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: February 2000
Frequency: monthly[1989-]
bimonthly[ former jan./feb.-may/june 1953]
monthly[ former july 1953-198]
Subject: Agriculture -- Periodicals   ( lcsh )
Agriculture -- Research -- Periodicals   ( lcsh )
Agriculture -- Periodicals -- United States   ( lcsh )
Agriculture -- Research -- Periodicals -- United States   ( lcsh )
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Statement of Responsibility: U.S. Department of Agriculture.
Dates or Sequential Designation: Began with vol. 1, no. 1 (Jan. 1953).
Issuing Body: Vols. for Jan./Feb.-Nov. 1953 issued by: Agricultural Research Administration; Dec. 1953-<Sept. 1976> by: Agricultural Research Service; <June 1979>-June 1981 by: the Science and Education Administration; July 1981- by: the Agricultural Research Service.
General Note: Description based on: Vol. 27, no. 7 (Jan. 1979).
General Note: Latest issue consulted: Vol. 46, no. 8 (Aug. 1998).
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Bibliographic ID: UF00074949
Volume ID: VID00032
Source Institution: University of Florida
Holding Location: University of Florida
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oclc - 01478561
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issn - 0002-161X

Full Text


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Hydraulic Lifelines

for Soil, Water, and


In the United States, the drought of
the 1930s was followed by periodic
flooding in the 1940s and early 1950s.
These events, plus the postwar baby
boom, its accompanying housing boom,
and other developments, made America's
agricultural community keenly aware of
its responsibility for stewardship of the
soil and water resources needed to meet
increasing demands for food and fiber.
USDA responded in a number of
ways to allow farmers and others to
maintain future resources while increas-
ing food and fiber production through-
out the last half of the 20th century.
Federal research on hydraulic struc-
tures and engineered stream channels has
played a major role in America's food
success story and our farmland's sustain-
ability. In particular, the ARS Hydraulic
Engineering Research Laboratory at
Stillwater, Oklahoma, is recognized
worldwide for modeling, designing, and
evaluating hydraulic structures.
This year, the lab celebrates its 60th
anniversary. Throughout its history, ARS
hydraulic research has played a major
role in developing the knowledge and
procedures for successfully and econom-
ically designing and constructing differ-
ent structures for alleviating flooding and
controlling erosion.
The 1930s-era droughts across the
central United States made clear the need
to keep water and soil in place. To this
end, many thousands of acres of crop-
land have been terraced. Most terraces
are drained by grassed waterways de-
signed to convey excess water to stream
channels without erosion. An estimated
half-million miles of these channels have
been constructed in the United States and
elsewhere. Most, designed over the past
50 years, use engineering criteria devel-
oped and tested at Stillwater.

Natural processes, changes in land use
(especially from development), and
dredging combined to make some stream
channels unstable. Eroding streambeds
and banks destroy land and move excess
sediment downstream. Stream-stabiliz-
ing structures are often required to con-
trol bed erosion and let trees, grasses, and
other vegetation anchor the banks. These
measures, properly applied, allow peo-
ple to productively share the floodplain
with the rest of the ecosystem.
Floods can cause extreme destruction
to cropland and river environments. In
many areas, especially the central United
States, seasonal thunderstorms can dump
very large volumes of water on small
To protect lives, property, and
transportation and communication sys-
tems, the nation has invested about $14
billion in an infrastructure of upland
flood-control reservoirs built with
assistance from USDA and similar
watershed programs. The purpose of
these reservoirs is to temporarily contain
floodwater and release it at a rate the
downstream channel can hold.
Each year, the return on this invest-
ment-in preventing property and crop
losses-is estimated to exceed $800
million. Besides reducing flooding and
sedimentation, the reservoirs provide
recreational fisheries, wildlife habitat,
and wetlands above the containment.
Each upland flood-control reservoir
consists of multiple components. Each
component is a hydraulic structure that
must operate properly if floodwaters are
to be controlled.
Flow to the downstream channel is
conveyed by a principal spillway-
usually a pipe-through the reservoir.
Often, trash racks are needed to prevent
floating flood debris from clogging the
pipe's inlet. ARS scientists have de-
signed, developed, and tested many inlets
and trash racks used worldwide.
To prevent damage to a floodplain
below the reservoir, the tremendous
energy of the large volume of water

released from a reservoir must be
dissipated before it enters the
downstream channel. This is done with
a stilling basin at the spillway's outlet.
The most common type of stilling basin
is the riprap-lined plunge pool into
which water drops as it exits the pipe.
Both the pool and its protective lining
of stone riprap must be properly sized.
It is generally impractical to provide
reservoir storage for extremely large and
infrequent floods. On most watershed
flood-control structures, an auxiliary
spillway safely diverts these large flows
around the dam. These spillways are
usually wide, steep, grass-lined chan-
nels. The channels must be properly
sized to convey the maximum amount
of water without eroding the spillway
and causing it to fail. The Stillwater lab-
oratory has developed exacting design
criteria for these vegetated channels.
Still, in some instances a vegetated
spillway is impractical. Instead, struc-
tural spillways-usually concrete-lined
channels-are used. These spillways
must be properly designed to dissipate
the water's energy before the flow re-
turns to the downstream channel.
Many stilling basin designs are avail-
able. But the SaintAnthony Falls stilling
basin, developed more than 50 years ago
by USDA hydraulic engineer Fred W.
Blaisdell, is still recognized worldwide
as one of the smallest, most efficient,
and most economical designs for drop-
ping water level.
Thousands of flood-control structures
were built from the late 1940s through
the 1990s. Many were designed for 50
years of service and are near the end of
their planned life. Rehabilitating and up-
grading them poses new technical
challenges. ARS scientists will meet
these challenges while protecting the
environment and agriculture.

Darrel M. Temple
Research Leader, Hydraulic
Engineering Research Laboratory
Stillwater, Oklahoma

Agricultural Research/February 2000

February 2000
Vol. 48, No. 2
ISSN 0002-161X

.4A l irdur l kt %1,I /. l i1 published monthly by
[he .grI.ultjuril Reiearch 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
Flo) L P. Horn, Administrator
Agricultural Research Service
Sandy Miller Hays, Director
Information Staff
Editor: Robert Sowers (301) 504-1651
Art Director: William Johnson (301) 504-1659
Photo Editor: Anita Daniels (301) 504-1609
Staff Photographers: Scott Bauer (301) 504-1607
Peggy Greb (301) 504-1620
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
photographs are posted on the World Wide Web
monthly 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 Sunnyside
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
mnajns lfr communications of program informa-
I.n i Br.Ille. 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 (Voice and TDD). USDA is
an equal opportunity provider and employer.

Agricultural Research

Holding Back Floodwaters 4

Crustaceans Can Tell Us To Clean Up Our Act 9

Fungal Protein Slows Broadleaf Weeds


How Attractive Are You? To Mosquitoes, That Is 12

Soy Soothes Cellular Circuits 15

Sunshine Bass Makes a Splash! 16



Biocatalysis: Using Enzymes To Produce

New Products 21

The Nose Knows 22

Science Update 23

Cover: This 1/4-inch-long crustacean, Hyalella azteca, is common in aquatic systems
and is used by scientists as an indicator of environmental health and water quality in
streams, lakes, and other bodies of water. Story on page 9.
Photo by Scott Bauer. (K8451-1)

In the next issue!

weed species are under attack by insects released by ARS scientists. The insects
were chosen based on their ability to do the most damage to the targeted weed
and the least damage to anything else.

jellyfish glow has been inserted into the food bacterium E. coli, making it visible to
food safety scientists.

Agricultural Research/February 2000

F rom a distance, the 50-acre
ARS Hydraulic Engineering
Research Laboratory in Still-
water, Oklahoma, looks more
like an archeological excavation than a
world-class research facility. The labo-
ratory and its many outbuildings and
grounds are covered with all types of
hydraulic structures. Hydraulics is the
science that deals with the motion of
water and other liquids.
Recognized worldwide for modeling,
designing, and engineering hydraulic
structures for agriculture, the Stillwater
facility today specializes in studying how
water erodes spillways and forms gaps
in earthen dam walls or embankments.
The lab is set to play one of its greatest
roles-assisting in the rehabilitation and
revitalization of thousands of earthen
dams in the United States.
"The 3,000-acre Lake Carl Blackwell
located next to the laboratory provides
the water used for simulating and test-
ing hydraulic structures," says the ARS
laboratory's research leader Darrel M.
Temple. "The facilities are ample for
conducting full-size prototype tests of
many hydraulic structures, like full-scale
vegetated channels."
Such a readily available and abundant
water supply allows the laboratory's sci-
entists to generate the high waterflow
rates-up to 130 cubic feet per second-
needed to simulate the forces that cause
holes to form in earthen spillways and
"The laboratory's unique topography
and proximity to the lake make it possi-
ble to deliver these high rates of
waterflow," he says.
Water used for experiments can be
diverted to the outdoor laboratory or to
one of three buildings where the ARS
scientists model and test hydraulic
"Designs for hydraulic structures are
typically tested in one of the buildings
that have various-sized channels," he
says. "After we fine-tune the scale model
indoors, we often build and test it

Aerial view of the AKS Hydraulic Engineering Research Laboratory facility with Lake
Carl Blackwell in the background. An earthen dam running along the shoreline separates
and protects the facility from the lake, which is at a higher elevation.

outdoors under conditions that more
closely match field conditions."
Of current concern to the Stillwater
lab are the nation's earthen dams. Amer-
ica's countryside is dotted with these
small dams. These earthen dams protect
the watershed. Many supply water to
municipalities. They also prevent floods;
provide water for irrigation, recreation,
fish and wildlife habitats, and ground-
water recharge; and improve water
"Each year," says Temple, "these res-
ervoirs provide Americans with more
than $800 million in benefits."
Dams store and trap sediment and
prevent excess runoff from damaging

land downstream. As dams age, they can
fill up with sediment and become un-
sound structurally, says Temple, who has
spent 23 years as an ARS hydraulic engi-
neer working at the Stillwater laboratory.
Temple says, "Many of the more than
10,000 flood-control structures in the
United States were designed to have a 50-
year service life. About two-thirds of
them were designed before 1962 to
protect communities and rural lands
Today, these upstream flood-control
dams are in urgent need of revitalization
and rehabilitation. Over the next 10 years,
more than a thousand will need signifi-
cant repairs and modification. Temple

Agricultural Research/February 2000

says that "many no longer work as effi-
ciently as they should. That's mainly
because of aging, sediment filling, and
changes in what the land has been used
for. These conditions could not have
been anticipated during design and con-

SITES Software Program
The expertise and database amassed by
the ARS laboratory over its 60 years of
research are needed to rehabilitate these
dams. And USDA's Natural Resources
Conservation Service (NRCS) will work
cooperatively with the Stillwater lab to
develop technologies for rehabilitating
and revitalizing the dams.

Agricultural Research/February 2000

The software program documenting
these technologies is called SITES (not
an acronym). "SITES combines the
principles of geology, hydrology, soil
science, and physics to predict the
performance of spillways-both prin-
cipal and auxiliary," says Temple.
"The current software program pre-
dicts how an earthen spillway will per-
form and evaluates its potential for
failure. Future versions will incorporate
current research that will predict the
damage that results from embankment
overtopping. The likelihood of an earthen
dam failing will be determined from the
erosion that occurs on the downstream
face of the dam."

Adding to the urgency of this problem
is the increased risk to life and property
from changes in upstream and down-
stream land use since the dams were
"When these dams were built, most
of the surrounding areas were rural," he
says. "As communities expanded and
homes were built in known flood plains,
the system of reservoir dams-original-
ly intended to protect crops and farm-
land-now safeguards houses, property,
and lives."

A High Price To Pay
When dams fail, land is often devas-
tated, homes and roads can be destroyed,
and people can die.
Temple remembers one example of
dam failure that occurred in May 1983
at Black Creek in Mississippi. The dam
failed because of erosion in the emergen-
cy spillway. The flood that caused the
failure was generated by heavy rain-
storms that dumped 14 inches of water
on the watershed.
"The spillway was originally 5 feet
deep and 100 feet wide. The reservoir
was full of water before the dam failed.
After the spillway breached, it was about
190 feet wide and 40 feet deep. The
reservoir drained, releasing 4,500 acre-
feet of water at a peak rate of 9,000 to
12,000 cubic feet per second to the
downstream flood plain," says Temple.
He adds, "Luckily, no homes were
immediately downstream of the reser-
voir. No loss of life occurred. However,
the water and sediment released caused
substantial damage downstream."
A county bridge about 1-1/2 miles
downstream washed out, and the road-
way was severely damaged. Two down-
stream ditch bank levees were breached.
The water caused massive erosion and
sediment deposits in agricultural fields.
"If a breaching like this occurred
today in a reservoir where housing had
encroached on the downstream flood
plain, loss of life would be likely," he

"The Mississippi dam failure drives
home the point that dams are a vital part
of our nation's infrastructure, like roads,
bridges, and sewage-treatment plants,"
says ARS hydraulic engineer Gregory J.
Hanson, who has worked for 15 years at
the Stillwater laboratory. "An estimated
$8.5 billion infrastructure in 1997 dol-
lars has been developed in the form of
these earthen dam structures," he says.
"As ARS scientists, we work closely
with and respond to the needs of NRCS
nationally," Temple says. "The SITES
software project is the most recent ex-
ample of this cooperation and response."
Developed from both ARS laboratory
studies and field data, the SITES soft-
ware now provides engineers with a tool
for analyzing and predicting the perfor-
mance of vegetated earth spillways like
those used on many watershed flood-con-
trol reservoirs.
"SITES is a model used for designing
new structures or for analyzing how ex-

isting structures perform," he says. "The
model considers how runoff from rain-
storms affects the structures and the
performance and failure potential for veg-
etated spillways. Future refinements will
allow us to evaluate performance and
failure potential for dams overtopped by
extreme flood flows."

How SITES Works
The SITES software evaluates spill-
way surface and subsurface conditions
and determines the location and nature
of the erosion posing the greatest risk of
"New technology is incorporated into
the model, such as the use of an index-
called a headcut erodibility index-to
describe the resistance of the exposed
geologic materials to erosive attack dur-
ing the latter stage of the erosion pro-
cess," says Temple.
The SITES software also uses mathe-
matical curves for calculating waterflow

rates of vegetated auxiliary spillways.
These curves take into consideration the
flow-retarding effects of vegetation in
the spillway.
"These capabilities place the SITES
software on the leading edge of technol-
ogy of earth spillway design and anal-
ysis," he says.
"The spillway erosion prediction por-
tion of SITES is based, in part, on data
cooperatively obtained by the long-term
joint effort of ARS and NRCS," says
ARS hydraulic engineer Kerry M. Rob-
inson. He has worked at the Stillwater
laboratory for 17 years.
Started in 1983, the SITES project
was aimed at gathering data from field
spillways that had significant waterflow
or damage or both. At the same time,
ARS scientists at the Stillwater labora-
tory began large-scale lab and field stud-
ies to examine the processes associated
with the erosion and overtopping of
earthen spillways.

Agricultural Research/February 2000

"The SITES water resources site anal-
ysis software, released by NRCS in ear-
ly 1997, significantly changed that agen-
cy's approach to analyzing spillways,"
says Temple.
"We're presently refining the
hydrologic criteria-the quantity of
rainfall used for dam and spillway de-
sign-for use with this software."
Since SITE's 1997 release, the two
federal agencies have been cooperating
with Kansas State University, Manhat-
tan, to simplify how the model can be
applied. An advanced graphic program
assists users in applying the model by
guiding them through the needed model
inputs and graphically displaying the re-
sults of computations on the monitor of
the computer.
"For example," Temple says, "if a user
changes the width of the spillway, the
impact of that change will automatically
show up in other aspects of design and
performance-sort of a ripple effect."

Agricultural Research/February 2000

He says, "This will allow the user to
conveniently compare and contrast the
technical implications of various design
alternatives. It includes display screens
for data entry and for both text and
graphical output."
At the present time, this enhance-
ment-or interface-applies only to a
reservoir site or existing structure with
relatively simple upstream watershed
conditions. Work is currently under way
to expand the interface to include more
complex watersheds with other reser-
voirs farther upstream.
"We expect to have this expanded
version available by late 2000," Temple
says. "The first test version of the model
will be completed by February 2000.
"Research efforts are in progress to
expand the SITES technology to allow
users to model earthen embankments to
determine what conditions will cause
them to fail. Aging of these dams,
combined with increasing population

densities and increased environmental
concerns, will generate many challenges
for each of us involved in this effort."-
By Hank Becker, ARS.
This research is part of Water Quality
and Management, an ARS National Pro-
gram (#201) described on the World Wide
Web at
Darrel M. Temple, Gregory J. Hanson,
and Kerry M. Robinson are in the USDA-
ARS Hydraulic Engineering Research
Laboratory, 1301 N. Western St., Still-
water, OK 74075-2714; phone (405)
624-4135, ext. 226/223/225, fax (405)
624-4136, e-mail
temple @pswcrl. ars.
ghanson @pswcrl. ars. usda. gov
More information about SITES can be
obtained on the World Wide Web at http:/
common/sites/sites.html. *

This step baffle trash rack on the spillway inlet of Boomer Lake prevent
plugging the inlet by forcing the water to enter upwards through baffles
rack flows through the principal spillway conduit to the stream channel

So Many Structures, So Many Needs

Scientists at the ARS Hydraulic Engineering Research
Laboratory, Stillwater, Oklahoma, look at water in terms of
physics and math. The concepts and principles they have
developed over the last 60 years have become the standards
for the best design for safe, economical, and lasting hydraulic
structures and channels for agriculture that are in harmony with
"In the United States, USDA's Natural Resources Conser-
vation Service has assisted in constructing tens of thousands
of these hydraulic structures, based on the procedures devel-
oped at the ARS lab," says ARS hydraulic engineer Gregory J.
One area of specialization is grass-lined waterways-natural
alternatives to concrete and rock and other materials considered
by some to be ugly and costly-for draining terraced agri-
cultural lands. Hanson says the laboratory's worldwide
leadership in designing vegetation-lined waterways is a lasting
"These vegetation-lined waterways are used today to safe-
ly convey runoff from more than 3 million acres through
500,000 miles of waterways," he says. "Many were built by
NRCS. The grassed-waterway design procedures developed
by ARS are virtually the only reliable ones available, originat-
ing from a solid experimental background."
The grassed-waterway design procedures are the result of a
series of tests on vegetated channels. "Among other things,
these tests accounted for resistance to waterflow caused by
vegetation and the geometry of the channel. Engineers world-
wide rely on these studies when they design vegetated chan-
nels," he says.
Hundreds of tests on the hydraulic performance of struc-
tures and channels have been performed at the Stillwater lab.

Some better known products re-
sulting from these tests and the
team effort of USDA's agencies
include design criteria for energy-
dissipating structures, such as
stilling basins, which slow
down the flow velocity and re-
duce the erosive action of water
S plunge pools, which dissi-
pate the erosive energy of falling
s floating debris from hood inlets, which allow a
. Water entering the trash
downstream of the dam. pipe to convey water more effi-
step baffle trash racks,
which allow water to drain from
a reservoir and which don't get
plugged with floating debris
flow-measurement flumes, which accurately determine
the rate of waterflow
rock chutes, which are loose rock structures that safely
transfer water to lower elevations (photo on page 6).
"This is just a partial list of the many hydraulic structures
studied and developed here," Hanson says.
Hanson's colleague, ARS hydraulic engineer Kerry M. Rob-
inson recently tested a hydraulic model of a new water supply
dam. It uses roller-compacted concrete for a structure being
built near Randleman, North Carolina.
"With this design, the auxiliary spillway can be placed over
the dam, with a stepped surface on the downstream side of the
dam. The stepped surface decreases the velocity of water and
reduces the energy of the flowing water as it goes over the
spillway," he says.
Design modifications resulting from Robinson's study saved
about $2 million on this project.
Besides structures, Hanson and colleagues have developed
a circular jet test that uses a patented device to directly mea-
sure soil erodibility by water in the field or laboratory (photo
on page 7).
"The device uses a jet of water to form a cavity in the soil,"
he says. "The soil's resistance to erosion is calculated from the
difference between the original and the eroded soil profile. This
difference is expressed as a jet index."
The jet device can measure the erosion potential of a soil in
vegetated channels, road embankments, dams, spillways, and
construction sites.
The device has been field and lab tested on several soils at
various rates of waterflow. It was developed in conjunction
with the SITES software for analyzing earth spillways.-By
Hank Becker, ARS. +

Agricultural Research/February 2000

I Crustacean Can Tell Us ToCleanUpOur Act


your water may seem disgust-
ing, but Agricultural Research
Service scientist Charles M.
Cooper hopes to find a whole lot
of healthy critters in his water-
especially if they're Hyalella azteca.
That's because these crustaceans are
a sign of good water quality. If Cooper
finds healthy Hyalella swimming in
streams and lakes, he knows the water is
clean and not exceeding critical levels
of agricultural chemicals that sometimes
run off from fields into water supplies.
Hyalella have become a valuable tool
since 1972, when the first Clean Water
Act was passed. Scientists and regulators
have used many approaches to measure
water quality and to clean contaminated
But Cooper, an ecologist in the
USDA-ARS Water Quality and Ecology
Research Unit at Oxford, Mississippi,
has turned to nature for this task-
specifically to Hyalella.
The 1/8- to 1/4-inch-long crustaceans
are commonly found in lakes, ponds, and
streams throughout North America. Hy-
alella consume de-
caying plant matter
and can be found SCOTTBAUER (K84633)
swimming in the wa-
ter or burrowing into
sediment. They are an
important link in the
aquatic food chain
and a food source for
several predators, in-
cluding fish and vari-
ous invertebrates.
Tiny Hyalella offer
many advantages as a
biological indicator of
environmental quali-
ty. The organisms are
easy to raise, repro-
duce readily, and are
representative of spe-
cies of invertebrates
found in most water Ecologists Charlie
Thighman Lake fi

systems. "They are inexpensive and easy
to work with," says Cooper.
The tiny crustaceans provide biolog-
ical measurements of water quality so
researchers don't have to rely solely on
chemical and physical measurements.
Hyalella are collected with other small
animals common to water systems and
are examined to determine whether an
ecosystem is functioning properly. Sci-
entists can then focus their research on
the areas that are potentially problematic.
Hyalella are also used in laboratory
experiments. Cooper and ecologist Scott
S. Knight expose them to various con-
centrations of chemicals to evaluate and
model responses to actual exposures in
streams and lakes.
They run toxicity tests using known
and controlled mixtures of multiple
chemicals to determine critical levels of
contamination. Then they compare their
lab results to those obtained in outdoor
bodies of water to determine if the lab
data reflect what is happening in the real
Monitoring water quality through
chemical and physical measures reveals

* Cooper (left) and Scott Knight sample bottom sedi
or small animals that indicate ecosystem health.

Hyalella azteca on an underwater
leaf litter culture

the effects of improved conservation
farming practices. The biological meth-
od used by Cooper, however, confirms
whether these practices are improving
the overall health of the ecosystem. In
the end, results are used to make rec-
ommendations to farmers to promote a
healthy, clean environment.-By Sarah
Tarshis, formerly
with ARS.
This research is
part of Water Quality
and Management, an
ARS National Pro-
gram (#201) de-
scribed on the World
Wide Web at http://
Charles M. Coo-
per and Scott S.
Knight are in the
Quality and Ecology
Research Unit, P.O.
Box 1157, Oxford, MS
38655-1157; phone
(662) 232-2935, fax
(662) 232-2915, e-
ments in
mail cooper@sedlab. *

Agricultural Research/February 2000

Fungal Protein Slows

Broadleaf Weeds

You have to give credit to stubborn weeds like dandeli-
on or knapweed. No matter how many times you pull,
spray, or plow them up, they seem to come back for
Now researchers are trying a different approach.
Using a natural protein from a soil fungus, they've developed
a potential herbicide that causes the weeds' leaf cells to kill
themselves. In greenhouse experiments, this mass cellular sui-
cide killed the plants' leaves within 24 hours.
"It's the first case I know of where a protein like this has
been used as a foliar herbicide to induce
PEGGY GREB (K8703-3)
a hypersensitive response," says Bryan
Bailey, a plant pathologist with USDA's
Agricultural Research Service in
Beltsville, Maryland.
"The idea here," he adds, "is to get
the plant to kill itself rather than using
chemical herbicides that may be less en-
vironmentally friendly."
Bailey and ARS colleagues Nichole
O'Neill, Jim Anderson, and Patricia
Birkhold, now with DowElanco, will re-
port their findings in the January/Feb-
ruary issue of Weed Science.
They first discovered the protein,
called Nep1, about 5 years ago in sec-
retions of the fungus Fusarium oxyspo-
rum. Some forms of this fungus cause
wilt diseases that diminish yields of
corn, cotton, tomatoes, and other crops.
However, by removing the protein-
making gene of F oxysporum and then
infecting plants with the altered fungus,
the researchers showed that Nep 1 plays
no part in causing disease. Harmless Fu- The Nepl protein is pu
sarium strains also produce the protein filtrates (shown in the
fungus Fusarium oxysp
with no ill effect to plants, notes Bailey. pathologist Bryan Bail
Yet, when purified from a broth spotted knapweed that
culture of Fusarium and sprayed on or a day earlier. The heal
injected into dandelions, yellow star- was not sprayed.
thistles, and several other broadleaf
plants, Nepl becomes a powerful natural herbicide. The team
first observed the phenomenon in studies late last year.
However, not all broadleaf plants respond the same.
One way weeds fight off disease-causing organisms is with
a built-in defense called a hypersensitive response. It triggers
the sudden collapse of cells immediately around an invading
pathogen. This helps to cordon off further infection. With Nep 1,
however, this defense mechanism goes into maximum
overdrive, sacrificing so many cells that the leaves die 3 to 24
hours later.


"I look at this as a different mechanism than that triggered
by an herbicide," says Anderson, a plant physiologist at ARS'
Weed Science Laboratory in Beltsville. The weed "turns on its
defensive response to such a high degree that it kills itself."

Potential Uses of Nepl
Because it isn't harmful to monocot crops-such as corn,
wheat, barley, rye, or turfgrass-Nep 1 may prove to be a natural
alternative to some conventional synthetic herbicides. It could
be used to control or kill off cover crops, for example, hairy
vetch, which is very sensitive to the
"If you could use this in an organic
farming situation, I think that would be
great because organic farmers have lim-
ited weed control choices right now,"
says Bailey.
According to Mark Lipson, policy
program director for the Organic Farm-
ing Research Foundation (OFRF), "Bio-
pesticides in general are very important
transitional tools to organic systems. But
they are not, and should not be, essential
in the long run."
An organic farmer, he explains, might
apply a biopesticide as a last resort or to
complement other organic weed con-
trols, such as using cover crops, mulches,
burning, or cultivation.
The ARS researchers envision using
... .., Nep 1 to kill or weaken dicot (broadleaf)
weeds like yellow starthistle, northern
joint vetch, and spotted knapweed. In
rangeland or pasture areas, for example,
ied from culture this could give grasses and other forages
ri dishes) of the a chance to reclaim lost ground or
um. Above, plant
holds a damaged resources.
is sprayed with Nepl "If you could knock the weed back
spotted knapweed and give it a 1- or 2-week delay," says
Bailey, "then competing plants could
shade it out." Nepl could also be sprayed
on weeds between rows of monocots like corn and have the
same effect, he adds.
Another potential use is combining Nepl with the herbicides
RoundUp (glyphosate) and 2,4-D, or 2,4-dichlorophenoxy
acetic acid.
Used as an additive, Nep1 appears to give these herbicides
a boost that damages weeds faster than in instances when the
chemicals are used alone. This may also reduce the amount of
chemical needed, a possibility the scientists are now exploring
in lab and greenhouse experiments.

Agricultural Research/February 2000

In trials last summer, RoundUp applied alone took about 2
weeks to kill the weeds. But with small doses of Nepl added,
damage was visible overnight and the plant didn't grow back,
says Bailey.
Between 5 and 20 parts per million of Nepl are used with
water, along with Stilwet, a synthetic surfactant. It helps Nep 1
stay glued to the leaf surface where it can penetrate natural
openings like stomata.
For organic farming purposes, though, a naturally derived
surfactant would be needed, notes Anderson. While common
biopesticide ingredients, surfactants of a synthetic nature "can
make a formulation unacceptable" for organic farming, says
Jane Sooby, OFRF's technical director.

Biodegradable Weed Wacker
Outdoors, Nep1 is stable on plant leaves for about 24 hours.
Though environmental factors like sunlight or microbes can
break apart its amino acid structure, the protein is generally
absorbed by plants within 30 minutes of contact. Researchers
believe the havoc begins when Nepl physically contacts re-
ceptors on cells, setting off a biochemical chain reaction that
soon kills the leaf.
Researchers also suspect broadleaf plant cells are more likely
than monocot cells to harbor receptors for detecting Nepl.
Monocots may escape harm because their defenses either don't
recognize Nepi or don't react with it in the same way as di-
The initial damage caused in dicots by Nepl is restricted to
the leaves. That's because other areas, like the stem, don't have
stomatal openings. That same feature, Bailey notes, may allow
Nep to be used as a natural leaf dessicant in certain agricultural
situations, like harvesting lint from cotton-a dicot crop.
A nice feature of Nep is that it won't hang around long in
the environment. Though it can last a few months stored in a
refrigerator, it readily breaks down in a field. It's also unlikely
to be toxic to humans or animals.
However, because Nepl is a protein, researchers will still
have to check for potential allergenicity. And the cost of mass-
producing the fungus is uncertain, says Anderson.
On the flip side, Nep 1 "makes up 90 percent of all protein
the fungus produces," Bailey notes. "It's readily available and
doesn't require a lot of processing, and you can take its partially
purified form and use it."
For dandelions, spotted knapweeds, and other pesky weeds,
this can only mean more troubled times ahead.-By Jan
Suszkiw, ARS.
This research is part of Crop Protection and Quarantine,
an ARS National Program (#304) described on the World Wide
Web at
Scientists mentioned in this article can be contacted through
Jan Suszkiw, USDA-ARS Information Staff, 5601 Sunnyside

Avenue, Beltsville, MD 20705-5129; phone (301) 504-1630,
fax (301) 504-1641, +

Technician Dave Clark (left) and research associate Sarah Keates of
the Weed Science Laboratory in Beltsville, Maryland, apply Nepl to
a planting of the ground cover hairy vetch. Nepl killed the vetch
foliage within 24 hours of treatment (insert shows treated and
untreated vetch).

Agricultural Research/February 2000

S or years people have known about animal attraction.
Perfume and cologne are the primary "weapons of
choice" many use to attract the opposite sex.
SBut \e don't need to do an thing to attract insects.
W\e 2gie off hundreds. maybe thousands, of natural scents that
bugs. particularly. mosquitoes, just loie.
"So far. \\e have found more than 3-10 different chenucal
scents produced b\ human skin. and some of these attract
mosquitoes." sa\s ARS chemist Ulrich R. Bernier.
"Scientists have knto\n for Nears that lactic acid-present
on human skin-is a mosquito attractant. So far, this is true for
onl. a handful of species, one of w which is the yellow\ fe\er
mosquito. Aedes aegvpii. Fining \\ hat attracts mosquitoes \\ 1ll
ultimately\ help us find \\a\s to control them." Bernier is \\ith
the ARS Center for Medical, Agricultural. and Veterinary
Entomology's Mosquito and Fly Research Unit in Gaines\ ille.

For more than 30 years, scientists have been searching for
compounds that attract mosquitoes. Bernier started his quest
back in 1992, when ARS research leader Donald R. Barnard,
head of the Gainesville unit. arranged funding of his doctoral
research aimed at fininng which chemicals or scents on a;
human-handled petr dish \were dri\ ing mosquitoes craz\. It
\as e'. ident to Bernier that a glass petr dish readily adsorbed
some human scents. From then on. using glass to collect
samples became the foundation of Bernier's research.
"I developed a technique using glass beads to help me iden-
tif. organic compounds from humans that are attractive to
mosquitoes." says Bernier. "The beads are rubbed repeatedly
between human palms to collect skin emanations The beads
allow Bernier to take samples \w without collecting excess wa-
ter. which distorts the chemical analysis.
The Gaines\ille scientists are testing indi\ idual scents and
combinations for attract\ eness to different mosquito species.

Agricultural Research/February 2000

They use an olfactometer, a cage separated by a screen, where
mosquitoes are placed on one side and an attractant is pumped
through the other, to see if mosquitoes will come to the screen.
Bernier says it's difficult to find an attractant because unlike a
pheromone (a single substance that attracts one sex of an in-
sect species to another), it appears that multiple compounds or
kairomones (care-ah-mones) are needed to attract mosquitoes.

Simply Irresistible!
Since 1997, Bernier has been combining different blends
and screening them at different levels to see which blends draw
mosquitoes best. A promising scent is later combined and test-
ed in a blend. "Some blends beat out a human-handled dish
every time," says Bernier. "Those blends have proven to be
some of the most efficient and consistent attractants we've used.
We can get about 90 percent of the mosquitoes in the cage to
come to the mixture. This is impressive considering my own
arm and hand attract only about 70 percent of them.
"We still don't have a perfect blend," Bernier notes. "But,
we're a lot closer than we've ever been." Several promising
blends, for which Bernier has filed a patent, are combinations
of human-produced odors with and without lactic acid.
In 1968, Gainesville scientists discovered lactic acid is an
attractant for the yellowfever mosquito. At that time, carbon
dioxide (C02) was also thought to be necessary to attract mos-
quitoes. Bernier says what might be the single most important
discovery about these blends is they don't use CO2, unlike most
other blends or attractants. CO2 is a bother, he says, because a
person would have to lug a huge tank or a brick of dry ice into
the field. All of the specific chemical combinations he's isolated
for both the yellowfever mosquito and Anopheles albimanus,
a tropical mosquito that spreads malaria, don't need the CO2.
"It's difficult improving synthetic blends when you increase
the number of chemical compounds in the blends," says Bernier.
"Two components will look as good as four, unless you put
them in direct competition with human hands. We're working
toward improving the blends for attracting yellowfever mosqui-
toes and adjusting the blends to attract other mosquito species."
Finding a blend and testing it isn't all that has to be done.
"You have to have consistency when doing tests," says Bar-
nard. "Many things could affect why a blend is attractive or
not. For example," he says, "we use three olfactometer cages,
stacked one on top of the other. How do we know mosquito
responses will be the same in the top cage as in the bottom?
We test to see if the location or position of the cages affects the
"Time of day is also extremely important. Mosquitoes tend
to have cycles when they are more active and will or will not
feed," says Barnard. To minimize experimental error," Barnard
says, "we test the blends under circumstances where light
conditions, air temperature, airspeed, and so on are controlled."

What Else Do Mosquitoes Like?
Entomologist Daniel L. Kline tested the attractiveness of
socks worn by humans. The results: Mosquitoes love them. "I
wore the socks for 12 hours on 3 consecutive days. When I
wasn't wearing the socks, I put them in a sealed plastic bag,"
says Kline. "I also found mosquitoes love Limburger cheese.
Interestingly enough, the main ingredient in the cheese is a
bacterium that can be found on the human foot," he says. Inci-
dentally, Limburger cheese was first made in The Netherlands
by monks. They trampled the cheese with their feet to get the
finished product.
Kline tested responses of female Aedes aegypti to the socks,
human hands, and Limburger cheese. He used females because
only they will take blood. They need it for reproduction.
In field studies, Kline says the socks alone attracted very
few mosquitoes. However, a significant increase occurred to
CO2-baited traps when combined with a worn sock for most
mosquitoes, including species of Aedes, Anopheles, Coquil-
lettidia, Culex, Culiseta, and Psorophora-major disease-
transmitting mosquitoes. Mosquito responses were favorable
in the olfactometer, but the human hand still attracted the most.
"If we can isolate the chemical scent in the socks, then we can
use that as an additional attractant," says Kline.

Entomologist Donald Barnard demonstrates the attraction of
female yellowfever mosquitoes to his hand in an olfactometer. The
olfactometer contains a screen separating the attractant (in this
case, his hand) from the mosquitoes.

Why Attract Them?
Attractants can be used as nontoxic baits in mosquito traps
for surveillance purposes. "Many countries, particularly under-
developed ones, need improved detection and population moni-
toring in areas where mosquitoes pose high risks of transmitting

Agricultural Research/February 2000

diseases like yellow fever, dengue, and
malaria," says Barnard. "If we can attract
the mosquitoes to a trap, we can use this
information to assess the mosquito distri-
bution and population and develop ways
to control them."
Also, Barnard says if you are using
conventional traps to look for a particular
mosquito that transmits a disease, but you
don't find that mosquito in your trap, that
doesn't mean the mosquito isn't in the
You have to make sure that the at-
tractant you're using works for that par-
ticular mosquito. What may be attractive
to one species may not be for another.
For example, some species may be
attracted to human blood while others
may feed only on the blood of wild or
domestic animals.
Since there are 4-6 dozen mosquitoes
out of 2,700 worldwide that transmit dis-
eases, it can be tricky to pinpoint an at-
tractant, Barnard says.

PEGGY GREB (K8748-1)

Entomologist vamei Nune inspects
mosquitoes caught in a collection device.
The bait used was a combination of a worn
sock and carbon dioxide.

After being rubbed between palms to pick
up human scents, glass beads are carefully
loaded into a glass insert.

The potential also exists to use traps
for reducing mosquito populations with
minimal dependence on chemical
"Our hope is to reduce reliance on
pesticides, says Barnard. "We expect
attractant-enhanced traps to eventually
surpass pesticides in effectiveness. We
hope to develop stand-alone traps that
can be used by homeowners or livestock
"In the future," he adds, "we hope to
develop personal protection technology
based on this research. By knowing what
attracts mosquitoes, we can develop
better defenses against them.
"One day we hope to develop sys-
temic repellents that can be taken orally
or devices that can be worn to neutralize
the attractive effects of a person to a
Animals also act as a magnet for
mosquitoes. "The next phase of our re-
search will be to look at what attracts
mosquitoes to livestock," says Barnard.
"We're looking at mosquitoes that
bite both livestock and people because
mosquitoes spread some viruses be-
tween the two. Like St. Louis enceph-
alitis, for example: A mosquito bites an
infected mourning dove and later bites
a human."
Ultimately, a better understanding of
mosquito attraction should help in
developing more effective, environ-
mentally safe repellents for protection

Chemist Ulrich Bernier examines glass
beads that have adsorbed human scents.
The glass insert containing the beads is
ready to be installed in a gas chromato-
graph to identify the scents.

from insects that prey on humans and
livestock.-By Tara Weaver-Missick,
This research is part of Arthropod
Pests of Animals and Humans, an ARS
National Program (#104) described on
the World Wide Web at http://www.nps.
Donald R. Barnard, Ulrich R.
Bernier, and Daniel L. Kline are with the
USDA-ARS Center for Medical, Agri-
cultural, and Veterinary Entomology,
Mosquito and Fly Research Unit, 1700
SW 23rd Drive, Gainesville, FL 32604;
phone (352) 374-5931, fax (352) 374-
5922, e-mail
ubernier@gainesville. usda. ufl. edu *

Agricultural Research/February 2000


Soy Soothes Cellular Circuits

Y ou'vejust sat down to dinner, and the phone rings. A pushy salesperson. Then your neighbor

starts his lawn mower. After dinner, your daughter turns up the volume on her heavy metal CD. A

little later your 3-year-old son throws a tantrum over going to bed. Jangled?

Perhaps that's how your cells feel when too many chemical
signals-too many orders to do something-get through. And
your cells may react before they should. For example, if an
order to divide gets "heard" by too many
cells too often, it can lead to unrestrained PEGGY GREB (K8744-1)
growth, as in cancer, or an overactive im-
mune response.
Likewise, if your blood cells are told
to react to certain chemicals in the blood
but tend to overreact, it can lead to car-
diovascular disease and heart attack.
Researchers now believe that poor
regulation of signal transduction is a ma-
jor factor behind some chronic diseases.
Miraculously, cells usually do a pretty
good job of filtering out noise and staying
on task. "Foods play an important role,"
says ARS nutrition chemist Norberta
Schoene. Soy, with its isoflavones like
genistein and daidzein, is an example of
a food that can affect cell response.
Japanese diets average about 10 times
more soy than North American diets. And
Japanese people have a lower incidence
of cancer and heart disease. Tofu, tem-
peh, and miso are some soy foods rich in
isoflavones. Chemist Norberta Sc
In the late 1980s, Schoene says, re- samples for analysis
searchers showed in test tube studies that These blood samples
rats and used to stud
genistein inhibits enzymes that connect isoflavones on plate
the lines of communication from the cell's
membrane into its interior. Her recent
study gives the first direct evidence of this
dampening effect in an animal.
Schoene fed young rats diets contain-
ing soy protein with high or low genistein
levels for 4 weeks. Then she measured the response of the an-
imals' blood platelets in three different tests. Platelets are quite
sensitive to outside signals because they have to clump together
to prevent blood loss. So they serve as a good model for study-
ing cell signaling, she explains.

ly t
et fu

First, animals getting the genistein-enriched diet had
significantly more platelets in the unactivated disk shape. Those
getting little genistein had more of the rounder, activated
platelets. "That's consistent with reports
that platelets are apparently larger in
activating environments such as those re-
sulting from smoking, diabetes, and heart
disease," she says.
Second, hydrogen peroxide produc-
tion-a necessary step in signal trans-
duction-decreased in blood platelets of
rats on the high-genistein diet.
Third, the signal-carrying proteins
from the high-genistein rats were less
likely to have phosphate groups attached.
"These phosphate groups help build the
protein scaffolding that carries the
signal," says Schoene.
Her hypothesis: "Isoflavones may
reduce overresponsive, dysfunctional
signaling that leads to some chronic
Schoene says the genistein-rich diets
had the equivalent of twice the average
Japanese genistein intake. But some
L.k ,.S Japanese eat as much as the rats got, she
ne prepares blood noted.
a flow cytometer. The genistein-poor diet, on the other
re obtained from hand, was equivalent to the U.S. diet in
ie effects of
nation. genistein levels.-By Judy McBride,
This research is part of Human Nu-
trition, an ARS National Program (#107)
described on the World Wide Web at
Norberta W Schoene is at the USDA-ARS Nutrient Require-
ments and Functions Laboratory, Bldg. 307, Room 215, 10300
Baltimore Ave., Beltsville, MD 20705-2350; phone (301) 504-
8388, fax (301) 504-9062, e-mail schoene@ 307.bhnrc.arsusda.
gov. *

Agricultural Research/February 2000

Sunshine Bass Makes a Splash!

I n the early 1980s, East Coast fishermen peddled striped
bass to fish markets, netting up to 14.7 million pounds
annually. Eventually, however, overfishing and pollution
essentially destroyed the industry.
Fish farmers of the East Coast, Arkansas, and Califor-
nia thought the fish could make a comeback in aquaculture
ponds and fill a market vacuum. Thanks partly to research,
they were right. Since 1984, when production was at only
10,000 pounds a year, it has increased to more than 15 mil-
lion pounds annually.
Actually, it's a hybrid fish called sunshine bass that's mak-
ing the splash. A cross between male striped bass and female
white bass, sunshine bass grow faster than either parent.
Fish farmers Mike Freeze of Keo, Arkansas, and Jackson
Currie of Wilmot, Arkansas, are among the leaders in the
sunshine bass industry. Freeze specializes in spawning the
parental stocks. He and Currie then nurture the just-hatched
fry from the time they are barely visible-2 to 5 millimeters
long-until about 35 days later
when they're 3/4- to 1-inch-long GERALD LUDWIG (K8749-2)
fingerlings. They then sell the juve-
nile fish to other farmers around the
world who grow them to market size
at 1.5 to 2 pounds in 18 months.
To identify production problems
and find solutions, Gerald M.
Ludwig, a fish biologist at ARS' Na-
tional Aquaculture Research Center
at Stuttgart, Arkansas, keeps in con-
tact with Freeze, Currie, and other
producers. "We learn as we bounce
ideas off each other," says Currie.
In the early 1980s, after experi-
menting with raising microscopic
animals called rotifers as fish feed,
Currie turned some equipment over
to Ludwig. Putting the equipment
to good use, Ludwig steadily found
ways to improve the survival rate
of young fish.
"Until a few years ago, we could
achieve only a 10-percent survival
rate of fry," said Ludwig. "Now the
norm is 30 percent, and some nurs-
ery pond managers do much better." At the ARS National Aqu
Ludwig and his colleagues de- Stuttgart, Arkansas, fish I
veloped information to help fry examines a market-size su


culturists time the stocking of ponds so the fish can eat and
grow fast enough to avoid being eaten by zooplankton-some
of the very creatures they must consume to survive. Graphs
and equations Ludwig developed show the pivotal window of
opportunity when two other essential food sources, rotifers
and minute crustaceans called copepod nauplii, become
abundant and zooplankton are still too small to be a threat.
The equations take into account pond temperature, which
strongly influences the buildup of rotifers, and rainfall, which
helps drive the growth of the copepod nauplii. Other influ-
ences that help determine the proper stocking time include
day length, dissolved oxygen levels, and air temperature.
The research may improve the culture of additional tasty
fish species like yellow perch and walleye. If technology
affords consumers year-round choices from among several
cultured species, steady buying habits may develop. Then fish
farmers may not have their resources lying idle much of the
Ludwig and his colleagues are
also researching ways to manage
fish so they'll spawn all year long.
That means they need to develop the
know-how for providing a year's
supply of live, appropriately sized
zooplankton. Ludwig's plan also
calls for growing rotifers and cope-
pod nauplii in ponds or indoor tanks
and redesigning a device called a
rotating drum filter to harvest them.
Larger zooplankton will be freeze-
dried for enriching diets as the fry
grow into large fingerlings ready to
be moved into production tanks.-
By Ben Hardin, ARS.
This research is part ofAquacul-
ture, an ARS National Program
(#106) described on the World Wide
Web at http://www.nps.ars.
programs/appvs. htm.
Gerald M. Ludwig is at the Harry
K. Dupree Stuttgart National Aqua-
culture Research Center, USDA-
ARS National Aquaculture Research
Center, 2955 Hwy. 130 E., Stuttgart,
ture Research Center in AR 72160; phone (870) 673-4483,
gist Gerald Ludwig fax (870) 673-7710, e-mail snarc_
ine bass. *

Agricultural Research/February 2000



$ '..I
- 1


Bison and elk are the remaimng reservoirs ot brucellosis in the United states. RB51, the new vaccine that protects bison from the disease,
will be evaluated for protection of elk (shown above).

Microbiologist Diana
Whipple (left) and
animal caretaker Katy
Lies offer treats to a
white-tailed deer being
used to study tubercu-
losis in its wild

18 Agricultural Research/February 2000

Z oonoses-animal diseases that
are naturally communicable to
humans-have inflicted health
problems on millions of people
worldwide. But the power of three
devastating zoonotic diseases-brucel-
losis, leptospirosis, and tuberculosis
(TB)-may someday be broken up by
new knowledge of how they are trans-
mitted from wildlife to domestic animals
to humans. Agricultural Research Serv-
ice researchers at the National Animal
Disease Center (NADC) in Ames, Iowa,
are gaining this knowledge.

Agricultural Research/February 2000

White-tailed deer in northeast Mich-
igan have recently been identified as a
wildlife reservoir of TB, which is caused
by Mycobacterium bovis. The bison is a
natural host for brucellosis. Lepto-
spirosis, also called Weil's Disease, is
transmitted to humans mainly through
direct contact with infected animals, but
it can also sicken humans via contam-
inated soil or water.
"Elk, deer, and bison threaten U.S.
brucellosis and tuberculosis eradication
efforts by presenting the opportunity for
reinfection," according to ARS veterinar-
ian Carole A. Bolin, leader of bacterial
disease research.
As USDA's chief scientific research
agency, ARS assists and advises other
USDA agencies working with zoonotic
diseases-the Animal and Plant Health
Inspection Service (APHIS) and the
Food Safety and Inspection Service
(FSIS)-and other federal agencies like
the Centers for Disease Control and Pre-
vention (CDC) in Atlanta, Georgia.

TB Transmission
Milk is pasteurized to safeguard hu-
mans from becoming infected with M.
bovis. The incidence of TB in cattle has
declined steadily since 1917 when the
state-federal eradication program was
begun. In 1992, however, there was a
resurgence of the disease. In addition,
tuberculosis in captive deer and elk was
recognized as a growing problem.
The presence of TB in wild white-
tailed deer in Michigan poses a serious
threat to the program to eradicate the
disease from domestic livestock. ARS
scientists have been conducting research
on TB in white-tailed deer to determine
how to control and one day eliminate it.
ARS microbiologist Diana Whipple
and ARS veterinarian Mitchell V. Palm-
er developed a method to experimental-
ly infect white-tailed deer with M. bo-
vis. This method has been used to study
the transmission of TB from experimen-
tally infected deer to noninfected deer
in research pens at NADC.

Their work has provided the first ani-
mal model to study TB transmission in
white-tailed deer. "White-tailed deer ex-
perimentally infected with M. bovis de-
veloped lesions similar to those found in
naturally infected deer," says Whipple.
In other studies, Whipple says NADC
researchers have identified a possible
route of transmission of M. bovis from
experimentally infected deer to other
animals. "We found M. bovis in deer sa-
liva and nasal and tonsil secretions.
Therefore a cow or another deer might
become infected with M. bovis by eat-
ing feed contaminated with these secre-
tions," says Whipple.
DNA fingerprints show that both wild
and captive deer in Michigan are infect-
ed with the identical strain of M. bovis
recovered from coyotes, raccoons, a bear,
and cattle.

Tracking Leptospirosis
From Michigan deer to a public body
of water in Springfield, Illinois, and in
remote areas of Nicaragua, ARS re-
searchers have tracked another bacterial
disease that plagues animals and humans.
Leptospirosis is caused by spiral-shaped
bacteria called spirochetes (SPY-row-
keets). Infected domestic animals and
wildlife harbor these bacteria, more than
200 of which can cause leptospirosis.
To complicate matters, some animal
species can be a host to several different
bacterial strains, although usually ani-
mals are infected with only one type at a
time. Humans can contract the disease,
which is treatable with antibiotics, from
urine if traces come in contact with the
membranes around their eyes and mouth.
An international expert on zoonotic
diseases, Carole Bolin traced the cause
of a human outbreak of leptospirosis in
Nicaragua to dogs. (See "Cracking the
Hard Cases," Agricultural Research,
June 1996, p. 4.)
In June 1998, Bolin was called by the
CDC to help investigate the cause of a
feverish illness in more than 100 U.S.
athletes who became ill after swimming

in Lake Springfield. The illness resem-
bled leptospirosis. NADC researchers
tested water samples from the lake and
isolates of bacteria from the patients.
They also surveyed the livestock and
wildlife residing near Lake Springfield.
Laboratory tests confirmed the presence
of pathogenic leptospires in the lake;
however, the scientists were not able to
identify the specific animal source.

New Vaccines
In cattle, leptospirosis causes abor-
tions, stillbirths, and reproductive inef-
ficiency. The NADC researchers have
studied this disease since 1987. Their
studies show that previous commercial
vaccines for cattle have not adequately
protected them against some types of
However, "a new vaccine, developed
by BioCore in Omaha, Nebraska, gives
100 percent protection to cattle. Use of
the vaccine blocks bacterial colonization
in the urinary and reproductive tracts of
the cattle," says Bolin. She and her
research team are gathering data to

support licensing of the commercial
This is not the first time NADC re-
searchers have supported and tested new
vaccines to protect cattle against zoonot-
ic diseases. ARS veterinarian Steven C.
Olsen continues to explore the use of
Brucella abortus strain RB51 in adult
"Brucellosis in bison is very similar
to brucellosis in cattle," says Olsen. He
and the research team of Mark G.
Stevens, Mitchell V. Palmer, Shirley M.
Halling, Betsy J. Bricker, and Norman
F. Cheville extensively tested RB51 for
cattle. Because of their efforts, RB51
was approved by the USDA as the offi-
cial vaccine to protect U.S. cattle against
brucellosis, which costs U.S. beef and
dairy producers nearly $30 million an-
nually. This was the first time in over 50
years that a new vaccine was approved
for brucellosis in cattle. RB51 replaced
strain 19, a vaccine that is essentially no
longer used.
Preliminary data suggest that the
RB51 vaccine also protects bison against


Veterinarian Carole olin prepares to inject a cow with the new vaccine tor bovine

brucellosis. A larger study of bison heifer
calves-now under way-should pro-
vide more conclusive data on the efficacy
of the RB51 vaccine for calves. The ani-
mals were vaccinated as calves and have
been growing up. Once they get preg-
nant, the bison will be challenged with a
virulent strain of B. abortus to evaluate
whether the RB51 vaccine protects them
against abortion or infection. This study,
begun in 1996, will not be concluded un-
til the spring of 2000.
To lay the groundwork for commer-
cial use of RB51 in bison, Olsen collab-
orated with scientists from the Wyoming
Game and Fish Department and APHIS
to evaluate the potential effect of the
vaccine on several nontarget species.
"RB51 did not cause visible signs of dis-
ease in birds, rodents, or other wild spe-
cies. What we know about using RB51
in bison calves is that the young animals
don't shed the vaccine strain; it persists
longer in their lymph nodes than it does
in adult cattle.
"By next spring, we may have enough
data to obtain a conditional approval for
using RB51 in bison calves," says Olsen.
Since 1996, commercial use of RB51 has
been only in calves-both bison and
cattle. The results of inoculating bison
calves with RB51 should pave the way
for considering its use in a program to
control bison brucellosis in Yellowstone
National Park. This decision will be
made by the National Park Service.-
By Linda McGraw, ARS.
This research is part of Animal
Health, an ARS National Program
(#103) described on the World Wide Web
All of the researchers mentioned in
this article are at the USDA-ARS Nation-
al Animal Disease Center, Bacterial Dis-
eases of Livestock Research Unit, 2300
N. Dayton Rd., Ames, IA 50010; phone
(515) 663-7325, fax (515) 663-7458, e-
mail cbolin
dwhipple @ nadc.ars. +

Agricultural Research/February 2000

he high produc- U n lll n LilLy II
tivity of U.S. ag-
riculture in the New
20th century was
powered by the
19th century's Industrial
Revolution and by the sci-
ences of genetics and organic chemistry. Now, as late 20th
century advances in molecular biology and information tech-
nology increase yields and use of renewable materials pro-
duced on farms, ARS scientists are focusing on making it all
happen in ways that minimize risks to our environment.
Just as in the past 50 years, petroleum engineers have im-
proved a process called catalysis-or fluidized catalytic crack-
ing-to nearly maximize the amount of energy obtainable from
a barrel of oil, agricultural scientists may develop biocatalysis
to efficiently convert farm commodities into a variety of use-
ful products.
Biocatalysis is the process of using enzymes in a laboratory
or factory to synthesize compounds. It's a "green"-environ-
mentally friendly-process because it may not require
petroleum-based solvents. And products made via biocatalysis
can themselves be made from renewable resources.
"This year we started researching biocatalysis as a way to
synthesize novel fats and oils," said Joe Laszlo, a lead scientist
in the Biomaterials Processing Research Unit at the National
Center for Agricultural Utilization Research in Peoria, Illinois.
So far, NCAUR chemist Dave Compton and Laszlo have used
an enzyme to construct an ultraviolet light-absorbing sunscreen
made from any of several vegetable oils and other natural plant
Now Compton and Laszlo are teaming up with Jerry King,
a chemist who leads the NCAUR's Food Quality and Safety
Research Unit. The scientists are moving the research to a
laboratory especially designed for processing larger amounts
of vegetable oils at higher pressures and temperatures. In the
larger setup, they are using supercritical carbon dioxide as a
solvent for reacting and extracting compounds synthesized by
the enzymes.
In other research, King and his colleagues developed a two-
step process using supercritical carbon dioxide, hydrogen,
methanol, and an enzyme and another catalyst to convert soy-
bean oil into hydrogen-saturated alcohol mixtures. Such mix-
tures are used to make soaps, detergents, and related chemicals.
"With supercritical fluid extraction, we compress and heat
a gas-usually carbon dioxide-so it becomes more dense and
liquidlike," King explains. In this unique physical and chem-
ical state, the carbon dioxide can pass through a mixture and
dissolve specific fats or other materials. The gas is then de-
compressed and harmlessly vented into the atmosphere, leav-
ing the extracted products behind. -By Ben Hardin, ARS.

This research is part of
New Uses, Quality, and
Marketability ofPlant and
Animal Products, an ARS
National Program (#306)
described on the World
Wide Web at http://www.

nps. ars.
David L. Compton, Joseph A. Laszlo, and Jerry W King are
at the USDA-ARS National Center for Agricultural Utilization
Research, 1815 N. University St., Peoria, IL 61604; phone
Compton (309) 681-6321, Laszlo (309) 681-6322, King (309)
681-6203, fax (309) 681-6685, e-mail comptond@mail.ncaur, laszloja @mail.ncaur, kingjw@mail.ncaur. *


Chemist Dave Compton adjusts the pressure-control gauge on a
device while a biocatalysis reaction occurs inside. He is optimizing
procedures for making an all-natural soy-based sunscreen.

Agricultural Research/February 2000


i E n r T'^ I L

6i LU IUUuC;


~B~C1~IIIPCPs b ~- I-a

ver wivnder :to. insects find
exactly what plant they wantt to bat?
Entomologist Joseph C, Dickens has
found the answer to that, question-at
least for one key potato pest/Because of
his inquisitiveriess about olorado pota-
to beetles. there's good news for grow-
ers: An attractant may not be far away.
For at least 73 years, scientists have
been searching for a scent that attracts
this yellow and black hug to solanaceous
plants. Colorado potato beetles are the
potato crop's most destructive insect
pest, costing growers millions in chem-
ical control and crop losses each ear.
By placing tiny electrodes on the tips
of their antennae and monitoring their
sensitivity. Dickens. who is \ ith ARS'
Vegetable Laboratory in Belts\ille.
Maryland, discovered several chemical
scents that attract the pests. He exposed
the insects to different potato leaf aro-
mas and allowed them to choose those
they preferred.
When Dickens offered the beetles a
choice between one of the attractive
scents and potato foliage, the beetles
wereterriblb confused. he says, and the\
eventually responded randomly.
"We separated odors from both nor-
mal and wounded plants using a gas
chromatograph, which separates chem-
ical mixtures into components," says
Dickens. This allowed us to stimulate
the beetles' antennae with the individu-
al components to see which they could
smell. We monitored the insects' re-
sponses to both real and synthetic scents.

SSo far, We've tested 16 different synthet-
ic chemical blends, and we hope to de-
velop and test more."
During summer 1998. Dickens was
surprised to find in a preliminary field
test that the beetles were captured with
a synthetic lure containing a mixture of
a few of these compounds. He says no
one had ever caught a Colorado potato
beetle with a synthetic lure before. He
and his colleagues ha\e identified at
least five different synthetic blends that
are attractive to the insects in laborato-
ry tests and ma\ work in the field as
"From this research, naturally occur-
ring chemical signals could be used to
monitor and control pest populations."
Dickens sa\s.
He is also investigating how% chemi-
cal scents. w which are emitted when the
beetles chew on plants. might help at-
tract potato beetle predators. Two pred-
ators of interest are spined soldier bugs
and two-spotted stink bugs. Dickens has
already identified chemical blends that
arc attractive to both.
Down the road, these chemical
blends could be used as part of a blo-
logical control effort using natural ene-
mies to control Colorado potato beetles.
thus reducing reliance on pesticides.
Growers frequently apply insecti-
cides to control the critter, but it has
armed itself with resistance to many
chemicals. "Our ultimate goal," says
Dickens, "is to develop a synthetic at-
tractant to combine with a toxin or

pathogen in a bait, which could be used
to control this pest."-By Tara Weaver-
lissick. ARS.
This research is part f Crop and Com-
modity Pest Biology Control, and Quar-
antine (#3(04), an .RS National Program
described on the lorld i'ide i b at http:/
Joseph C. Dickens is at the USDA -ARS
Vegetable Laboratory. Bldg. 010.4, Room
112, 10300 Baltimore .Ae., Beltsville. ID
20705-5374: phone (301) 504-8957, fa
i301 504-5555, e-mail jdickens '
arsisdai. go.: *

A gas cnromatograpn trw,) is useu ut
identify individual scents emitted from
potato foliage. Above, entomologist Joseph
Dickens positions a Colorado potato beetle
antenna in front of a GC outlet to find out
which scents the insect detects.

Agricultural Research/February 2000

Gene May Stall Fall
A gene that directs plants to produce a
protein that seems to help keep fall ar-
myworm larvae from developing into
crop-eating caterpillars has been found
and isolated. Now, the world's largest
vegetable seed company, Seminis, has
signed an agreement to investigate the
potential use of the gene to control a va-
riety of caterpillars in broccoli, cauliflow-
er, and other vegetables. This could help
commercial growers lower the cost of
pesticide inputs. Researchers isolated the
protein, a cysteine proteinase, from cul-
tured tissue of resistant corn plants and
obtained a patent last November for the
gene sequence that encodes it. The sci-
entists evaluated corn hybrids with both
natural and bioengineered resistance to
fall armyworms in collaboration with
DeKalb Genetics Corp. of DeKalb, Illi-
nois. In lab and field tests, they evaluat-
ed hybrids developed by DeKalb using
germplasm created and released by ARS
as a source of natural resistance. W Paul
Williams, USDA-ARS Crop Science Re-
search Laboratory, Mississippi State,
Mississippi; phone (601) 325-2735, e-

Developing Foods That Pro-
mote Health-A Report
A new report could help scientists in the
health, nutrition, and plant sciences
sharpen their focus on developing health-
enhancing foods. Several of the more
than 100,000 secondary compounds
made by plants may play a role in
reducing chronic or degenerative diseases
in people. Lycopene in tomatoes,
sulforphane in broccoli, and genistein in
soybeans are a few of the so-called phyto-
nutrients that have captured headlines.
But before plant scientists beef up phyto-
nutrients in fruits and vegetables, they
need to know which compounds are most
beneficial and whether they work alone
or synergistically-as evidence suggests
they often do. To give plant scientists de-
finitive answers, nutrition and health

scientists need better tools to measure
phytonutrients' efficacy in reducing
disease risk. These needs-along with
the state of phytonutrient science-are
discussed in a new 56-page report titled
"Forum and Workshop on Food, Phyto-
nutrients, and Health." It is the pro-
ceedings of a 1998 workshop sponsored
by ARS for plant and nutrition scientists,
food technologists, and immunologists,
to stimulate collaboration among the
disciplines. The report can be ordered
from Allen Press for $35 (includes ship-
ping and handling): phone (800) 627-
0629, fax (785) 843-1274, e-mail Kathleen C.
Ellwood, ARS National Program Staff,
Beltsville, Maryland; phone (301) 504-
4675, e-mail

Blueberry Elixir Reverses
Age-Related Symptoms
A diet rich in blueberry extract has
reversed some loss of balance and
coordination and improved short-term
memory in aging rats. This is the first
study to show fruits and vegetables
actually reversing dysfunctions in behav-
ior and in nerve cells. Earlier, the res-
earchers reported that high-antioxidant
fruits and vegetables prevented some loss
of function in aging rats. Blueberries,
strawberries, and spinach test high in
their ability to subdue oxygen free
radicals that can damage cell membranes,
DNA, and other delicate internal mach-
inery. Many of the dysfunctions and
diseases associated with aging are
blamed on oxygen free radicals. Daily for
8 weeks, researchers fed extracts of
blueberry, strawberry, or spinach to 19-
month-old rats-the age-equivalent of
65- to 70-year-old humans. All three
improved short-term memory, but only
the blueberry extract improved balance
and coordination. Since motor behavior
is one of the first things to go with aging,
the improvements in coordination and
balance are really significant; little else
reversed these deficits in motor function.
If this finding holds for humans, it should

further encourage consumption of fruits
and vegetables high in antioxidants.
James A. Joseph and Barbara Shukitt-
Hale, USDA-ARS Human Nutrition
Research Center on Aging at Tufts
University, Boston, Massachusetts;
phone (617) 556-3178 [Joseph], (617)
556-3118 [Shukitt-Hale], e-mail
joseph_ne @ hnrc. tufts. edu or hale_ne @

Homes Opened for Arctic-
and Arid-Land Plants
Two new sites for conserving and man-
aging plants important to U.S. agricul-
ture are now open in Palmer, Alaska, and
Parlier, California. The new sites join 26
others in ARS' National Plant Germ-
plasm System that store more than
434,000 specimens of seeds and other
genetic materials of crops and their wild
relatives. Researchers use these germ-
plasm materials to identify useful traits
for breeding into commercial varieties.
For long-term germplasm storage, it's
crucial to grow the plants periodically
to regenerate the seed or other reproduc-
tive tissue. Naturally, the plants grow
best and produce the most seed in their
native areas. The National Arctic Germ-
plasm Site at Palmer offers a growing
site for northern grasses and crops-
some grains, legumes, and vegetables-
that grow in high elevations or above 60
degrees north latitude. At the Arid-Land
Plant Germplasm Regeneration and Ge-
netic Resource Unit in Parlier, plants
enjoy hot, dry summers and about 14
inches of rain per year. This site serves
as an alternate location for other gene-
banks to grow out crops that benefit from
a long, frost-free season or that prefer a
dry area. David M. lanson, Curator,
USDA-ARS NationalArctic Germplasm
Site, Palmer Alaska; phone (907) 745-
4469, e-mail davidianson@ dnr. state. Maria M. Jenderek, Curator,
USDA-ARSArid-Land Plant Germplasm
Regeneration and Genetic Resource
Unit, Parlier California; phone (559)
646-0307, e-mail

Agricultural Research/February 2000

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