+'+ .- m

the findings of our ARS colleagues at
Ames. Iowa, who are analyzing odors cro
from air samples near livestock odorproditcorst
operations." says Cotta (See "Measuring may be somewII
Odors From Li\estock Operations." Techniquesdevel.
.Agricultural Research. April 1998. p. may be used to learn'itao
24., pathogens and anAtbiot
So far. the researchers have found that crobes survive in stored iMiar
the most common bacteria in fresh s\\ ine crobes of particular interest wre-tikto
include Escherichia
coli and species of
Ben Hardin, ARS.
manure include those in the genera This research is part of Manure and
Clostridium, Lactobacillus, and Rumino- Byproduct Utilization, an ARS National
coccus, while the most common in swine Program (#206) described on the World
waste pits include a mix of Clostridium, Wide Web at http://www.nps.ars.
Streptococcus, and Peptostreptococcus. usda. gov/programs/nrsas.htm.
Although the scientists are focusing Michael A. Cotta, Terence R. White-
on the pit storage environment, what head, and Cherie J. Ziemer are at the
they learn may be applied to research on USDA-ARS National Center for Agri-
manure that is composted or processed cultural Utilization Research, 1815 N.
through lagoons. University St., Peoria, IL 61604; phone
Soon the researchers will be crank- (309) 681-6273, fax (309) 681-6686, e-
ing out large numbers of diagnostic mail
probes to inventory microbes in manure
samples from different environments. +

Gourmet Feed


ARS entomologist Eric Jang (left) and
Stuart Stein, director of the USDA-APHIS
Hawaii Fruit Fly Rearing Facility, examine
a spent larval diet before shipping it to
livestock yards where it will be fed to cattle.

,tuart tein (lett) ana Eric Jang inspect a
larval diet for medflies.

rearing of Mediterranean fruit
flies make a good feed for
livestock, according to ARS
and university researchers in
Hawaii. Their investigations could help
convert a costly environmental problem
into a new supplement for cattle or oth-
er animals.
To fight outbreaks of the Mediterra-
nean fruit fly, or medfly, states like
California and Florida rely on shipments
of millions of sexually sterile medflies
reared in laboratories. A medfly factory
run by USDA's Animal and Plant Health
Inspection Service (APHIS) in Waiman-
alo, Hawaii, for example, supplies some
300 million sterile medflies every week
for medfly control in the Los Angeles
basin. When these
sterile males mate SCOTT BAUER (K8758-1)
with wild medfly fe-
males, no viable off-
spring result-and the
population dies out.
For part of the time
when the medflies are
growing at the mass-
rearing facility, they Medfly larvae con
eat a nutritious mix- a highly nutritious
ture of water, milled based diet.
wheat bran or milled
corn cobs, wheat germ, sugar, and yeast.
The diet is caramel-to-brown in color
and looks something like moist sawdust
or dried oatmeal.
Once the mix is no longer needed to
nourish the insects, APHIS pays about
$100,000 a year to dispose of the used
or "spent" medfly diet. The Waimanalo
plant generates about 12,000 pounds of
this material every day. Getting rid of it
is an environmental and economic prob-
lem, according to Waimanalo director
Stuart H. Stein.
Now, ARS scientists and their Uni-
versity of Hawaii colleagues have shown
that spent diet can be used as livestock
feed. The researchers determined the
amount of protein, fat, carbohydrate,
minerals, and other nutrients in spent diet


from the APHIS facility and two other
rearing labs in the state. Their tests with
cattle and sheep showed that it is safe to
eat and highly digestible.
Harvey T. Chan, now retired from
ARS, and Eric B. Jang of the ARS U.S.
Pacific Basin Agricultural Research
Center in Hilo, collaborated in the re-
search with James R. Carpenter, Ruth Y.
Niino-DuPonte, Harry M. Ako, and
Halina A. Zaleski of the University of
Hawaii College of Tropical Agriculture
and Human Resources.
The idea of recycling medfly diet isn't
new. University scientists, for example,
fed it to pigs for a study in the 1980s. In
addition, some foreign labs that rear
medflies already recycle their leftovers
as feed. But the new studies are appar-
ently the first to provide
the data needed for a
commercial trial with
cattle in Hawaii.
The North Shore
Cattle Company on the
island of Oahu now has
an agreement with the
Waimanalo factory to
ning receive all of the used
rn- diet that it can provide,
according to Stein. Uni-
versity scientists will
monitor the effect of the new rations on
the cattle weight gains that are essential
for a profitable herd.
Spent diet has the potential to replace
10 to 15 percent of the feed that Hawaii's
livestock producers buy from other
states as a supplement for their ani-
mals.-By Marcia Wood, ARS.
This research is part of Crop Protec-
tion and Quarantine, an ARS National
Program (#304) described on the World
Wide Web at http//www.nps.ars. usda.
gov/programs/cppvs. htm.
Eric B. Jang is with the USDA-ARS
U.S. Pacific Basin Agricultural Re-
search Center, Stainback Hwy., P O. Box
4459, Hilo, HI 96720; phone (808) 959-
4300, fax (808) 959-4323, e-mail +

Agricultural Research/March 2000

A Unique Potato Virus Collection

If a plant pathologist, breeder, geneticist, or grower discov-
ered an unusual viral disease in a potato crop, where could that
person go to identify the culprit?
One good place to check would be the Agricultural Research
Service's Schultz Potato Virus Collection, named after ARS
plant pathologist Erwin S. Schultz. He and plant pathologist
Donald Folsom, with the Maine Agriculture Experiment Station,
started this collection in 1916 at Aroostook State Farm at
Presque Isle, Maine.
Researchers throughout the world have compared their
infected potato plants with those maintained in the Schultz
collection. Even now-after more than 80 years-the collection
still contains progeny from the original infected plants.
Names given to the infectious diseases maintained in the
collection were based on descriptive symptoms of so-called
degeneration diseases of potato hosts. Scientists showed that
diseases such as Aucuba mosaic, calico mosaic, latent virus,
leaf rolling mosaic, mild mosaic, rugose mosaic, and severe
mosaic are viral in nature.
In 1971, ARS researchers determined that a viroid was the
cause of potato spindle tuber disease, which previously had
been identified as a virus. Materials from the Schultz potato
virus collection were used to identify these pathogens.
Plant pathologist Robert W. Goth, who has been curator since
1968, maintains the collection, now housed at Aroostook Farm
and at ARS' Vegetable Laboratory in Beltsville, Maryland.
"Since 1930, viral reactions of many potato cultivars released
jointly by USDA and cooperating agencies were evaluated us-
ing samples from this collection," says Goth.
Viruses are maintained in plants grown in insect-proof cages
to avoid contamination and loss of original viruses. Each year,
the virus-infected plants are grown out in these small, screened
cages in the field to keep the collection going for future use.
Goth saves four tubers from each cage for replanting at Presque
Isle the next year and sends the remaining tubers to Beltsville
for further use and study. All of the potato viruses in the
collection are those most prevalent in the United States, Canada,
and Europe.
"Interestingly," says Goth, "some pathogens in the collection
affect not only potatoes, but other crops as well." Potato virus
Y, for example, which can be spread by aphids, also affects
tobacco, tomatoes, peppers, and many other plants.
"The collection continues to grow," Goth notes. A new Car-
la virus-isolated from the potato variety Red Lasoda in 1992
and named "potato latent virus" in 1998-was added to the
collection this year. Researchers can request samples of any
virus in the collection.-By Tara Weaver-Missick, ARS.
Robert W Goth is with the USDA-ARS Vegetable Laboratory,
Rm. 240, Bldg. 10A, 10300 Baltimore Ave., Beltsville, MD
20705-2350; phone 301-504-5953, fax 301-504-5555, e-mail *

Agricultural Research/March 2000

Curbing Wind-Blown Dust

"We can watch the wind pick up soil, carry it in clouds
miles above the ground, and then deposit dust over urban areas
where it can cause respiratory problems," says ARS agricultural
engineer Keith E. Saxton.
Saxton is speaking about a new computer prediction model
for the Pacific Northwest's Columbia Plateau region. The
model simulates dust storms from beginning to end by linking
smaller models for wind erosion and dust emissions. Saxton
and about 15 colleagues developed the model as part of the
Northwest Columbia Plateau Wind Erosion/Air Quality
The scientists are with ARS and Washington State Univer-
sity in Pullman and the University of Idaho at Moscow. They
tested the model on a 50,000-square-mile section of the Co-
lumbia Plateau, using several previously recorded dust storms.
For those studies, "dust" was defined as particulate matter
less than 10 micrometers in diameter-or PM-10. These
particles are small enough to be drawn into the lungs. But more
recent concerns about health problems have put the greatest
focus on particles smaller than 2.5 micrometers-PM-2.5.
Often, about a third of the windblown soil particles caught
in samplers are PM-2.5 in size. Other PM-2.5 sources include
smoke from fireplaces, smokestacks, and fields that farmers
burn to stop soilborne crop diseases.
"The Columbia Plateau is one of the world's largest areas
of wind-blown volcanic soils," Saxton says. "These soils are
extremely light and prone to forming dust clouds."
Farmers on the plateau typically grow winter wheat every
other year. In the "off" year they leave the land bare to save
soil moisture. But ARS agronomist Frank L. Young and sev-
eral ARS and state scientists are developing crop rotations to
keep land covered as much of the year as possible.
Saxton serves on the National Agricultural Air Quality Task
Force charged with advising the Secretary of Agriculture on
all aspects of air quality related to agriculture. This task force
was formed in 1996 as ARS was beginning to expand its re-
search on how agriculture affects air quality. Targets include
not only dust but also odors, ozone, pesticides, and ammonia
emissions from animal operations.
Following the task force's recommendations, the U.S.
Environmental Protection Agency has formally agreed to work
closely with USDA when air quality issues involve agriculture.
This will help both agencies face the environmental challenges
of the new century.-By Don Comis, ARS.
Keith E. Saxton and Frank L. Young are in the USDA-ARS
Land Management and Water Conservation Research Unit,
215 Johnson Hall, Washington State University, Pullman, WA
99164-6421; phone (509) 335-1552, fax (509) 335-3842, e-
mail ksaxton *


Zapping Airborne Salmonella and Dust

scientists have found a way to
reduce Salmonella and dust in
poultry areas. The technology
may sound commonplace, but
for many in the poultry industry it's
exciting news.
The technology uses a negative
electrostatic charge to remove dust from
the air. Unlike most air cleaners, this
device does not require air to move
through it for cleaning to occur. Reduc-
ing the dust is important, because these
particles often give hitchhiking germs a
free ride into chicks' lungs and feathers.
Bailey W. Mitchell, an agricultural
engineer, developed the ionizer system,
in cooperation with veterinarian Henry
D. Stone. Both researchers work atARS'
Southeast Poultry Research Laboratory
in Athens, Georgia. ARS applied for a
patent on the technology in July 1998.
The first industry trials began in June of
1998, and a commercial product is now
Early trials in 1994 suggested the
process would reduce dust and had the
potential to reduce airborne transmission
of Newcastle disease virus and other
disease organisms such as Salmonella.
"When Bailey first started this work,
we tested it in a small chick hatcher,"
says Stone. "He modified it many times.
When I saw the consistent reduction in
dust particles and bacteria during hatch,
I knew it had potential."
Mitchell says credit is also due to
veterinary medical officer Daniel J. King,
physiologist R. Jeff Buhr, and micro-
biologists Peter S. Holt, Richard K. Gast,
K.H. Seo, Mark E. Berrang, S. Stan
Bailey, and Nelson A. Cox for their
collaboration with this research.

Dust Spreads Disease
Keeping hatching cabinets free of
pathogens is especially important, be-
cause one infected hatching chick can
very quickly spread disease organisms to
an entire cabinet of 15,000 tiny birds.
One reason: The strong air needed to

move warmth throughout the cabinet
also moves dust.
Currently, chemical sprays are the
only effective means of reducing air-
borne disease transmission in hatching
cabinets, but they can be expensive and
can damage hatching equipment.
This electrostatic system would be
safer for poultry and other livestock. It

Agricultural engineer Bailey Mitchell
demonstrates an electrostatic air cleaning
system. The hatching cabinet used here is a
small version of ones used commercially
for hatching chicks.

would also keep dust levels down better
than existing methods and would con-
tinually clean the air of pathogens.
The Simco Company of Hatfield,
Pennsylvania, is one of the world's
largest manufacturers of electrostatic
equipment. Mitchell says the company
provided electrostatic insights, equip-
ment, and instrumentation under a
federal-industry cooperative research
and development agreement.
"It makes sense that reducing the fluff
in the hatching cabinet would reduce
bacterial contamination at pipping," says

Hank Engster, vice president of techni-
cal service for Purdue Farms of Salisbury,
Maryland. Pipping is when the chick
breaks through its shell during hatching.
"We are pursuing a test of the tech-
nology at one of our complexes on the
Delmarva Peninsula," says Engster.
Experiments conducted in a small
chamber with agar plates exposed to a
continuous Salmonella aerosol showed
that high levels of charge can, on average,
reduce airborne Salmonella levels from
over 1,000 per plate to near 0 in what
appears to be an instantaneous sterilizing
The electrostatic technology consis-
tently reduced Salmonella transmission
between chicks by 98 percent and
reduced Salmonella in air samples by 95
percent in a room with Salmonella-
infected egg-laying hens.
In other tests, Mitchell built up hatch-
ing cabinet dust levels to 40 times above
normal. The device reduced airborne par-
ticles by 99 percent in 60 seconds.
The system was tested on a hatching
cabinet with a few infected fertile eggs
interspersed among healthy ones. Salmo-
nella counts in the guts of 7-day-old
chicks in the cabinet with the device were
reduced by a factor of 1,000- to 10,000-
fold, when compared to counts in chicks
in a hatching cabinet without the device.

Producers May Flock to Air Cleaners
"We are mainly interested in the tech-
nology for food safety-but also for im-
proved growth and productivity in our
flocks," says Purdue's Engster. "We sent
a group down to Athens, Georgia, to
assess how well the technology would
meet our needs. Bailey showed us a
system installed at Seaboard Farms."
Seaboard Farms in Athens supplies
poultry for many fast-food companies.
The company, with four hatcheries, pro-
duces over 5 million chicks a week.
Installing the ARS ionizer costs about
$2,500 per hatching cabinet. Seaboard
Farms hopes to install it in all of the cab-
inets in one hatchery.

Agricultural Research/March 2000

"We tested the technology at our
hatcheries," says Steve Bolden, vice
president of live production at Seaboard
Farms. "We found it reduced bacteria in
three out of five tests and consistently
kept dust levels down. We have
negotiated with ARS to license the
In addition, hatchability-the percen-

tage of eggs that
produce live chicks-
increased as much as

modifications to better fit their hatching
"Initial tests in poultry production
look promising in terms of improved
vitality and health of flocks," says
Knapp. "If we can verify reduced levels
of bacteria, we think the technology
would be a vital component to our
overall live production health programs."

The petri dishes below show sterilization effects of negative air ioni
chamber aerosolized with Salmonella enteritidis. The left sample

2.7 percent in tests of
the system, thanks to
reduced pathogens, Mitchell says.
"Multiply this seemingly modest
increase by the millions of hatching eggs
farmers sell and you can see the
The technology has also interested
turkey producers. Wampler Foods of
Harrisonburg, Virginia, the seventh larg-
est U.S. broiler chicken producer and
third largest turkey producer, invited
Mitchell to demonstrate the technology.
Wampler is interested and would like to
install units when commercially avail-
able, according to Tom Knapp, manager
of W:innpler's [Ltrke\ brcedini opera-
tion, He a.\ I the coimpin i i.slso
planning on model

the right, treated.

According to Mitchell, numerous
simple ionizer systems have been devel-
oped and marketed for air-cleaning
applications with little or no research.
Although many of these devices had
potential in small spaces with light dust
loads, they require air to pass through
them and are not able to handle the
larger space and higher dust levels of
a typical hatching cabinet. The super-
charged ionizer/dust collection
system developed by ARS
appears able to do
the job.

The process is likely to have appli-
cations outside agriculture, Mitchell
says. In tests, the researcher removed
smoke from a 3,300-cubic-foot room
with 95-percent efficiency. Many other
companies, he adds, are asking to review
the technology for environmental and
other air-cleaning applications.-By Jill
Lee, formerly with ARS.
This research is part
zation on a of Animal Health, an
is untreated; ARS National Program
(#103) described on
the World Wide Web at
usda. gov/programs/appvs. htm.
Bailey W Mitchell and Henry D.
Stone are with the USDA-ARS Southeast
Poultry Research Laboratory, 934 Col-
lege Station Rd., Athens, GA 30605;
phone (706) 546-3443 [Mitchell], (706)
546-3431 [Stone], fax (706) 546-
3161, e-mail baileym@bae. *

Agricultural Research/March 2000

S ..

a, -

PEGGY GREB (K8707-1)

Parasitic varroa mites
attached to a sticky board
removed from the bottom
of a beehive.


u~ I:* :
~~. .5

Battling the varroa mite has become a sticky job-
literally. Entomologist Jeff Pettis, who is with the ARS
Bee Research Laboratory in Beltsville, Maryland, has
been looking for a way to snag mites that have been
threatening honey bees for years. Through his exper-
iments with sticky paper, a nonchemical control method evolved.
The mites, which attach to and feed on bees, can become
dislodged through the bee's self-grooming or from smoke and
chemical treatments applied by beekeepers. Pettis used sticky
paper at the bottom of bee colonies to collect the dislodged
mites for experiments.
"We noticed that many of the mites on the sticky paper were
still alive and that they could easily reattach as the bees re-
entered the colony and
walked across the bottom PEGGY GREB (K8708-1)
board," said Pettis. As a re-
sult, he created something
called the Beltsville screen
insert to help control the
mite population.
The screen insert works
by creating a 1- to 2-inch
gap between the bottom
board and the hive bottom.
The insert's wire mesh al- '
lows the mites to fall k
through the screen and
onto the hive bottom so
they can't reattach to the
bee. Monthly samples of
the fallen varroa showed Entomologist Jeff Pettis examines a sc
that the screen insert re- from bees, thus reducing mite levels in
duced the mite popula-
tions by about 15 percent.
Though not sufficient
alone, the Beltsville screen
insert can contribute to integrated pest management practices.
Honey bees produce $270 million worth of honey, beeswax,
and other hive products and pollinate nearly $10 billion worth
of crops annually. So their conservation is of national and in-
ternational importance. Improved varroa mite control will be
valuable to people involved in the U.S. beekeeping industry,


including hobbyist and commercial beekeepers who rent their
colonies for pollination services.
Researchers are continually developing and improving the
screen, but it's already being advertised for sale.
"It's wonderful to be working with Beltsville scientists in
selling a product that keeps us from having to rely totally on
chemicals," says Steve Forrest of Brushy Mountain, a bee-
keeping supply company in Movarian Falls, North Carolina.
Forrest says the screen is selling very well and hasn't generat-
ed any returns or complaints from beekeepers.
Varroa mite infestations have become such a serious
problem that maintaining bee colonies without chemical
treatment is virtually impossible. Currently, the only pesticide
approved for use as a para-
sitic mite control for honey
bees is Apistan-a strip
that contains the chemical
tau-fluvalinate. Varroa,
however, have begun to
show resistance to the
chemical, so scientists are
looking for alternatives
such as the screen.
As safe and effective
chemical controls contin-
ue to be researched and de-
veloped, the screen insert
will complement Apistan
in assisting beekeepers
with the control of invad-

National Program (#104)
described on the World Wide Web at http://wwnps.arsusda.
gov/programs/appvs. htm.
Jeffery S. Pettis is at the USDA-ARS Bee Research Labo-
ratory, Bldg. 476, 10300 Baltimore Blvd., Beltsville, MD
20705-2350; phone (301) 504-7299, fax (301) 504-8736, e-
mail *

Agricultural Research/March 2000

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