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 1999
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 )
Genre: federal government publication   ( marcgt )
periodical   ( marcgt )
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).
 Record Information
Bibliographic ID: UF00074949
Volume ID: VID00025
Source Institution: University of Florida
Holding Location: University of Florida
Rights Management: All rights reserved by the source institution and holding location.
Resource Identifier: ltuf - ABP6986
oclc - 01478561
alephbibnum - 000271150
lccn - agr53000137
issn - 0002-161X

Full Text
U.S. Department of Agriculture


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Partnerships That
Speed Technology
to Users
Consider the constant dilemma of the
farmer: so many choices to make-and
no crystal ball to predict the various
Today's crop producer has available
many choices of improved seeds, differ-
ent methods to control pests, and ways to
improve the soil for productivity and
best nutritional environment for the crop.
But science has still not found a way to
look into the future to guid the farmer
months before the harvest on how to
choose the best practices tomaximize
iad. -----T
However, technology has improved
enough that more accurate descriptions
of problems in the field can be reported to
the farmer as soon as they occur. Think
of this as the agricultural equivalent of
just-in-time parts delivery to a car as-
sembly plant.
The cover story in this issue describes
development of technology that will al-
low farmers to receive reports on their
crop health and growth in a timely man-
ner, so they can take action to correct
problems before they get out of hand.
Receiving this information just in time
will allow the farmer to be more cost
effective by targeting use of expensive
inputs, which will limit adverse effects to
the surrounding environment.
This promising line of research in-
volves USDA's Agricultural Research
Service and RESOURCE21, LLC, of
Englewood, Colorado, working under a
cooperative research and development
agreement (CRADALThis partnership
links a team of scientists from six ARS
locations with four private companies in
multidisciplinary systems research re-
quired to build the framework for the
farm manager. It will provide accurate
information while there is still time to
apply a correction.

The agreement allows experts in sci-
ence, production agriculture, and mar-
keting to build the complex information
system needed to make precision agri-
culture a real-time working tool.
ARS scientists have used CRADAs to
expand expertise and speed development
of many technologies that are now used
by farmers or found in the grocery store.
For example, the oil from a new crop,
meadowfoam, is now in great demand
for use in specialty cosmetics and indus-
trial lubricants because of a patent li-
cense and CRADA. In 1998, ARS signed
the 800th agreement, and this total should
reach 1,000 in the year 2000.
CRADAs have provided a new means
to develop ARS discoveries by provid-
ing an opportunity for the public sector to
partner with private companies to maxi-
mize each other's strengths. This has
proven to be a win-win-win scenario.
Working with RESOURCE21 has pro-
vided additional expertise and resources
to ARS that have accelerated this re-
search program. For the companies, it
has allowed them to test their results
against real field conditions in a variety
of different growing areas. And it will be
a win for the farmers when applied to
their unique situations.
CRADAs were authorized by the Fed-
eral Technology Transfer Act of 1986 as
a way of enhancing the ability of federal
research laboratories to work with indus-
try to commercialize technology. These
agreements are unique in that the cooper-
ator is granted the right to negotiate an
exclusive license in a defined field of use
for government-owned inventions made
under the agreement. In addition, infor-
mation developed under the agreement
may be treated as confidential for up to 5
These provisions have provided the
incentive to encourage private-sector
partnerships to develop ideas that are
high risk and/or unproved in the market-
place. The ARS Office of Technology
Transfer (OTT) negotiates about 100 new
CRADAs each year. Currently, there are

nearly 300 active CRADAs, or more than
15 per 100 research scientists-a level
that is among the highest in government.
It is widely recognized that an impor-
tant consideration in technology devel-
opment is "industry pull"; that is, the
degree to which industry is ready or will-
ing to use the new technology. CRADAs
provide a pull incentive for companies to
approach ARS scientists with proposals
for partnerships long before a technolo-
gy is ready for patenting, or even before
it has been confirmed that an idea will
Because both partners bring value to
the project, ARS gains access to exper-
tise, facilities, equipment, and propri-
etary information, processes, and
products that would not otherwise be
available. This allows ARS to develop
critical technologies that it cannot do
alone and to get an idea to the market
much sooner.
In fiscal year 1998, CRADAs brought
in over $6.2 million in cash to ARS. More
important is the agency's additional op-
erating funds because of in-kind contri-
butions by cooperators.
The decision of ARS to enter into a
CRADA is neither automatic nor arbi-
trary. Each one is reviewed by scientists,
line managers, national program mana-
gers, and OTT. The primary decision
factor is whether the partnership will
enhance the transfer of technology for
the ultimate benefit of the tax-paying

Richard M. Parry, Jr.
ARS Assistant Administrator for
Technology Transfer Research

Agricultural Research/March 1999

March 1999
Vol. 47, No.3
ISSN 0002-161X

Agricultural Research is published monthly by
the Agricultural Research Service, U.S. Depart-
ment of Agriculture (USDA). The Secretary of
Agriculture has determined that this 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, Education, and Economics
Floyd P. Horn, Administrator
Agricultural Research Service
Sandy Miller Hays, Director
Information Staff
Editor: Lloyd McLaughlin (301) 504-1651
Assoc. Editor: Linda McElreath (301) 504-1658
Art Director: William Johnson (301) 504-1659
Photo Editor: Anita Daniels (301) 504-1609
Staff Photographer: Scott Bauer (301) 504-1607
Information in this magazine is public property
and may be reprinted without permission. Non-
copyrighted photos are available to mass media in
color transparencies. Order by photo number and
date of magazine issue.
Agricultural Research magazine articles and pho-
tographs are posted on the World Wide Web month-
ly at
Subscription requests should be placed with New
Orders, Superintendent of Documents, P.O. Box
371954, Pittsburgh, PA 15250-7954. See back
cover for ordering information.
Complimentary 1-year subscriptions are available
to public libraries, schools, USDA employees,
and the news media. Send requests or comments
to: Editor, Agricultural Research, 5601 Sunny-
side Ave., Beltsville, MD 20705-5130. E-mail
This magazine may report research involving pes-
ticides. It does not contain recommendations for
their use, nor does it imply that uses discussed
herein have been registered. All uses of pesticides
must be registered by appropriate state and/or
federal agencies before they can be recommended.
Reference to any commercial product or service
is made with the understanding that no discrimi-
nation is intended and no endorsement by USDA
is implied.
The U.S. Department of Agriculture prohibits
discrimination in all its programs and activities
on the basis of race, color, national origin,
gender, religion, age, disability, political beliefs,
sexual orientation, and marital or family status.
(Not all prohibited bases apply to all programs.)
Persons with disabilities who require alternative
means for communication of program informa-
tion (Braille, large print, audiotape, etc.) should
contact USDA's TARGET Center at (202) 720-
2600 (voice and TDD).
To file a complaint of discrimination, write:
USDA, Director, Office of Civil Rights, Room
326-W, Whitten Bldg., 14th & Independence
Avenue, SW, Washington, DC 20250-9410, or
call (202) 720-5964 (TDD). USDA is an equal
opportunity provider and employer.

Agricultural Research

Researchers Capture "Ground Truth" 4

Understanding Sugar Transport in Plants 9

Premier Bacteria Suppress Wheat Take-All 1 0

Fast Tests for Campylobacter 1 3

Natural Plant Extracts Might Sub for Methyl Bromide 14

Foiling Watermilfoil 1 6

Vaccinating Hens at the Right Time Saves Eggs 1 7

UNMASKED: A Karnal Bunt Fungus Look-Alike 18

Delta MSEA Benefits Local Ecology 20

Seeking New Controls for Costly Nematodes 22

Moms' Low Copper Could Harm Newborns 24

A Snapshot of Blood Homocysteine Levels 25

Trap Crops Prove Irresistible to Diamondbacks 26

Science Update 27

COVER: Images generated from data gathered from airplanes or satellites can give
farmers detailed information about their crops. This farm on Maryland's eastern
shore was scanned from an altitude of about a mile and a half in June 1998. Crop
variability in the field of mature wheat at left of center shows as blue and pale-
green areas, while yellow and red mark stands of weeds. In the field on the right,
where new corn is just emerging, colors indicate variations in soil types and
vegetative cover. Image by 3DI, LLC, of Easton, Maryland.

In the next issue!

0 The National Park Service will get a special gift this year: 500
new cherry trees propagated from the original Japanese cherries
presented to the U.S. government in 1912.

0 Scientists are transforming insects using green fluorescent
protein from jellyfish and gene vectors named "piggyBac" and

> Taiuia-it's a potent feeding stimulant that drives some
insects wild-and it could be just the right ingredient to make
pest-control formulations irresistible.

Agricultural Research/March 1999



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Agricultural Research/March 1999

Multi-Location Measurements Confirm Data From Aerial Observations


armers will soon be able to get a
bird' s-eye view of the "back for-
ty" with a single click of their
computer mouse.
That's the goal of Agricultur-

al Research Service scientists and pri-
vate industry cooperators
working together under one of KEITH WEL
the largest cooperative research
and development agreements
(CRADAs) in the history of
the USDA research agency.
The project aims to provide
farmers with satellite-based
information on the health of
their crops so they can apply
spot-specific remedies and
improve longer term manage-
ment practices.
Englewood, Colorado-ARS'
CRADA partner-plans to
launch up to four satellites de-
voted to remote sensing for
farmers. [See also "Orbiting
Eye Will See Where Crops
Need Help," Agricultural Re-
search, April 1996, p. 12.]
"Our job is to help develop
and refine the software that
interprets the satellite data,"
says James S. Schepers, the
ARS CRADA coordinator for
the project. Schepers leads the
research team at the ARS Soil
and Water Conservation Re-
search Unit in Lincoln, Ne-
braska. A
ARS ph
Four private companies and while A]
six ARS laboratories are par- center, I
ticipating. Companies include operates
The Boeing Company, an air- the sam
craft maker in Seattle, Wash-
ington; Farmland Industries,
Inc., a national agriculture co-
operative based in Kansas City, Missou-
ri; Marconi Integrated Systems, Inc., a
remote sensing firm from San Diego,
California; and the Institute for Technol-
ogy Development, Inc., a nonprofit com-
pany in Ridgeland, Mississippi.

ARS received more than $900,000 for
research at laboratories in Lincoln;
Shafter, California; Phoenix, Arizona;
Ames, Iowa; Beltsville, Maryland; and
Lubbock, Texas.
Once the technology is in place, Farm-

ysical sciennst iviiKe ncniemmer (leIt) cnecKs a soil s
RS soil scientist Dennis Francis withdraws another.
University of Nebraska graduate student Shannon O
Sa GPS device that allows them to relate aerial imag
pling sites.

land Industries wants to deliver it to
600,000 farmer-members. The farmer-
owned cooperative has 1,500 local co-op
associations in 25 states, and each asso-
ciation has at least one farm supply store.
Trained experts at these outlets would

use the satellite-based system to further
help farmers.
"We want technology that makes
money for farmers," says Gary W. Col-
liver, director of agronomy services at
Farmland. "We're looking at the whole
package. Remote sensing com-
plements other information,
such as soil data collected by
farm consultants."
Colliver adds that there are
other uses for remote sensing
besides crop monitoring-for
example, evaluating on a large
S scale cataclysmic events such
as hailstorms or damage from
plant diseases or insect pests.

S To Check Data Accuracy
A To get the project under way,
a small RESOURCE21 plane
toting company-owned sen-
sors-similar to those that will
be mounted on satellites-sped
over ARS research plots in
Arizona, California, Iowa, Ne-
braska, and Texas during the
past two growing seasons.
The sensors are digital cam-
eras that view crops or soil in
several bands of reflected
light-both visible and near-
infrared. The cameras record
energy as digital numbers rep-
resenting the amount of light
hitting the sensor. ARS provid-
ed data to help RESOURCE21
e convert the digital numbers to
In the numbers that represent surface
sborne properties like reflectance. The
es to company can use these reflec-
tance numbers to create maps
for farmers that represent crop
and soil conditions. ARS also
helped ensure the accuracy of
the computer programs that produce the
To represent field conditions, ARS
researchers took detailed, systematic
measurements of crop growth and devel-
opment. Called "ground truth," these

Agricultural Research/March 1999


measurements-captured by more than
a dozen different kinds of scientific in-
struments-determine how well the im-
agery in digital format correlates with
scientists' on-foot field measurements.
Thanks to day after day of clear, sun-
ny skies, research fields of California
cotton were the most intensively scruti-
nized of any in the 1997 field tests. One
intent of the in-air and on-ground obser-
vation in California was to reveal how
quickly the imagery could detect and
track cotton plants when they emerged
from the soil.

To Sound an Early Warning
That information is critical, says ARS
plant physiologist Stephan J. Maas, be-
cause the imagery could alert farmers to
problems in time for them to take action.
Maas and colleague William R. DeTar
conducted the tests at ARS' Western
Integrated Cropping Systems Research
Unit in Shafter.
"Our results," says Maas, "indicate
that the imagery is sufficiently accurate
to perceive whether the crop is coming
up well enough for the grower to let it
continue for the rest of the season-or
whether it is coming up so poorly the
grower needs to replant while there's
still time.
"Later in the season," Maas adds, "the
imagery can tell you if gaps are appear-
ing in the plant canopy. Because the
imagery is keyed to global positioning
satellites, you can get the exact coordi-
nates of the trouble spot in the field. You
can find out if there is something wrong
with your irrigation system, or if insects
are attacking the crop, or if there's some
other type of problem."
One of the tougher tests for the com-
puters analyzing the image data was to
correctly differentiate dark soil-wetted
by a weekly furrow irrigation-from
dark-green, healthy leaves of the canopy.
For this task, the mathematical models
that tell the computer how to interpret the
imagery may need to be fine-tuned. Oth-
er conditions also affect the ability of the

AKN physical scientist naries waltnan (trgnt) ana wiliam iternara, director or remote
sensing for 3DI, LLC, a geographic technologies company in Easton, Maryland, adjust an
airborne hyperspectral sensor used in imaging crop and soil conditions.

imagery to capture an accurate picture.
"Every time the plane flies, the posi-
tion of the sun and amount of atmospher-
ic haze and visibility are different," says
Susan Moran, an ARS soil scientist at the
U.S. Water Conservation Laboratory in
Phoenix. "This renders each image slight-
ly different from the previous one, wheth-
er or not the soils or crops have changed.
Users need a way to compare only those

variables that relate to crop health."
So Moran and ARS colleagues Paul J.
Pinter, Jr., Edward M. Barnes, and Tho-
mas R. Clarke developed tools that com-
pensate for these extraneous factors. One
was a calibration procedure that changes
the digital numbers to reflectance values
that represent surface conditions more
accurately and consistently from one
image to the next.

Agricultural Research/March 1999

"We can look at more variables and situations in a simulation than we
could experimentally."-Craig S. Daughtry

First they calibrated the camera out-
put against an object of known reflec-
tance-a surprisingly tricky task. Moran
placed commercially produced canvas
tarps at the field sites. The tarps are
chemically coated to produce a specific
Then Moran's team developed equa-
tions that convert the digital numbers to
numbers that represent the reflectance of
a given image. Normal manufacturing
processes and exposure to harsh field
conditions cause tarp variability that re-
quired Moran to produce a unique equa-
tion for each tarp. She also had to teach
the users how to place the tarps on the
ground and how to clean and store them
to ensure accurate readings.
"If a tarp is dirty, its reflectance can
change by up to 70 percent," Moran says.
The calibrations compensated for at-
mospheric conditions, but images still
couldn't be compared-because the
viewing angle could differ for each flight,
skewing the results.
"If you look straight down on a crop,
getting what's called a nadir view, you
might see that it has 50 percent plant
cover," says Moran. "But if you look at
the same crop from an oblique angle, it
could incorrectly appear that there is
almost 100 percent plant cover."
To solve this problem, former ARS
physical scientist Jiaguo Qi developed a
simple-to-use computer program that
converts the reflectance from any view-
ing angle to the standard nadir view.
RESOURCE21 has already started using
both the tarps and the model.

To Account for Variation
Researchers at the ARS labs in Ames
and Beltsville are also working to com-
pensate for environmental variables.
For example, scientists led by ARS
plant physiologist Jerry L. Hatfield at the
National Soil Tilth Laboratory in Ames
are designing statistical techniques to
interpret what's known as temporal vari-
ation-the patterns of change seen in
aircraft and satellite images over time.

By viewing the same fields as those
scanned by the remote sensors, scientists
are able to determine the patterns of the
soil color and topography and crop
growth. The researchers then analyze the
patterns for clues about soil conditions
and crop growth over the growing season.
This will allow farmers to pinpoint
specific problem sites in a field and apply
nutrients and pesticides only where
At the ARS Remote Sensing and Mod-
eling Research Laboratory in Beltsville,
research agronomist Craig S. Daughtry

why one area may look greener than
But instead of direct experimentation,
the scientists are simulating crop and soil
reflectances using computer models. To
test their models, they obtain data from
3DI, LLC, a geographic technologies
company in Easton, Maryland, that uses
airborne hyperspectral sensors to scan
target areas.
"We can look at more variables and
situations in a simulation than we could
experimentally," says Daughtry. "Our
modeling efforts should tell us what kind

Sara Loechel, a remote sensing researcher at the University of Maryland, labels fields,
woodlands, and streams on a computer, while ARS agronomist Craig Daughtry locates the
same features on an aerial photograph of the Beltsville [Maryland] Agricultural Research
Center. The computer image will form the base layer of a geographic information system
map. Other data about soils, crops, and management practices will be added, along with
remotely sensed images of crops to update their growth and development.

and physical scientist Charles L. Wal-
thall are examining digitized images for
spatial variability-the differences in
height, plant growth, and appearance from
one part of the field to another. They're
also analyzing spectral properties, or the
differences in color within a field and

of differences the sensors can detect,
such as how small a change in leaf area or
color could be discerned. This informa-
tion will help us determine the best light
wavelength bands to use to interpret soil
and crop conditions over the growing
season," he says.

Agricultural Research/March 1999

To Detect Yield-Limiting Factors
ARS scientists in Lubbock and Lin-
coln are testing remote sensing's ability
to detect conditions such as water stress
and nitrogen deficiency that can reduce
crop yields.
In 1998, the second year of trials in
Lubbock, a sensor-equipped plane flew
over cotton- and cornfields every day to
view the effects of the worst April-
through-July drought in Texas High
Plains history. The project's scientists
were able to test remote sensing of nitro-
gen deficiencies in crops under extreme-
ly dry, as well as fully irrigated, condi-
"The drought and high air tempera-
tures were so bad," says Dan R. Up-
church, "that when we cut back on irri-
gationby only a third, we grew 80 percent
less corn.
"But it was a good year for remote
sensing trials because we nearly always
had clear skies for aerial viewing of plants
under extreme drought conditions." Up-
church leads research at the ARS Crop-
ping Systems Research Laboratory in
The scientists compared two levels of
watering in both corn and cotton to see
how reduced watering affected crops
during a severe drought. For each water
level, they tested five levels of nitrogen
fertilizer application.
To verify the aerial readings, Upchurch
and agricultural engineer Donald F.
Wanjura took ground measurements such
as leaf water potential, a measure of how
tightly water is held in leaf tissue. They
also collected data from a field weather
station and a set of infrared thermome-
ters that measure leaf temperature. They
took light reflectance measurements of
the fields with a boom-mounted camera
perched above the canopy.
The purpose of the experiment was to
see whether cameras can detect plant
nitrogen deficiency before visible signs
appear, under both dry and wet condi-
Lincoln researchers are working to

Soil scientist Dennis Francis compares soils collected at an ARS Management Systems
Evaluation Area (MSEA) in Shelton, Nebraska. The project looks at water and nitrogen
stress in corn and at water stress in soybeans.

develop signatures-sort of like finger-
prints made of the different light wave-
lengths-to indicate nitrogen deficiency
or water stress.
"For each area, a different stress may
predominate," says Lincoln's Schepers.
"In Texas, that's water. In Nebraska,
nitrogen is of more concern," he says.

A Beneficial Relationship
Richard Baumeister, director of prod-
uct development for RESOURCE21,
values ARS' nationwide network of lab-
oratories, which allows widespread geo-
graphic testing-plus ARS expertise in
research and validating remote-sensing
data on the ground.
"ARS scientists know how to set up
nitrogen and drought-stress experiments,
while we provide the aerial imagery that
is helpful to those experiments,"
Baumeister says.
"This is a mutually beneficial rela-
tionship," he continues. "We want to
enhance the management practices of
farmers so they make the best possible

yields. Sure, we want to make money,
but we can't do that if the farmers don't,
David G. Mohr, RESOURCE21's di-
rector of new business development, adds,
"We rely on ARS to make our research
reliable and credible. ARS helps us fol-
low the proper research protocol to test
our products, making sure our results are
valid and applicable to the entire coun-
try."-By Kathryn Barry Stelljes, Don
Comis, and Marcia Wood, ARS. Dawn
Lyons-Johnson, formerly with ARS,
contributed to this article.
This research is part of Integrated
Farming Systems, an ARS National Pro-
gram described on the World Wide Web
grams/207s2. htm.
For more information on this project,
contact James S. Schepers, USDA-ARS
Soil and Water Conservation Research
Unit, 119 Keim Hall, University of Ne-
braska, Lincoln, NE 68583-0915; phone
(402) 472-1513, fax (402) 472-0516, e-
mail *

Agricultural Research/March 1999

Understanding Sugar

Transport in Plants

A signal system between the brain
and the stomach tells animals to
stop eating when their stom-
achs are full-or, conversely, it
lets them know when they need
more food.
Scientists for the Agricultural Re-
search Service at Urbana, Illinois, have
discovered that plants also have a spe-
cialized signaling system that regulates
nutrient distribution.
ARS plant physiologist Daniel R. Bush
says plants can regulate distribution of
nutrients via a signal system that controls
the flow of sugar from photosynthetic
leaves to nonphotosynthetic tissues, like
roots and seeds. These tissues are called
sinks, because they must import sugars
and amino acids to support plant growth
and development.
Plants convert light energy from the
sun into biochemical energy that is used
to synthesize the sugars and amino acids
through the complex photosynthetic pro-
cess. Up to 80 percent of the products of
photosynthesis are transported to sink

tissues in the plant's vascular system.
"We have known about the mechan-
ics by which the plant's vascular system
transports organic nutrients, for years.
But we didn'thave any information about
how this system is regulated," says Bush.
"What we have discovered is that su-
crose, the major form of transported sug-
ar, is also a signal molecule that the plant
responds to by increasing or decreasing
nutrient flow to sink tissues."
When sucrose departs from plant
leaves, it flows in the elongated phloem
cells that lie end to end, forming a living
conduit in the plant's vascular system. A
specialized sucrose transport protein first
described by scientists in the ARS Pho-
tosynthesis Research Unit at Urbana ac-
tively loads the sugar into the phloem.
The concentration of sucrose inside
the phloem cells is up to 100 times great-
er than that outside. "This attracts water
into the cells and increases the hydro-
static pressure of the leaf phloem," says
"When sucrose is released from the


As part of a test of a recently discovered signalling system that regulates nutrient
distribution, plant physiologist Daniel Bush chills young sugar beet leaves to block the flow
of sucrose in phloem cells.

Plants convert light
energy from the
sun into biochemi-
cal energy that is
used to synthesize
sugars and amino
acids through the
complex process of

phloem cells in sink tissues, water also
leaves the cells, creating a hydraulic pres-
sure difference between the leaf and the
sink phloem. That pressure difference
causes a mass flow of solution through
the phloem. In many ways, this is very
similar to the pressure-driven flow of
blood pumped through the human body,
says Bush.
By learning more about how plants
allocate photosynthetic products, scien-
tists may be able to modify plant growth
to increase yields, alter nutritional value,
or overcome environmental challenges
such as elevated carbon dioxide levels.-
By Dawn Lyons-Johnson, formerly with
This research is part of Improving
Plant Biological and MolecularProcess-
es, an ARS National Program described
on the World Wide Web at http://
Daniel R. Bush is in the USDA-ARS
Photosynthesis Research Unit, 190
PABL, University of Illinois, 1201 W.
Gregory, Urbana, IL 61801; phone (217)
333-6109, fax (217) 244-4419, e-mail *

Agricultural Research/March 1999






Inside a growth
technician Kurtis
examines plants
grown in soil
samples collected
from long-term
fields in nine states.

t was the fifth consecutive time that
plant pathologists Jos M. Raaij-
makers and David M. Weller grew
wheat seedlings in soil they'd col-
lected from Lind, Washington. The soil
was special, but not unique-similar soils
had been found worldwide. These soils,
on which only wheat had grown year
after year, naturally suppressed the fun-
gus that causes one of the world's worst
wheat diseases: take-all.
The scientists, working for USDA's
Agricultural Research Service, were try-
ing to identify why wheat thrived in these
soils when, in most places, it succumbed
to the ravages of take-all. The Gaeuman-
nomyces graminis fungus blackens plant
roots and can reduce yields by 50 percent
or more, costing U.S. wheat growers
millions of dollars annually.
Weller is a plant pathologist in the
ARS Root Disease and Biological Con-
trol Research Unit at Pullman, Washing-
ton. Raaijmakers, formerly a plant
pathologist with ARS, is now an assis-
tant professor at Wageningen University
in the Netherlands.
The researchers succeeded-and
more. They discovered that specific
strains of bacteria possess extraordinary
abilities to reproduce on roots and fight
the disease. Their discoveries not only
give new hope for take-all control, they
may have broad applications for biolog-
ical control of many diseases in a variety
of crops.
Natural suppression of take-all was
first observed more than 60 years ago. If
a wheat crop was grown every year and
no other crops were grown in the same
soil, the disease would eventually disap-
pear-or exist only at very low levels.
This phenomenon was labeled "take-all
By the 1970s, several scientists, in-
cluding ARS researchers, knew that flu-
orescent Pseudomonas bacteria were
somehow involved.
A decade ago, retired ARS plant pa-
thologist R. James Cook (now with Wash-
ington State University), Weller, and ARS

geneticist Linda S. Thomashow discov-
ered a key to the role of the pseudo-
monads. They proved that some of these
bacteria produce antibiotics and showed
that the antibiotics naturally suppress the
G. graminis fungus. And they isolated
the genes responsible for producing the
antibiotics 2,4-diacetylphloroglucinol
(Phl) and phenazine-l-carboxylic acid
The scientists also successfully trans-
ferred the antibiotic-producing ability to
other Pseudomonas strains. [For a brief
history of important research about take-
all and its control, see "Tackling Wheat
Take-All," Agricultural Research, Au-
gust 1995, pp. 4-7.]

Agricultural Research/March 1999



These findings opened the door to
using the bacteria as a biological control
for take-all. But there were still ques-
tions. Although take-all decline occurred
worldwide, there were enough differ-
ences that scientists believed many mech-
anisms were involved.
And using the Pseudomonas bacteria
to suppress take-all presented a chal-
lenge common to all biological control
efforts: how to achieve consistent suc-
"Usually, you start with very large
numbers of a biological control organ-
ism, such as a million on each plant
seed," says Weller. "But as the control
organisms compete with the hundreds of

other soil microbes for nutrients, their
population declines sharply. That gives
the fungus a chance to regain a foot-

Three Candidates Are Standouts
Weller's team discovered that nature
provided the solution. In three Washing-
ton soils that naturally suppress take-all,
they've identified three different bacte-
ria that outperform all the other microbes.
"At least in the U.S. Pacific Northwest,
there seems to bejust one mechanism for
take-all control," says Weller.
These bacteria have a specific genet-
ic fingerprint that indicates superior abil-

"These premier strains have two
unique qualities that have never been
seen in any biological control agent. They
colonize the wheat's roots very aggres-
sively, and they control disease when
applied in relatively low numbers."
Unlike other bacteria, the populations
of these premier strains decline much
less from competition with other organ-
isms. Even starting with only 10,000
bacteria on a seed, the premier strains
reproduce rapidly and soon reach the
level of millions necessary to suppress
take-all. And they stay at that level
throughout the growing season.
The bacteria's ability to reproduce so
rapidly has an enormous cost-savings

Agricultural Research/March 1999

potential. "Every factor of 10 by which
you decrease the dose, or number of
organisms applied-say from 1,000,000
to 100,000 organisms-significantly re-
duces the cost of the biological control
treatment," says Weller.
ARS has applied for a patent on the
premier bacterial strains, the genetic fin-
gerprint, and the methods for finding
similar strains in other soils. Two com-
panies plan to license the technology to
produce seed coatings or other control
methods. Farmers should start to reap the
benefits in just a few years.
"With these strains, it is possible to
control disease on as many as 1,000 acres
with only a quart of bacterial culture,"
says Weller.
The scientists have demonstrated that
in 2 to 6 years of cropping only wheat, the
bacteria's presence can change the soil
from an environment that favors take-all
to one that naturally suppresses it.
Each soil may have a different bacte-
rium that works best, but all these pre-
mier bacteria possess the same qualities.
The next step is to find the actual genes
responsible for their root-colonizing abil-
ities. In the meantime, the researchers
can enhance the bacteria by using genet-
ic technology they developed earlier.
The premier strains already produce
the Phl antibiotic. "By adding a gene, we
can transform the bacteria so they also
produce the antibiotic PCA, while re-
taining their strong reproductive and com-
petitive abilities," says geneticist
Strains that produce both antibiotics
fight two other important root diseases,
Rhizoctonia root rot and Pythium root
rot. These diseases cost millions of dol-
lars annually in lost yields and control
The transgenic bacteria are also more
potent. Only 100 to 1,000 of them are
needed per seed, compared with the
10,000 of the premier strain or the
1,000,000 typically used now for other
biological control bacteria. Thomashow
and Weller are already testing the trans-

genic organisms in the field, with ap-
proval from the U.S. Environmental Pro-
tection Agency.
Even though they're powerful, they're
safe. "There's no worry that the bacteria
will take over," says Thomashow. "They
only thrive as long as the wheat is grow-
ing, and they are part of the natural
ecosystem already."
Once these bacteria become commer-
cially available, cereal and turfgrass
growers will definitely benefit. But the
researchers believe the findings have a
much broader application.
"We've illustrated that there is a bio-
chemical and molecular basis for bio-

logical control, and this should apply to
a wide variety of diseases and crops,"
says Thomashow.
The technology, she says, is generic.
So far, each suppressive soil they've
examined contains a premier strain.
"Take-all decline has been studied ex-
tensively, but otherinstances of diseases
naturally declining in the environment
have been recorded."

Weller is especially hopeful that the
technique may be a boon to strawberry
growers as a replacement for methyl bro-
mide. This fumigant has been essential
for strawberry growers to combat soil-
borne diseases, but it is scheduled for
elimination in the year 2005. Tomatoes,
watermelon, and peas are other likely
crops to investigate.
"In each crop we've looked at so far,
there appears to be a premier strain. This
may be a universal phenomenon," Weller
says.-By Kathryn B. Stelljes, ARS.
This research is part of the ARS Na-
tional Program on Plant Sciences de-
scribed on the World Wide Web at http:/

/www. nps. ars. usda. gov/programs/
David M. Weller and Linda S. Tho-
mashow are in the USDA-ARS Root Dis-
ease and Biological Control Research
Unit, 365Johnson Hall, Washington State
University, Pullman, WA 99164-6430;
phone (509) 335-1116, fax (509) 335-
7674, e-mail *

Agricultural Research/March 1999


Visiting Russian scientist Olga Mavrodi withdraws DNA from bacteria taken from soil
infected with wheat take-all. Computer-assisted pattern analysis aids comparison of the
DNA from different samples.

Fast Tests for


wo high-tech tactics may speed
identification of Campylobacter
jejuni, the microbe responsible
for more cases of foodborne ill-
ness in the United States than
any other bacteria. Campylobacter has
turned up in eggs, raw milk, raw or un-
dercooked meat and poultry, raw oys-
ters, and contaminated water.
C. jejuni sickens an estimated 4 mil-
lion Americans every year. Of those, some
200 to 1,000 cases are fatal, according to
the U.S. Centers for Disease Control.
At the ARS Western Regional Re-
search Center in Albany, California, sci-
entists have produced two new molecular
probes that seek out and bind to C. jejuni.
Known as monoclonal antibodies, the
probes did thatjob with impressive accu-
racy in lab tests with about 20 different
varieties of bacteria.
The probes might become part of a
fast, reliable assay for identifying this
pathogen at the packinghouse, says mi-
crobiologist Robert E. Mandrell of the
Food Safety and Health Research Unit at
Albany. Or they could be packaged into
a clinical assay to help healthcare profes-
sionals identify C. jejuni when diagnos-
ing cases of gastroenteritis-an
inflammation of the stomach and intes-
What's more, the assay may help in
identifying C. jejuni associated with a
nervous system disorder, Guillain-Barr6
syndrome. C. jejuni is implicated in as
many as 30 to 40 percent of the cases of
this disease.
The probes, says Mandrell, may prove
less labor intensive and time consuming
than many assays currently used to iden-
tify C. jejuni. He developed the mono-
clonal antibody probes with colleagues
David L. Brandon and Anne H. Bates at
Albany. ARS is seeking a patent.
In related work, researcher William F.
Haddon, also in the Food Safety and
Health Unit, is investigating use of a
cutting-edge technology known as
MALDI-TOF mass spectrometry to
distinguish C. jejuni from other

Campylobacter species and from other
microbes as well. There are about a dozen
different species of Campylobacter. Of
these, C. jejuni is the most dangerous to
The sophisticated instrument that
Haddon and co-researchers Bates, Man-
drell, Leslie A. Harden, and Marian R.
Wachtel use for this approach emits a
laser beam to zap pathogen samples.
When the beam strikes the sample, pro-
teins break away from it.
Teamed with a computer, the instru-
ment can determine the weight-or
mass-of different proteins, measured
in units known as daltons. The result: a

C. jejuni specimen. But it didn't show up
in analyses of the C.fecalis, C. coli, or C.
jejuni subspecies doylei.
Key to this approach: the instrument's
precision. It can calculate protein weight
to within 5 daltons.
Besides precision, the technique also
offers the promise of speed: once a sam-
ple is prepared for analysis, results can
be ready in about 3 minutes. With further
work, this technology may yield one of
the fastest and easiest ways to correctly
identify foodborne pathogens.-By
Marcia Wood, ARS.
This research is part of Food Safety,
an ARS National Program described on

Chemist Leslie Harden uses a laser-equipped mass spectrometer to measure the weights ot
proteins in bacteria. A computer records the weight and produces distinctive profiles that
may distinguish between Campylobacter species.

distinctive fingerprint, or profile, of the
array of proteins from the zapped sam-
ple. The profile, displayed as an easy-to-
read graph generated by the computer,
may reveal the identity of the microbe.
That's what happened in preliminary
tests of four different Campylobacter
species. A protein weighing 13,724 dal-
tons, for instance, was detected from the

the World Wide Web at http://www. 08s2.htm.
Scientists named in this article are in
the USDA-ARS Food Safety and Health
Research Unit, Western Regional Re-
search Center, 800 Buchanan St., Alba-
ny, CA 94710; phone (510) 559-5610,
fax (510) 559-5948, e-mail oly @pw. usda.
gov. *

Agricultural Research/March 1999

Natural Plant Extracts Might Sub for

Methyl Bromide

perfume or flavoring.
It is, actually. But the sci-
entific name for this colorless,
nontoxic, aromatic liquid found
in essential oils of peach seeds is "benz-
aldehyde." Many such volatile oils, like
lemon, cinnamon, and peppermint, are
extracted and distilled from plants.
Naturally occurring benzaldehyde is used
commercially in perfumes, flavorings,
pharmaceuticals, and dyes.
But Charles L. Wilson, a plant pathol-
ogist at the ARS Appalachian Fruit Re-
search Station in Kearneysville, West
Virginia, has found a potential new use
for this compound. He
has been testing benz- KEITHWELLER (K8345-1)
aldehyde and other
natural plant volatiles
as possible alterna-
tives to methyl bro-
mide fumigation.
The research is
collaborative with
scientists from the
Volcani Center in Bet
Dagan, Israel, and the
for Fruit Technology
at the Fruit, Vine, and
Wine Research Insti-
tute of the Agricul-
tural Research Coun-
cil in Stellenbosch,
South Africa.
Methyl bromide is
critical to agriculture Technician Brian
worldwide as a soil essential oils for pi
fumigant, postharvest antifungal soil fun
storage protectant,
and quarantine treat-
ment to control many pests on various
crops. The primary use for this chemical
is to fumigate soil to destroy soilborne
pests. However, the escape of some of
the fumigant from the soil into the atmos-
phere has led to its being declared an
ozone depletor. So, under the U.S. Clean
Air Act, production and importation of
methyl bromide will be banned in the


United States in 2005.
"For several years now, we've been
diligently searching for practical and ef-
fective alternatives to methyl bromide,"
says ARS administrator Floyd P. Horn.
"This fumigant is used on more than 100
crops. And differences in soil types,
weather, importing country requirements,
and many other factors complicate the
"Our collaboration with industry, uni-
versities, state agencies, and internation-
al organizations is vitally important to
our search," Horn says. "This joint work
with Israel and South Africa could lead
not only to viable alternatives to methyl
bromide, but to
jointly patented
commercial prod-
ucts as well."
In lab studies at
Wilson and col-
several natural
plant volatiles that
have fungicidal
"We protected
fruit against post-
harvest decay with
these compounds,"
says Wilson. "We
found one-benz-
aldehyde-to be
particularly effec-
tive. Then we went
o evaluates plant a step further and
ntial use as used benzaldehyde
nts. to fumigate soil and
found it very effec-
tive against sever-
al soil pathogens."
This work is collaborative with Deb-
orah R. Fravel, a plant pathologist with
the ARS Biocontrol of Plant Diseases
Laboratory in Beltsville, Maryland. Wil-
son and another associate, Jose Solar,
have applied for a patent on a time-
release formula of benzaldehyde to fu-
migate fruit, grain, and soil.

"Since it is inexpensive, easily bio-
degradable, and breaks down into pro-
ducts that aren't harmful to humans,
animals, or the environment, benzalde-
hyde would be a desirable alternative to
methyl bromide as a soil fumigant,"
Wilson says.
He and Fravel found that soil fumi-
gated with benzaldehyde initially had
significantly lower pH values. However,
within 2 weeks, the pH returned to pre-
vious, nonfumigated, levels. Says Wilson,
"This showed that the changes in soil pH
are readily reversed and should not inter-
fere with crop production."
Wilson and colleagues have found
several natural plant volatiles that are
effective against soilborne pathogens
such as Fusarium oxysporum, Rhizocto-
nia solani, Pythium aphanidermatum,
and Sclerotinia minor.
To find potential alternatives to meth-
yl bromide, more research is needed on
the destructive, or biocidal, activity of
natural plant compounds against a wide
range of pathogens, insects, and weeds.

A Quick, Easy Test for Fumigants
In addition to comparing the efficacy
of natural fumigants in different soil types
and different applications, scientists will
need to evaluate delivery systems, Wil-
son says.
"The first order of business is to find,
in the lab, the compound or combination
of compounds that will control soilborne
pests and diseases," he explains. "Then,
we'll need to test these in soil and even-
tually begin field tests to complete the
research. We already have several inter-
ested companies."
It is difficult to evaluate the effec-
tiveness of fumigants on soil in planting
beds or greenhouse containers.
To test a fumigant's effectiveness,
large volumes of soil must be fumigated,
and elaborate evaluation procedures need
to be devised. With the help of Fravel,
Wilson built an apparatus to quickly and
easily test soil fumigants against soil

Agricultural Research/March 1999

"Simple to use, this equipment allows
the soil to retain uniform amounts of a
fumigant for a definite period. Once the
soil is fumigated, it can be tested for
pathogen activity," Wilson reports.
Wilson and Fravel successfully used
it to evaluate the effectiveness of benzal-
dehyde and nitrogen against soil patho-

Partnering Up To Find Alternatives
Eli Shaaya, who is with the Depart-
ment of Stored Products at the Volcani
Center, works closely with Wilson on the
search for natural compounds that might
replace methyl bromide.
He and colleagues have identified sev-
eral essential oils extracted from herb
and spice plants that have proven effec-
tive as fumigants. They have used these
extracts to control the most common
stored-product insects-the rice weevil,
lesser grain borer, sawtoothed grain bee-
tle, and red flour beetle.
Shaaya also found that several of the
essential oils were active against cut-
flower insects, including the whitefly.
Wilson has also been working with
Johan Combrink of INFRUTEC. Essen-
tial oils from indigenous South African
plants are now being marketed as flavor
and fragrance compounds.
"These oils could also provide a rich
source of new compounds that may fu-
migate soil, agricultural commodities,
and physical structures," Wilson says.
Combrink and colleagues are seeking
natural plant compounds that fight Bo-
trytis cinerea, Penicillium expansum,
Mucor piriformis, and Rhizopus nigri-
cans-pathogens that attack pome fruit,
such as apples. They are now controlled
with chemicals.
When the research project gets in full
swing in South Africa, Combrink and
colleagues plan to test natural compounds
on controlling weevils, the dried fruit
moth, and mites on dried fruit. They'll
also investigate controlling the root-knot
nematode-a worldwide pest and one of
the most significant nematode pests-on

a wide range of crops, including stone
fruits and vegetables. They will also test
natural compounds on the ring nematode,
a serious pest of stone fruit and peach
orchards not only in South Africa, but in
Georgia and South Carolina as well.
In addition, they will fumigate with
new natural compounds to control Fusar-
ium wilt on melons, root rot on strawber-
ries, Phytophthora root rot on citrus,
replant syndrome on apples, clubroot on
cabbage, and damping-off on vegetable
Two South African companies, Uli-
mocor and the Ciskei Agricultural Cor-
poration, are interested in this research,

tives to this heavily relied-on chemical.
The new legislation ensures that regula-
tions governing U.S. use, production,
import, or export of methyl bromide are
no more stringent or restrictive than those
required by the Montreal Protocol. In-
stead of the earlier January 1, 2001, tar-
get cutoff date, U.S. growers may now
use methyl bromide until 2005.
"This reprieve makes our research
even more critical," Wilson says. "It gives
us a little more time to find and test more
natural compounds that may replace
methyl bromide."-By Doris Stanley
Lowe, ARS.
This research is part of Methyl Bro-

Plant pathologist Charles Wilson transfers soil fumigated with natural plant volatiles into a
beaker for examination.

as is the Maktishim Chemical Company
in Israel. Wilson has also been talking
with a couple of U.S. companies about
research results.

A Reprieve for Methyl Bromide
Legislation passed with the FY 1999
Agriculture Appropriations Bill delays
the ban on methyl bromide because U.S.
growers have very few viable alterna-

mide Alternatives, an ARS National Pro-
gram described on the World Wide Web
Charles L. Wilson is at the USDA-
ARS Appalachian Fruit Research Sta-
tion, 45 Wiltshire Rd., Kearneysville, WV
25430-9425; phone (304) 725-3451,
X330, fax (304) 728-2340, e-mail *

Agricultural Research/March 1999

In cooperation with University of California scientists and others, ARS plant pathologist
Lars Anderson researches treatments that will stem the growth of aquatic weeds such as
Eurasian watermilfoil.

asian watermilfoil-and its ras-
cally cousin parrotfeather-can
quickly take over lakes, rivers,
irrigation canals, farm ponds,
and other watery habitats. They crowd
out desirable native vegetation, clog irri-
gation systems, and make waterways un-
suitable or unpleasant for boating, fishing,
and swimming.
Native to Europe and Asia, Eurasian
watermilfoil, Myriophyllum spicatum,
has been found throughout the United
States. Parrotfeather, Myriophyllum

aquaticum, an escaped South American
species, is less pervasive in the United
States than Eurasian watermilfoil. How-
ever, parrotfeather forms denser stands
that make ideal breeding grounds for
At Davis, California, ARS plant phys-
iologist Lars W.J. Anderson and col-
leagues in the agency's Exotic and
Invasive Weed Research Unit are seek-
ing new ways to control the two weeds.
Working with scientists at the University
of California, Davis, they've shown for
the first time that a widely used aquatic

herbicide-applied to above-water shoots
of parrotfeather-may appear effective
at first, but does little to knock out the
extensive underwater growth of the weed.
A better tactic for the future may be to
apply the herbicide triclopyr below the
water surface. The ARS scientists were
the first to test this chemical on parrot-
feather. They conducted the experiment
at a 20-acre lake in the oak woodlands of
Beale Air Force Base in northern Cali-
fornia. The lake has been infested with
this weed for about 20 years.
Anderson did the work under terms of
an experimental use permit from the U.S.
Environmental Protection Agency. He
collaborated with resource managers at
the base and with Dow AgroSciences
LLC, which markets the herbicide as
Garlon 3A for use in other ecosystems.
So far, according to Anderson, triclopyr
worked better than any other option test-
ed at the lake.
Anderson and co-researchers are also
conducting sophisticated laboratory anal-
yses of the two milfoils to precisely iden-
tify differences in the genetic makeup of
these weeds from different sites. That
approach could boost the success of bio-
logical control insects such as the water-
milfoil weevil, Euhrychiopsis lecontei.
For best results, weevils recruited to
stop the spread of the weeds should be
matched as closely as possible to Eur-
asian watermilfoil plants most genetical-
ly similar to those from which the insect
was collected. University scientists in
Vermont and Minnesota have already
conducted some biological control tests
with this little brownish-black insect.
Other ARS investigations have re-
vealed differences in the chemical make-
up of Eurasian watermilfoil. Those
differences might affect the plant's nu-
tritional value to the weevil-and thus
the weevil's vigor, according to ARS
ecologist David F. Spencer at Davis.
Nitrogen in Eurasian watermilfoil plants
sampled from the Truckee River in Cal-
ifornia, for instance, was "lower than the
nitrogen content in plants sampled from

Agricultural Research/March 1999

a shallow research
pond at the Davis
lab," says Spencer.
"Studies done by
ARS scientists in
Florida," he notes,
"showed that the rel-
ative growth rate of
a weevil that eats a
water weed called
hydrilla increased
by 50 percent when
the weevil was fed Eurasian watermilfoil, Myriophyllum
plant material with spicatum, at flowering stage.
3.5 percent nitro-
gen, as compared to
plant material with only 2 percent nitrogen."
Based on those results, differences in nitrogen in Eurasian
watermilfoil plants from various sites might also make a
difference in how fast the helpful weevils develop-and how
effectively they foil these notorious weeds.-By Marcia
Wood, ARS.
This research is part of Crop and Commodity Pest Biology,
Control, and Quarantine, an ARS National Program de-
scribedon the World Wide Web at http://www.nps.ars.
Lars W.J. Anderson and David F. Spencer are in the USDA-
ARS Exotic and Invasive Weed Research Unit, c/o UC Davis,
One Shields Ave., Davis, CA 95616; phone (530) 752-6260
[Anderson], (530) 752-1096 [Spencer)], fax (530) 752-4604,
e-mail *
Plant physiologist
Lars Anderson
checks water-
milfoil for shoot

Vaccinating Hens at the Right Time
Saves Eggs

Vaccinating laying hens for a respiratory disease at the
right time can save several eggs per hen each year.
Mycoplasmosis, a serious respiratory disease of poultry, is
caused by tiny bacteria that infect about 80 percent of all
laying hens. Unvaccinated hens average 15 fewer eggs per
In 1981, research by USDA's Agricultural Research Ser-
vice and Animal and Plant Health Inspection Service, the
University of Georgia, and a group from the egg industry
showed that vaccinating laying hens at about 18 weeks of age
with the F strain of Mycoplasma gallisepticum controlled the
The problem was that vaccinating hens while they were
laying lowered egg production by seven eggs per hen per year.
Now, new ARS research shows that the timing of vaccina-
tion-before hens begin laying-enables them to maintain
full egg production, or about 253 per year.
"The corrected timing amounts to an $82 million a year
increase in production for the U.S. egg industry, which now
averages annual sales of about $3.8 billion," says veterinarian
Scott L. Branton. He is in the ARS Poultry Research Unit at
Mississippi State, Mississippi.
For their latest research, the ARS scientists used laying
hens that did not have the disease. They say that egg producers
can now administer the currently available vaccine before the
hens begin laying, without worrying about lower production.
Branton and an ARS colleague, physiologist James D.
May, are presently working on a new genetically engineered
form of the vaccine that could be used to inoculate eggs. It will
use a gene from the F strain of the bacteria inserted into a
genetically engineered form of the vaccine. The researchers
say they are about 8 years away from reaching this goal.
They believe the new vaccine will have another advantage:
It will pose no harm to broilers or turkeys. The currently
available vaccines have limitations-they can be pathogenic
to broilers and turkeys or provide only limited protection from
the bacteria.-By Hank Becker, ARS.
This research is part of Animal Health, an ARS National
Program described on the World Wide Web at http://
Scott L. Branton and James D. May are in the USDA-ARS
Poultry Research Unit, P.O. Box 5357, Mississippi State, MS,
39762; phone (601) 323-2230, fax (601) 323-3535, e-mail *

Agricultural Research/March 1999


A Kamal Bunt Fungus Look-Alike

S sometimes distinguishing the
real thing from an impostor
takes a lot of expertise and
know-how. This is especially
true with microscopic organ-
isms such as Tilletia indica, a fungus that
causes the disease called Karnal bunt in
But Agricultural Research Service
fungus-identifying experts have made
this difficult task look easy.
Working with state and federal re-
searchers, they've developed a technique
to unmask a ryegrass fungus that was
mistakenly identified as a possible form
of Karnal bunt. In so doing, they've helped
solve a serious problem affecting U.S.
farmers and disrupting international trade.
Southeastern wheat growers should now
face less risk of a regulatory action on
their wheat crop due to Karnal bunt.
In 1996 and 1997, much of the $5-
billion-a-year U.S. wheat export market
was threatened by the discovery of the
real Karnal bunt in Arizona and a small
part of California.
"About one-third of the foreign
countries that might buy wheat from the
United States will not buy Karnal-bunt-
infected wheat," says Mary E. Palm, a
mycologist with USDA's Animal and
Plant Health Inspection Service (APHIS).

Palm' sjob as a federal quarantine official
is to identify suspicious or unknown fungi
intercepted at ports of entry into the
United States. Because of the possibility
that the disease was widespread, the
export of all U.S. wheat was threatened,
she says.
"Karnal bunt is a disease that is quar-
antined around the world-meaning
many countries that don't have the fun-
gus won't buy wheat from countries
where it is found. So keeping the disease
out of American wheat has been a top
priority," she adds.
In making plant quarantine decisions,
it is essential that fungi be identified
accurately. This not only keeps out non-
indigenous pathogenic fungi, but also
allows the entry of food and fibers infect-
ed by fungi that are already present in the
United States and, thus, are not a plant
quarantine concern.
"Throughout the U.S. national Karnal
bunt survey during the summer of 1996,
T. indica-like fungal spores, or
teliospores, were found in wheat seed
washes of grain from the southeastern
United States," Palm says. "Although
available tests indicated these samples
tested positive for Karnal bunt, we found
no bunted-that is, blackened and foul-
smelling-wheat seeds, which would

indicate the presence of the disease, in
any of the samples from which these
teliospores were found."
Palm explains, "Sometimes, ryegrass
seed infected with a fungus gets harvest-
ed along with the wheat. Initially, avail-
able tests have incorrectly identified this
fungus as Karnal bunt. As a result, in
1996 and early 1997, restrictions were
placed on the movement of suspect wheat
from Alabama, Georgia, Florida, and
Working with Palm at the ARS Sys-
tematic Botany and Mycology Laborato-
ry in Beltsville, Maryland, mycologist
Lisa A. Castlebury set about to solve the
mystery of the bunt fungus.
Even though wheat seed wash sam-
ples were testing positive for the Karnal
bunt fungus using the then-available
molecular test, Castlebury and Palm were
detecting structural, or morphological,
differences. Because no bunted wheat
kernels were found in the southeastern
United States, they suspected the pres-
ence of an impostor masking as the de-
structive fungus.
At present, about 1,200 species of
bunts are known worldwide," says Cas-
tlebury, whose specialty is bunt and smut
fungi. "They occur worldwide and infect
about 4,000 plant species in more than 75

Agricultural Research/March 1999

Wheat in-
fected with
Tilletia indica.

flowering plant families. They cause
millions of dollars in losses to both food
crops and ornamental plants."
Castlebury used the basic tools of sys-
tematics to study the unknown and un-
named ryegrass fungus. After close
examination of the bunt fungi family, she
determined the Tilletia species was an
unnamed fungus new to science.
Castlebury analyzed and character-
ized the teliospores of both dried and
fresh specimens. After noting their shape,
size, surface characteristics, and color,
she found that light and scanning elec-
tron microscopy could be used to further
examine and compare the two fungi. With
these techniques, she determined that
visual characteristics can be used to tell
the two fungi apart.
"Mature T. indica teliospores on wheat
appear dark red-brown, often opaque,
with fine spines that densely cover the
outer spore coat. The teliospores on
ryegrass range in color from pale yellow
or golden to dark brown, with thicker,
more widely spaced spines covering the
outer coat," says Castlebury.
She validated her technique by rigor-
ously comparing previously observed
differences in spore ornamentation in
samples from known host plants.
The technique quickly showed that
100 percent of each of the 70 wheat
samples collected from southeastern
farms in 1996 were contaminated with
the look-alike fungus-not Karal bunt.
"As a result, in March 1997, restric-
tions on the movement of the suspect
wheat were lifted from the counties where
the suspect samples originated," says
Palm, who used Castlebury's test.
Palm and other federal plant quaran-
tine officials now use the technique as a
first cut, to decide if possible quarantine
actions are needed. "If the test results
indicate a sample might be Karnal bunt,
officials go back and look for bunted
wheat seeds," says Palm.
Castlebury and plant pathologist Lori
M. Carris at Washington State Universi-
ty in Pullman have described the new

species and
named it Til-
letia walk-
eri. Their
paper will
be pub-
lished in My-
cologia-the official
journal ofmycologists world-
Carris is also working on several
greenhouse experiments at Pullman to
see if the ryegrass fungus is able to infect
other grass hosts under artificial condi-
"We may find, as with other Tilletia
species, that it could infect species other
than ryegrass in the greenhouse," says
Carris, "But in nature, these fungi are
generally host specific."

A scanning electron micograph of a ryegrass
bunt spore from Tennessee (top) displays
thicker, wider ridges and grooves than those
of a Karnal bunt spore (bottom). Magnified
about 2,000x.

bury and
Carries also
%% worked with
\ PHIS mycol-
ogist Robert J.
IS pl.atl patholo-
glet Laurene Levy
at the USDA Na-
tional Plant Germ-
plasm Quarantine Center in Beltsville.
They have developed a new molecu-
lar test that will be the definitive one for
official use to tell the two fungi apart. It
uses a standard restriction enzyme anal-
ysis to distinguish between the two.
"Our test uses a set of PCR [poly-
merase chain reaction] primers to ampli-
fy specific genes from the mycelium or
fungal tissue of the suspect fungi. We
have a restriction enzyme that cuts the
amplified ryegrass fungus gene, but not
the Karnal bunt fungus gene, into two
pieces," says Levy.
"We've tested it using nine other Tille-
tia species on grasses."
Two other labs that routinely perform
molecular tests-at Frederick, Maryland,
and Pullman, Washington-have vali-
dated the accuracy of Levy' s PCR test.-
By Hank Becker, ARS.
This research is part of Plant Diseas-
es, an ARS National Program described
on the World Wide Web at http://
Lisa A. Castlebury and Mary E. Palm
are at the USDA-ARS Systematic Botany
and Mycology Laboratory, Bldg. 011A,
10300 Baltimore Ave., Beltsville, MD
20705; phone (301) 504-5364 or (301)
504-5327, fax (301) 504-5810, e-mail
lisa @
maryp @ nt.
An interactive system for identifying
teliospores of species of Tilletia that oc-
cur in the United States is now available
through the Systematic Botany and My-
cology Laboratory's web site. Go to http:/
/ *

Agricultural Research/March 1999

Delta MSEA

N ature holds many surprises, but
trained ecologist Ben Cash
never expected to see turtles
eating cotton.
No one is sure why a quarter
of the turtles studied had cotton in their
feces. Normally, sliders-the water-
dwelling turtles that Cash, a graduate
student at the University of Mississippi,
was studying-prefer algae. Cash was
monitoring the health of the turtles for a
doctoral research project.
"Though the sliders favor algae, these
specimens seemed to be opportunistic
feeders," Cash says. "Beavers could have
dragged the cotton and soybeans into the
lake, or egg-laying females could have
had them as an on-land snack. But the
feeding behavior might also be a reflec-
tion of the ecosystem's health. That's
why we were looking at it," he says.
However, Cash wasn't just studying
turtles' food habits; he was mainly draw-
ing blood samples. And his work was
only a small part of research going on at
Deep Hollow Lake near the Yazoo Riv-
er, northwest of Jackson, Mississippi.
The theory is that slider turtles, which
may live up to 45 or 50 years, can provide
both short-term and long-term indica-
tions of an ecosystem's health. The con-
cept is that levels of the stress hormone
corticosterone could be a monitoring tool.
Based on the blood samples, Cash saw no
evidence of slider stress, however.
Cash next intends to study other as-
pects of sliders-such as reproduction,
size, and population levels-and what
they show about the lake ecosystem.
Agricultural Research Service ecol-
ogist Scott S. Knight gave Cash the op-
portunity to work on Deep Hollow Lake
as part of his doctoral research. Knight,
who is in the ARS Water Quality/Eco-
logical Processes Research Unit at
Oxford, Mississippi, was looking at con-
ditions and changes at Deep Hollow, 7
including the fish population.
"We saw signs of stress-particularly 0
in the sunfish populations," says Knight.
"The fish were small, and many were -

It's Just One Facet of the Big MSEA Picture

diseased. We also saw some hybridiza-
tion where different species were inter-
Why is Deep Hollow, a 20-hectare
(50-acre) oxbow lake that stands between
Sunflower and Leflore Counties in Mis-
sissippi, getting all this attention?
It's a test lake for a Management Sys-
tems Evaluation Area (MSEA), a nation-
al effort by the U.S. Department of Agri-
culture to protect farmlands' watersheds.
When work began on Deep Hollow
Lake in 1995, water visibility was at 4
centimeters (1.6 inches), and there
were few plants or algae. Today, BOE
depending on the time of year, visi-
bility runs 35 to50 centimeters (14 to
20 inches), and the algae the slider
turtles love to eat are coming back.
The MSEA program is designed
to test and develop farming methods
that will work with nature, instead of
damaging water quality. It began in
the Midwest in 1990.
Oxbow lakes are created when a
river cuts a new path across a large
bend, usually during flooding, and
isolates a u-shaped section of the
river. Oxbows make perfect ecology
laboratories because they are essen-
tially closed ecosystems. A!
In this project there are three lakes: M
Deep Hollow, Beasley, and Thigh- G
man. Each lake represents different
kinds of farm management practices
and how they affect water ecosystems.
Phillip Barbour farms cotton and soy-
beans on the land around Deep Hollow
Lake. He agreed to help the research
teams by using best management prac-
tices on the land. That committed him to
using not only cutting-edge erosion con-
trols, but also the latest in pollution
reduction techniques. Meanwhile, the
farmer at Beasley Lake uses structural
erosion barriers and the one near
Thighman Lake, traditional farming
practices. Both serve as comparisons.
"If farmers find that best management
practices make economic sense and don't
take too much extra effort, that will help

ensure they're adopted," says Knight.
"It's funny. Even the control lake is get-
ting better. That's because more farmers
are seeing the value of improved erosion
control and are doing it for themselves."
Implementing best management prac-
tices has meant lots of work for Barbour.
He planted no-till cotton and soybeans.
Tilling loosens the soil, allowing more
air to get to plants' roots, but it can
contribute to erosion. So Barbour also
planted a crop in winter to protect the soil
from harsh winds and rain. ARS research-

SNICHOLS (K8320-9)

IS ecologist Scott Knight (left) and University of
ississippi graduate student Ben Cash observe a red-
red slider turtle taken from Deep Hollow Lake near
greenwood, Mississippi.

ers helped him set pipes in the soil to
drain water away without having it run
over land, tearing away valuable topsoil.
And he planted riparian zones, a system
of ditches and strong plants designed to
trap soil runoff.
Barbour also worked with ARS re-
searchers in Stoneville, Mississippi, on
weed sensor technology that allows him
to use pesticides with precision. This
method shows him exactly where weeds
are, so he doesn't have to apply herbicide
throughout his fields.
These techniques don't stop erosion,
but they do reduce the amount of herbi-
cide going into Deep Hollow or other

ecosystems. And they could save money,
since Barbour doesn't have to spend as
much on agricultural chemicals.
The good things happening at Deep
Hollow are just one of MSEA's success
stories. There are MSEA projects in oth-
er parts of the United States, including
Ohio, Minnesota, and Nebraska. Many
ARS research locations are committed,
through MESA and other projects, to
finding new, environmentally sound farm
management practices.
The Mississippi Delta MSEA was the
first located in the South and the first
to investigate ecological benefits be-
yond changes to water quality. It
looks at the entire ecosystem. That's
why Ben Cash's turtle project was
part of this effort.
Scientists with ARS, the U.S.
Geological Survey, and Mississippi
State University lead the project.
Other conservation groups, such
as Ducks Unlimited, and farm sup-
pliers have also become MSEA sup-
porters in the Delta. And the Missis-
sippi Delta MSEA has enjoyed the
endorsement of such agricultural
support organizations as the Farm
Bureau, Delta Council, and Missis-
sippi Soil and Water Conservation
The Delta Branch Experiment
Station, Natural Resources Conser-
vation Service, Mississippi State
University, University of Mississippi, and
the state's Departments of Environmen-
tal Quality and Wildlife Fisheries and
Parks are also involved.-By Jill Lee,
This research is part of Water Quality
and Management, an ARS National Pro-
gram described on the World Wide Web
Scott S. Knight is in the USDA-ARS
Water Quality/Ecological Processes Re-
search Unit, 598 McElroy Dr., Oxford,
MS 38655; phone (601) 232-2935, fax
(601) 232-2915, e-mail knight@sedlab. *

Agricultural Research/March 1999


Cytologist William Wergin (left) and zoologist David Chitwood focus on Caenorhabditis elegans, a free-living nematode species that is
serving as a model for studying the biochemistry of soybean cyst and root-knot nematodes.



fo Cotl


year reprieve on the Jan. 1,2001,
phaseout date for methyl bro-
mide, researchers at the ARS
Nematology Laboratory in
Beltsville, Maryland, are searching for
replacements to control microscopic
worms called plant-parasitic nematodes.
Thousands of species of these worms
infect nearly every agronomic and horti-
cultural plant important to agriculture. In
the United States, these pests cause esti-
mated annual economic losses of $9 bil-
lion from decreased food, fiber, and
ornamental production. Although used
to protect more than 100 crops from
nematodes and a variety of other pests
and pathogens, methyl bromide will be
prohibited as of January 1, 2005.
"According to the U.S. Environmen-
tal Protection Agency, 35 percent of the
world's methyl bromide production is
used by U.S. agriculture," says ARS zo-

ologist David J. Chitwood. "Eighty-sev-
en percent of this is used for preplant soil
fumigation to kill soilborne fungi, as
well as nematodes.
"At the present time, only a small
array of chemicals-which are frequent-
ly inadequate, unsuitable, or too costly
for some crops or soils-are available to
control these pests," he says. "When
methyl bromide goes, there will only be
two broad-spectrum fumigant nemati-
cides left, and one of them is in danger of
being restricted."
Chitwood says there's an urgent need
to develop environmentally safe, target-
specific ways of controlling soybean cyst
and root-knot nematodes, two of the worst
soil-dwelling pests. The first attacks soy-
beans; the second feeds on strawberries,
most vegetables, and just about all other
agricultural crops. These pests feed on
the living roots of plants, weakening and
sometimes killing their host.

Agricultural Research/March 1999

Chitwood's lab is the only ARS re-
search group devoted exclusively to
studying nematodes. It's a hub for find-
ing state-of-the-art control techniques.
Several of the labs' research projects
have produced some promising results in
the ongoing battle to keep these pests in

An Elegant Genetic Approach
One project involves what are called
free-living nematodes. These cousins of
plant parasites are important in nutrient
recycling within soils.
"Several scientists at the lab are study-
ing one free-living species-Caenorhab-
ditis elegans. It can be used as a model
organism to explore the biochemistry of
its two destructive cousins, the soybean
cyst and root-knot nematodes," Chitwood
For example, the C. elegans genome
sequencing project has just yielded the
genetic pattern of that organism-the
complete structure of the genetic materi-
al, or DNA, that makes it unique. This is
the first multicellular animal for which
such valuable information is available.
This project, he says, will give ARS
plant pathologists and molecular biolo-
gists a very powerful way to speed up the
identification of genes that control plant-
parasitic nematode growth, development,
and sex determination.
"Since the ability to sense and re-
spond appropriately to environmental
cues is critical for all nematodes," says
ARS molecular biologist Andrea M.
Skantar, "it is likely that plant-parasitic
ones use a mechanism similar to that of
free-living relatives to adapt to changes
in their environment and know when to
mature and reproduce."
To that end, Skantar and colleagues
are studying one of the most critical
junctures in the life cycle of many plant-
parasitic nematodes-the pre-infective
larval stage. At this vulnerable stage, she
explains, the parasite's development is
on hold until it finds a suitable plant host
in which to mature and reproduce.

Skantar hopes to exploit this vulnera-
bility, either by preventing maturity alto-
gether or by tricking the worm into
developing prematurely outside the host
plant-where it would likely starve to
"Plant-parasitic worm larvae share a
number of traits with their free-living C.
elegans relatives," she says. During the
arrested state, the worms don't feed; their
outer shell, or cuticle, becomes stress-
resistant; their bodies adapt for energy
storage verses energy production; and
they live longer.

Going a Little Daffy
"In C. elegans, these changes are
mediated by molecules called the daf
genes. Environmental cues and insulin-
like signals all pass through this dafsen-
sory processing pathway that enables
these nematodes to couple their food
uptake with development and lifespan,"
says Skantar.
She used a process called PCR ampli-
fication to find dafgenes in soybean cyst
and root-knot nematode DNA.
In PCR, or polymerase chain reaction,
a heat-stable enzyme uses
molecules called primers as
'bait' to isolate and make
copies of a target gene from
the organism's DNA.
Skantar is developing
procedures to micro-inject
nematodes with normal or
altered copies of these
cloned genes. By examining
the effects of this injection
on nematode development,
she hopes to understand how
parasitic nematodes differ
from free-living ones.
"A thorough molecular
understanding of how a
nematode responds to envi-
ronmental stimuli by alter-
ing its development will A scanning
uncover novel targets for biologist An
the ovary of
controlling nematodes," she marker gen
says. provide clue

Skantar believes the dafgenes may be
used to permanently disrupt these pests'
development so they remain as nonfeed-
ing larvae for an entire crop-growing
season. After that, they would perish.
Searching for other new management
schemes for nematodes, ARS plant pa-
thologist Susan L.F. Meyer and ARS
chemist James Nitao are looking at var-
ious beneficial fungi and at phero-
mones-male and female sex attractants.
Meyer and colleagues collected 250
fungi from soybean-growing areas of
China, where soybeans were first culti-
vated, to look for natural biological con-
trols. She and Nitao screened most of
these fungi in the lab to see if they inhibit
egg hatch in plant parasitic nematodes.
"Fifteen of the fungi isolated from
soybean cyst nematode eggs produce
compounds that reduced egg hatch of
either soybean cyst nematodes or root-
knot nematodes by at least 80 percent,"
says Meyer, "and one isolate reduced
hatch of both nematodes. Compounds
from three of these isolates also caused
the root-knot nematode larvae that did
hatch to stop moving."

electron microscope guides molecular
drea Skantar in injecting an altered gene into
an adult C. elegans nematode. A fluorescent
e will tag the transformed offspring and
s about gene function inside the worm.

Agricultural Research/March 1999

Bacterial-feeding nematodes, Operculorhabditis sp. LKC10, frozen
in liquid nitrogen. Magnified about 30x.

Nitao has analyzed these secretions and is isolating the
compounds that inhibit hatching. Next, he will test these com-
pounds in the greenhouse to determine their commercial control
In another approach, Chitwood and other ARS scientists are
trying to develop new control methods for parasitic nematodes
by studying their biochemistry and that of their host plants.
Chitwood is an expert on the biochemistry of the steroids and
fats, or lipids, of nematodes. Steroids are important components
of nematode membranes and biochemical precursors of their
hormones. Lipids are used as food reserves and as communica-
tion molecules between and within their cells. Chitwood is
working on methods of disrupting the nematode's life cycle by
interfering with its steroid and fat biochemistry.
One of the most unusual tactics for attacking nematodes is
that of ARS cytologist William P. Wergin. He wants to kill the
nematodes using dry ice, which is solid carbon dioxide that has
a temperature below -78.50C. A nonpolluting material, the dry
ice can be applied to the soil before planting to lower soil
temperature enough to either kill nematodes or reduce their
infection and reproduction on plants.
"Results indicate that this treatment reduced by several
hundredfold the number of nematode eggs that could be found
on mature plant roots," says Wergin. "Although further studies
are needed to optimize and economize this procedure, the dry
ice treatment may provide some farmers with an environmental-
ly safe and effective means to control certain types of these plant
parasites."-By Hank Becker, ARS.
This research ispart ofMethyl Bromide Alternatives, anARS
National Program described on the World Wide Web at
Scientists mentioned in this story can be reached at the
USDA-ARS Nematology Laboratory, Bldg. 011A, 10300 Balti-
more Ave, Beltsville, MD 20705-2350; phone (301) 504-5660,
fax (301) 504-5589, e-mail
smeyer *

Moms' Low Copper

Could Harm Newborns

Researchers at ARS' Grand Forks Human Nutrition Re-
search Center think they have unearthed a link between copper
deficiency during pregnancy and neurological defects it causes
in the offspring of laboratory animals. Their findings may have
implications for people in industrialized nations, says Tom
Johnson, who heads cell membrane biochemistry research at
the North Dakota center.
An inherited disorder that leads to low copper concentra-
tions in infants' brains severely retards neurological develop-
ment. While U.S. and other western-type diets contain enough
copper to prevent such a serious deficiency, he says, their
copper level is still less than desirable. That's because oysters,
liver, and whole grains-foods that are not mainstays in the
U.S. diet-are among the best sources of copper.
"We don't know how consumption of relatively low-cop-
per, western diets during pregnancy and nursing affects brain
development in infants," says Johnson.
The brain has several copper-containing enzymes that would
suffer from a shortage of copper, he says. Copper deficiency
also reduces the activity of several enzymes that don't contain
copper. One of those enzymes is protein kinase C (PKC), as
Johnson discovered in earlier experiments with blood plate-
lets. Three forms of PKC show up in the brain just after birth
and are involved in development of the nervous system.
So Johnson and his assistants Anne Thomas and Amy
Lozano looked at PKC levels in the brains of rat pups whose
mothers were fed diets lacking adequate copper throughout
pregnancy and for a few weeks after delivery. One group got
only 1 microgram (mcg) of copper per gram of diet daily-one-
sixth the level recommended for pregnant rats. The second
group got 2 mcg per gram of diet, or one-third the recommend-
ed level. And a control group got all the copper they needed.
All three forms of PKC increased in all the pups' brains
during the 3 weeks after birth, says Johnson. But the increase
was half as much in the group whose moms got only 1 mcg of
copper per gram of diet.
"We saw a 25 percent drop, even at 2 mcg," he adds, noting
that one form of PKC was off by 50 percent in the cerebellum-
the part of the brain that controls motor function. That's
significant, says Johnson, because a well-known symptom of
copper deficiency in baby animals is poor muscle coordina-
tion. "These changes in PKC expression occur during a period
of increasing complexity in the central nervous system."
The lesson for human mothers is that an adequate copper
intake during pregnancy may be critical. The Reference Daily
Intake (RDI) is 2 milligrams.-By Judy McBride, ARS.
W. Thomas Johnson is at the USDA-ARS Grand Forks
Human Nutrition Research Center, P.O. Box 9034, University
Station, Grand Forks, ND 58202-9034; phone (701) 795-
8411, fax (701) 795-8395, e-mail tjohnson@gfhnrc.ars.usda.
gov. *

Agricultural Research/March 1999

A Snapshot of Blood

Homocysteine Levels

Cholesterol isn't the only blood
component associated with the
risk of heart disease and stroke.
Since the early 1990s, the ami-
no acid homocysteine-a by-
product of amino acid metabolism-has
emerged as another important risk fac-
Researchers believe that when body
cells dump too much homocysteine into
the blood, artery linings become irritat-
ed, encouraging the formation of
plaque-fatty deposits that cling to ar-
tery walls.
One cause of this dumping is a low
intake of folate, vitamin B6, or vitamin
B12, according to earlier findings by
researchers at the Jean Mayer USDA
Human Nutrition Research Center on
Aging at Tufts University in Bos-
ton, Massachusetts. Body cells
need these three B vitamins
to convert the amino acid
methionine to cysteine. In
When any one is lacking,
the intermediate product ci
in the conversion, homo-
cysteine, builds up.
In 1993, the Boston
researchers were first to re-
port homocysteine levels in any popu-
lation-more than 1,100 elderly in the
original Framingham (Massachusetts)
Heart Study. Even in this relatively nar-
row age range-67 to 96 years-ho-
mocysteine levels increased with age.
Men had higher levels than women, but
the difference narrowed at the upper ages.
Two years later, Norwegian research-
ers reported similar age and gender dif-
ferences among the middle-aged
population in their country. Smaller pop-
ulation samples in the United States and
Europe generally support these findings.
But the studies covered specific age
groups and were not representative of the
U.S. population as a whole.
"We wanted to describe serum ho-
mocysteine concentrations across our
population and test for differences among
sex, age, race, and ethnicity," says Paul

F. Jacques, an epidemiologist at the
USDA center involved in the earlier
In the current study, Jacques and his
Boston colleagues collaborated with sci-
entists affiliated with the Centers for
Disease Control and Prevention in At-
lanta, Georgia, and Hyattsville, Mary-
land. Using blood serum samples from
the latest National Health and Nutrition
Examination Survey, they measured ho-
mocysteine levels for 3,766 males and
4,819 females from age 12 up.
The results "confirm the age and sex
differences reported in nonrepresenta-
tive samples," says Jacques. Homocys-
teine levels increased with age. They
were also significantly higher in males

than females, regardless of whether the
subjects were white or black with no
Hispanic or Mexican-American back-
ground. Levels were closest between the
two genders in the young and old, di-
verging around puberty and converging
after menopause.
The researchers suspect that impaired
kidney function may contribute to the
higher levels in older people.
Body size, estrogen, and vitamin sta-
tus may explain the difference between
genders, they say. Larger people have
more creatinine-a protein breakdown
product-circulating in their blood. And
studies show a strong correlation be-
tween circulating creatinine and ho-
mocysteine levels. Also, "estrogen seems
to protect against high homocysteine,"
says Jacques,judging by the lower levels

in premenopausal women. Further, wom-
en are more conscious about nutrition.
The women in the study had a higher
folate status than the men.
Mexican-American females had the
study's lowest homocysteine levels-
significantly lower than non-Hispanic
black and white subjects. Jacques says
nutrition may explain part, but not all, of
the difference. He has not yet analyzed
the data to look for other factors.
"It's crucial we understand the basis
for these age and gender differences," he
adds, "because fairly modest increases in
homocysteine are strongly associated
with higher risk of vascular disease.-
By Judy McBride, ARS.
This research is part of Nutrient Re-
quirements, Food Composition, and In-
take, an ARS National Program
described on the World Wide
Web at http://www.nps.ars.
880- 107s2.htm.
Paul F. Jacques is at the
ie. Jean Mayer USDA Human
Nutrition Research Center
on Aging at Tufts University,
711 Washington St., Boston,
MA 02111; phone (617) 556-3322,
fax (617) 556-3344, e-mail *

Summaries of new ARSfindings
in nutrition, food safety, and
health are available in the Food
& Nutrition Briefs. This quar-
terly publication is available
electronically at http://
For a free subscription, contact
Judy McBride, nutrition editor,
at (301) 504-1628; or write to her
at 5601 Sunnyside Ave., Belts-
ville, MD 20705-5129; e-mail

Agricultural Research/March 1999

Trap Crops Prove

I rresitible

abbage, broccoli, collards,
kale, and other cole crops are
an all-you-can-eat salad bar
for diamondback moths, a pest named
for the diamond-shaped markings em-
bellishing its wings. Moth larvae, which
chew on plant leaves, take a big bite out
of cabbage and other crops worldwide,
costing billions of dollars in control costs
and losses.
Pesticide spraying can be costly, rang-
ing from about $10 to $21 an acre for
each application-depending on which
pesticides are used-and typically cost-
ing growers $80 to $168 per acre, or
more, each season to produce a crop. To
the farmer's dismay, diamondback moths
are becoming resistant to almost every-
thing, including Bacillus thuringiensis
(Bt)-based insecticides that are widely
used to kill certain pests while preserv-
ing beneficial insects.
Now entomologist Everett R. Mitch-
ell is taking another approach to spoiling
the moth's meal. He says giving the pest
a heaping serving of another vegetable-
collard greens-spoils its appetite for
cabbage. The moths can't resist the col-
lards when planted completely around
the edge of cabbage fields, a strategy
called trap cropping.
"Invading diamondback moths stop
and deposit their eggs on the collards,
rather than on adjacent cabbage plants,"
says Mitchell. "Diamondback popula-
tions continue to recycle in collards as
long as plants remain green and continue
to grow." Mitchell heads the Insect Be-
havior and Biocontrol Research Unit,
which is part of ARS' Center for Medi-
cal, Agricultural, and Veterinary Ento-
mology in Gainesville, Florida.
Mitchell recently conducted experi-
ments on nearby farms in northeast Flor-

ida that showed that the moths prefer to
feed on highly fertilized collard plants.
He tested this approach for more than 2
years. In all cases, he says, there was
minimal cabbage damage from diamond-
back moth larvae. The quantity and qual-
ity of cabbage produced equaled that
from conventionally sprayed fields.
This simple, low-tech, cost-effective
pest control method also reduced pesti-

back populations in check. The tiny D.
insulare wasp stings the larvae, prevent-
ing them from developing into adults and
laying more eggs. Once stung, a larva
becomes sluggish and stops feeding with-
in a few hours. The wasp doesn't attack
other insects or humans.
"We established that there needs to be
a threshold of 0.3 moth larva per plant
before a farmer has to apply pesticides,"
Mitchell says. "We found that even
though moth larval populations built up
in collards planted around field margins,
populations in cabbage generally re-
mained well below the threshold."-By
Tara Weaver, ARS.
This research is part of Crop and



Diamondback moth larvae feed on a cabbage leaf.

cide use. "Cabbage fields surrounded by
collards required 75 to 100 percent fewer
sprays to control diamondback moths
than fields treated conventionally with
pesticides. That's huge savings forfarm-
ers," notes Mitchell.
He also says Diadegma insulare, a
naturally occurring parasitoid that at-
tacks diamondbacks, builds in numbers
in the collards and helps keep diamond-

Commodity Pest Biology, Control, and
Quarantine, an ARS National Program
that can be viewed at http://www.nps.
Everett R. Mitchell is in the USDA-
ARS Behavior and Biocontrol Research
Unit, 1600 S.W. 23rd Dr., Gainesville,
FL 32604; phone (352) 374-5710, fax
(352) 374-5804, e-mail emitchell@ *

Agricultural Research/March 1999

to Diamondbacks


; :~

New Soft Wheat Fights
Powdery Mildew
A new breeding stock for soft red
winter wheat fought off all 10 strains of
powdery mildew tested against it in the
laboratory. Previously, fighting 8 of 10
was the best any wheat could do against
this fungal disease that costs growers $2
to $3 million a year and strikes worst at
soft red winter wheat. This type of
wheat-grown east of the Mississippi-
is made into flour commonly used by
bakeries to give cookies and cakes a
delicate texture.
Scientists at ARS, North Carolina State
University, and the University of Geor-
gia developed the new breeding stock,
named NC 97BGTAB-10. Its genes for
resisting powdery mildew come from
hardy, wild Middle Eastern ancestors of
modern wheat. Commercial seed com-
panies can use the new breeding stock to
build mildew resistance into their farm-
er-favored, bakery-bound soft red wheat
varieties. Steven Leath, USDA-ARS Plant
Science Research Unit, Raleigh, North
Carolina; phone (919) 515-6819, e-mail

Nature-Based Weapon
Against Salmonella Is a
Top Product of '98
Popular Science magazine named a
new commercial product from ARS re-
search as one of its "100 Best of What's
New for 1998." ARS scientists devel-
oped the product to reduce Salmonella
contamination in chickens. It was subse-
quently licensed by MS BioScience in
Madison, Wisconsin, and is sold as PRE-
EMPT. The product inhibits Salmonella
in chickens' intestines by introducing a
blend of 29 live, nonharmful bacteria
naturally present in healthy adult chick-
ens. The mix can be sprayed in a mist
over newly hatched chicks to give them
the same level of Salmonella resistance
that develops in an older bird.
In March 1998, the U.S. Food and

Drug Administration approved PRE-
EMPT for commercial use. This was the
first FDA approval of a bacterial mix as
a type of animal drug known as a compet-
itive exclusion product. PREEMPT can
help producers reduce Salmonella risks.
But proper food storage, handling, and
preparation remain essential to guard
against pathogens. An estimated 2 mil-
lion cases of Salmonella poisoning occur
in the United States each year. Most
exposure is from raw or undercooked
meat, poultry, milk, and eggs. Donald
Corrier, USDA-ARS Food Animal Pro-
tection Research Laboratory, 2881 F&B
Rd., College Station, TX 77845; phone
(409) 260-9484.

Baiting the Mexican
Fruit Fly
ARS scientists have designed a new
chemical lure for Mexican fruit flies,
important quarantine pests. Female Mex-
ican fruit flies lay eggs in at least 36
different fruits. Better lures and traps
will enable action agencies to detect-
and thwart-invasions sooner. The flies
periodically cross the Mexican border
and infest U.S. fruit orchards, most often
in the Lower Rio Grande Valley of Tex-
as. But last summer, they turned up in
San Diego County in California. In the
United States, they could potentially cost
$1.4 billion a year in export sales, crop
losses, and treatment expenses.
The new lure resembles the pest's
natural protein food source. Its three com-
ponents are ammonium acetate, pu-
trescine, and methyl butanol. In field
trials in Guatemala, ARS scientists com-
pared sticky cylindrical traps baited with
the new lure to glass McPhail traps bait-
ed with a standard liquid protein lure.
The new lure caught nearly twice as
many Mexican fruit flies as the standard
one. It was also more effective at captur-
ing both males and females. ARS has
filed for patent protection. Earlier, the
scientists developed a Mediterranean fruit

fly lure now approved for use in eradica-
tion programs in Florida. RobertR. Heath,
USDA-ARS Center forMedical, Agricul-
tural, and Veterinary Entomology,
Gainesville, Florida; phone (352) 374-
5735, e-mail bheath@gainesville.usda.

More Dietary Kudos
for Oatrim?
Oatrim is a powdered, soluble oat
fiber that an ARS researcher in Peoria,
Illinois, originally developed as a natu-
ral, low-calorie fat substitute in foods.
But Oatrim may hold other benefits. In
Beltsville, Maryland, volunteers in ARS
diet studies consumed about one-half
cup daily of the powdery substance add-
ed to foods. Researchers found evidence
that Oatrim acted as an antioxidant for
fatty acids. This means it protected fatty
acids crucial to cell membranes and oth-
er cell components. The findings also
suggest Oatrim results in more short-
chain fatty acids being produced in the
colon. These fatty acids may help protect
colon cells from cancer and also reduce
risk of heart disease.
In earlier studies by the Beltsville
researchers, Oatrim reduced body weight,
blood lipids, and systolic blood pressure.
Further, it improved glucose tolerance.
The researchers say Oatrim's antioxi-
dant function comes from something oth-
er than its soluble beta glucans fibers,
known to lower cholesterol. As a fat
substitute, Oatrim is used in some com-
mercial baked goods and cheeses. Labels
identify it as Oatrim or hydrolyzed oat
flour. It is also used as a thickener in a
commercial skim milk sold in East Coast
markets under the brand name Oatri-
Slim. Judith Hallfrisch or Kay Behall,
USDA-ARS Beltsville Human Nutrition
Research Center, Beltsville, Maryland;
phone (301) 504-9014, e-mail

Agricultural Research/March 1999

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