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Agricultural Research Service.
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With wide acceptance of the view that
upland agriculture can affect downstream
marine environments, Agricultural Re-
search Service scientists are increasingly
turning their attention to coastal marine
waters. They are particularly concerned
about the potential effects of nutrients
from agriculture and other sources on the
water quality of coastal estuaries such as
the Chesapeake Bay.
Livestock manure and fertilizers are
excellent sources of essential plant nutri-
ents, including nitrogen and phosphorus.
However, excessive application may re-
sult in runoffinto waterways and ultimate-
ly into coastal waters, where they can
stimulate "blooms" of undesirable algae.
Harmful algal blooms and red tides of
microscopic dinoflagellates, along with
Pfiesteria outbreaks, are becoming an
increasingly serious problem around the
world, threatening natural fisheries,
aquaculture, and human health.
Closer to home, they have caused major
fish kills and human health problems in
the Chesapeake Bay and Atlantic coastal
waters. Excessive growth of algae and
aquatic plants in the Gulf of Mexico has
resulted in a lifeless area known as the
"Dead Zone," created when decompos-
ing plants rob the waters of life-sustain-
While it has not been clearly estab-
lished that agricultural nutrients are re-
sponsible for these phenomena, there is
scientific consensus that they can be an
important contributing factor. Clearly we
need to understand the relationship be-
tween agriculture and coastal water qual-
ity, reduce nutrient levels in livestock
manure, and minimize nutrient losses to
water and air from fertilizer and during
manure handling, storage, and field ap-
This is particularly important for areas
near the Chesapeake, the Nation's pre-
mier, but threatened, estuary. Agricul-
ture should, and can, be compatible with
a healthy Chesapeake Bay.
USDA in general, and ARS in partic-
ular, are well positioned to carry out fo-
cused research programs whose goal is
to better understand and minimize nega-
tive impacts of agriculture on coastal
environments. ARS currently supports 35
research projects related to effective
management of fertilizer and manure
nutrients to enhance crop production and
protect environmental quality.
Two leading laboratories in this re-
search are the Environmental Chemistry
Laboratory in Beltsville, Maryland, and
the Pasture Systems and Watershed
Management Research Laboratory in
University Park, Pennsylvania. Scientists
in those labs have developed nutrient
management practices for more effective
use of nitrogen and phosphorus from
fertilizer and manure, gained an under-
standing of air and water transport of
pesticides to the bay, and evaluated the
effectiveness of riparian buffers for wa-
ter quality protection.
ARS has recently stepped up its re-
search related to agriculture and coastal
environments. Highlights include:
Examining, in a new program in-
volving six Beltsville labs, the fate and
effect of pathogens, parasites, and nutri-
ents in manure that is land-applied, com-
posted, or otherwise treated.
Increasing the efficiency of phos-
phorus use by monogastric (one-stom-
ach) animals through phytase enzyme
feed additives and developing low-phy-
tic-acid feed grains, to lessen excretion
of unused phosphorus in manure.
Assessing the effectiveness of ripar-
ian zones, vegetative buffers, and wet-
lands for nutrient removal.
Developing poultry litter treatment
(alum) that protects environmental qual-
ity by reducing ammonia emissions and
Using algae as giant water filters to
remove nitrogen and phosphorus from
liquid manure from dairy barns.
Seeking a better understanding of
factors that trigger blooms of harmful
algae, Pfiesteria, and related microbes.
Developing special antibody probes
to detect and identify Pfiesteria-like or-
ganisms and their toxins and explaining
their effects on fish. In 1997, ARS and
the University of Maryland co-sponsored
a workshop to develop strategies to ap-
ply molecular technologies to Pfiesteria
Documenting that oysters can har-
bor Cryptosporidium parvum, a danger-
ous protozoan parasite-the first time it
has been found in a marine organism eaten
by people. C. parvum is shed in the waste
of livestock, wildlife, and humans.
Using hydroponically grown fruits
and vegetables to clean nutrients from
fish wastes in aquaculture operations.
Just as water quality is important to
natural environments and commercial
fisheries, it is vital for successful aqua-
culture. A toxic algal bloom can wipe out
a fish farm overnight. Aquaculture is an
$800 million to $1 billion business in the
United States-and growing.
ARS' expanding aquaculture program
includes work in Delaware, West Virgin-
ia, Alabama, Arkansas, Louisiana, Mis-
sissippi, and Hawaii. It addresses water
quality and environmental compatibility;
fish health, growth, nutrition, reproduc-
tion, genetics, and production systems;
and aquaculture food safety and quality.
Expertise in aquaculture can be directly
applied to research on agriculture's im-
pact on water quality and fisheries.
Henry S. Parker, ARS National
Program Leader for Aquaculture
Robert J. Wright, ARS National
Program Leader for Soil Management
Agricultural Research/January 1999
Vol. 47, No.1
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
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 http://www.ars.usda.gov/is/AR/.
Subscription requests should be placed with New
Orders, Superintendent of Documents, P.O. Box
371954, Pittsburgh, PA 15250-7954. See back
cover for order form.
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
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.
Protecting the Chesapeake Bay 4
Baiting and Trapping Orchard Pests 9
Storing Pecans Longer, Better 9
Long-Term Effects of Low Birth Weight 10
Batter Up! 11
Better Diets for Delta Residents 12
Summer Program REAPS Lasting Benefits 14
Safer Salad Is "In the Bag" 16
Software To Improve Food Safety 17
Barberpole Worms-Parasites of Another Stripe 18
Making Coccidia Less Cocky 20
Low-Cost Way To Pave Feedlots 22
"Star Wars" Technology for a Down-to-Earth Problem 23
Winterfat Seeds Take Ice Stakes Through the Heart 24
Deep-Tank Fermentation for Cheaper Bioinsecticides 25
Arabidopsis: A Model Plant Genome 26
Science Update 27
Cover: Agricultural Research Service scientists are looking hard at possible links
between agricultural practices and problems in marine environments such as the
Chesapeake Bay. Many rivers empty into this 200-mile-long inlet of the Atlantic
Ocean. Photo by Scott Bauer. (K8301-1)
In the next issue!
Experiments set up in 1931 have helped chronicle the history of
farming on the upper Northwest's Columbia Plateau. Now they give
Agricultural Research Service scientists a baseline for identifying
sustainable farming practices.
The National Food Safety Initiative began in 1997 to improve the
safety of food all the way from where it starts ... on the farm ... to
where it winds up ... on your table.
1 Why would anyone want to draw a map of the soybean's genetic
layout? One reason is a projected extra 220 million bushels of soy-
beans a year for American farmers, if the map yields a way to thwart
just one pest-the soybean cyst nematode.
Agricultural Research/January 1999
Protecting the Chesapeake Bay
We tend to think of runoff
water as the source of pol-
lutants in rivers, lakes, and
While that is largely true,
runoff is not the only source of pollution.
Pesticides, nitrogen, heavy metals, and
toxic compounds are literally falling from
the sky into the Chesapeake Bay and other
bodies of water around the world.
Scientists with the Agricultural Re-
search Service are documenting when,
how, and how much nitrogen, pesticides,
and other agricultural compounds reach
the bay. If they find amounts to be ex-
cessive, their aim is to reduce the atmos-
pheric entry of these agriculturally based
compounds in the future.
The bay's watershed-all the land that
drains into it-is 64,000 square miles,
including all or part of six states, from
New York to southern Virginia.
The U.S. Environmental Protection
Agency (EPA) has a similar word-air-
shed-to describe the air source of a
pollutant that falls onto the ground or
water as gases or dry particles or is at-
tached to water molecules in precipita-
tion or fog.
An airshed is the air above a water-
shed-and then some. Unlike a water-
shed, an airshed has no physical
boundaries. Its borders depend mainly on
how far a specific airborne pollutant may
travel. EPA has thus far mapped out an
airshed only for nitrogen oxide emissions.
The bay's airshed for these-mostly from
autos and power plants-covers 350,000
square miles. It includes the air above all
or parts of 13 states plus Ontario, Que-
bec, and all of lakes Ontario and Erie.
The bay's nitrogen oxide airshed extends
west to Michigan and south to South
It is possible that the airshed for some
chemicals reaching the bay may include
Wetland and streamside vegetation serves
as a buffer to filter excess nutrients from
water running off agricultural land. Photo
by Scott Bauer. (K8307-9)
the entire eastern United States. But the
bay airshed is defined as the air from
which 70 percent of a particular airborne
chemical would drop on the bay or its
Ammonia by Air
As its next airshed map, EPA is con-
sidering ammonia gas. ARS scientists
suspect the bay's airshed is smaller for
Chemists Laura McConnell (right) and
Jennifer Harman-Fetcho work with Uni-
versity of Maryland scientists to improve
water quality and the overall productivity
of the Horn Point oyster hatchery.
ammonia than fornitrogen oxides because
ammonia seems to travel much shorter
"But we don't really know how far
ammonia travels or how much of a prob-
lem it is," says ARS soil scientist John J.
Meisinger. "It might go a half mile, or
maybe 5 to 10 miles."
Meisinger studies ammonia gas escap-
ing from poultry manure on Maryland's
Eastern Shore, as well as from dairy
manure at ARS' Beltsville (Maryland)
Agricultural Research Center. He says
poultry manure seems to give off less
ammonia than previously thought.
He uses small wind tunnels and micro-
meteorology techniques to monitor am-
monia losses from manure placed on
fields. Meisinger is with the ARS Envi-
ronmental Chemistry Laboratory in Belts-
ville. This lab, along with ARS' Pasture
Systems and Watershed Management Re-
search Laboratory in University Park,
Pennsylvania, develops farm practices
that protect the environment and food
supply, with emphasis on the Chesapeake
Phillip A. Moore, Jr., an ARS soil sci-
entist in Fayettville, Arkansas, has found
that ammonia loss is reduced if alum is
mixed with poultry litter in the chicken
houses. Poultry litter is a mix of bedding
Alum, or aluminum sulfate, is a mild
acid that lowers the pH of litter, reducing
ammonia volatilization in the chicken
house and when the litter is applied to the
"If I had to pick a single solution for its
potential to reduce both the problems of
ammonia emissions to the air and phos-
phorus losses in runoff, I would place my
money on alum for the short run," Meis-
inger says. Alum also changes the phos-
phorus in the litter to a form that is less
soluble in water. [See "Managing Poul-
try Manure Nutrients," Agricultural Re-
search, June 1998, p. 12; "A Cleanup for
Poultry Litter," May 1994, p. 10.]
But Meisinger warns that alum is only
a short-term solution. "Ultimately you
have to find a way for chickens to use
more of the nitrogen and phosphorus in
the feed," he says.
Phosphorus by Land
Another soil scientist, Eton E. Cod-
ling, who is also at the Environmental
Chemistry Laboratory, is investigating
the effects of mixing alum residue from
a drinking water treatment plant into
chicken litter before applying it to corn-
fields at two farms on the Eastern Shore.
The residue contains trace elements-
particularly iron-removed from the
drinking water by alum and lime.
Agricultural Research/January 1999
Donald Merrit, a research biologist for the University of Maryland's Horn Point Center for Environmental Studies, pilots a boat from which
ARS chemists Laura McConnell (left) and Jennifer Harman-Fetcho collect samples of oysters, water, and sediment from the Choptank
River on Maryland's Eastern Shore.
Codling chose the farms after conduct-
ing a survey in 1997 of 10 Eastern Shore
farms that have applied chicken litter to
their fields for more than 25 years. He
found that nine of the farms had high
phosphorus levels and chose two of them
for the alum residue study.
Phosphorus has gotten more attention
recently because of its possible role in
fueling toxic blooms of the microbe Pfies-
teriapiscicida in bay tributaries and oth-
er rivers on the East Coast.
Tom Simpson with the Maryland De-
partment of Agriculture says he can find
no agricultural trend to account for the
Pfiesteria problem, other than rising
phosphorus levels in soils. In the three
counties that make up Maryland's lower
Eastern Shore, phosphorus levels have
risen steadily since about 1956.
A recent survey found levels in many
soils to be three to six times higher than
the maximum amount crops can use.
Simpson stresses that no one has yet
Oysters collected from the Choptank
River by chemists Laura McConnell (left)
and Jennifer Harman-Fetcho will be
analyzed for agricultural chemicals.
proven a Pfiesteria-phosphorus connec-
tion. Even so, algal blooms and oxygen
depletion in the bay have a major eco-
nomic impact on the region.
Maryland has long had a voluntary
nutrient management program. But be-
cause of the Pfiesteria outbreak, the state
is phasing in a mandatory program over
the next 4 to 7 years. The program-the
strictest in the country-targets phospho-
rus and nitrogen. Simpson says new poul-
try manure recommendations for a typical
farm with high-phosphorus soils will be
cut from 3 to 4 tons an acre to a half ton
or less. Meisinger says these steep cuts
should reduce losses of both phosphorus
and nitrogen to the bay, but lower appli-
cation rates will require more acres to
spread the manure on and higher trans-
portation costs to carry it farther away.
Says Simpson, "We have long depend-
ed on ARS research, in collaboration with
the University of Maryland and other
Agricultural Research/January 1999
work with nitrogen and Andrew Sharp-
ley's work with phosphorus. Sharpley is
the world's number-one authority on
phosphorus in runoff water. He did the
pioneering work back in the 1980s. We
depended on his work to help us recog-
nize that runoff was carrying high levels
of dissolved phosphorus."
Sharpley is a soil scientist at ARS'
University Park lab, where a variety of
studies important to the Chesapeake Bay
are under way. Included is work on the
effect of agriculture on nitrogen and phos-
phorus cycling, losses from intensively
grazed pastures, and the role of wetlands
and streambank vegetation in removing
nitrogen from agricultural runoff.
Sharpley says that the only permanent
solution to reducing soil phosphorus or
nitrogen levels "is to balance farm input
and output. In other words, producers
should attempt to reduce the amount of
phosphorus and nitrogen brought onto a
farm as feed and fertilizer. They should
supplement fertilizer use with onfarm
manure where available," he says, "so
that crops and animals are fed as closely
as possible the phosphorus and nitrogen
they actually need."
He says this is especially important in
parts of a watershed particularly vulner-
able to runoff. "Generally, most of the
phosphorus running off watersheds
comes from only a small area of the land
during a few large storms."
Sharpley and others helped USDA's
Natural Resources Conservation Service
(NRCS) develop a simple index to pin-
point and rank the sources of phospho-
rus-the so-called hot spots.
Farmers whose soils have a low risk
ranking would be advised to test the soil
every 3 years and recommended to "keep
up the good work and think before you
make changes that could raise soil phos-
Farmers with fields that have a medi-
um risk should implement practices to
reduce phosphorus losses, such as using
less tillage, so as to cut run-
off and soil erosion. Those
fields with a high risk for
phosphorus loss should re-
ceive phosphorous fertiliz-
er or manure only sparingly
Farmers whose soils have ave r\
high risk ranking would be .d-
vised to consider a more compre-
hensive test and to not applI
phosphorous fertilizer or m,nure for
at least 3 years.
Sharpley was recently appointed to
coordinate ARS' contribution to a niie
national program with NRCS. uni\ er I-
ties, and EPA to assign phosphorus
thresholds for a wide range tf soil i pe,
across the United States by 2(012.
Pesticides by Air and by Sea
Beltsville chemist Laura L. lNcCon-
nell has spent several years sanmplin in-
tensively for pesticides in wjtei. air. aid
rain. Her biggest airshed expert nel I is.
a 3-year cooperative project at ihe mouth
of the Patuxent River with the Li n \ eri i\
of Maryland's Chesapeake Biological
Laboratory at Solomons. She has consis-
tently found pesticides in water, air, and
rain, but only in concentrations well be-
low EPA's health advisory levels for
drinking water. For example, the agri-
cultural herbicide atrazine shows up at
levels of 0.4 parts per million (ppm) in
some tributaries of the bay-amounts far
less than the EPA drinking water guide-
line of 3 ppm.
McConnell has documented the con-
tinuing global air transport of old as well
as new pesticides-including some that
were banned years ago, such as DDT and
toxaphene. She found these pesticides in
the waters of the world's deepest lake,
Siberia's Lake Baikal. Her work relies
heavily on the findings of another ARS
colleague, chemist Clifford P. Rice, who
did the earliest studies of atmospheric
transport of pesticides.
McConnell also collaborates with
Steven J. Lehotay, Rice, and others in a
SCOTT BAUER (K8305-8)
Agricultural Research/January 1999
Soil scientist Eton Codling notes excellent corn growth on manured soil treated with alum
residue, which cuts ammonia emissions to the air and phosphorus losses in runoff water.
study of oysters. This project is part of
the National Oceanic and Atmospheric
Administration's (NOAA) Mussel Watch
program. It has been expanded to moni-
tor oysters for newer pesticides. So far,
no herbicides have been found. But the
insecticide endosulfan has shown up con-
sistently enough to prompt a closer look
for it in waters of the Chesapeake Bay
and other sites around the country by the
Mussel Watch program.
One Fix: Reduce or Filter Runoff
Soil scientist Gregory W. McCarty,
with the Environmental Chemistry lab,
has finished his first year of a study to see
how well a wetland can filter chemicals
from farm runoff before the pollutants
reach a bay tributary. The wooded,
swampy wetland at the ARS Beltsville
center receives runoff and groundwater
from an adjoining field planted to corn
this year. McCarty must often don wad-
ing boots and walk carefully across wet-
land muck to collect samples. In most
places, a hidden mat of tree roots holds
up the muck-and McCarty. He also sam-
ples water below the field, as well as
below and in a nearby stream.
He found the test site has a complex
natural plumbing system-including
countless leaks that seem to weaken the
wetland's filtering role. Some ground-
water below the field flows directly into
the stream through "holes" formed in the
streambank by hydrostatic pressure.
The test results make McCarty doubt
that this particular wetland protects the
stream from nitrate-a form of nitrogen.
He found that groundwater pouring into
the stream is extremely clean, except for
high levels of nitrates.
McCarty is also testing eastern gama-
grass as a buffer strip at the edge of the
field to filter out excess nutrients before
they reach the swamp.
At experimental tomato fields in Belts-
ville, McCarty is checking runoff for ni-
trate and phosphorus. The tomatoes are
grown by two contrasting methods. In the
standard method, tomato seedlings are
planted through sheets of black plastic
mulch, a method widely used on Mary-
land's Eastern Shore. The alternative
method uses hairy vetch residue as an
Chemist Cathleen J. Hapeman, who
leads the Environmental Chemistry lab,
and Pamela J. Rice, an ARS chemist and
toxicologist, head up the tomato runoff
project. Their data show that the plastic
sheets allowed 10 times more runoff than
vetch after the first storm of the 1997
tomato season-and twice as much in the
following dozen storms. They are cur-
rently analyzing 2 years of data for pes-
ticide and nutrient levels.
McCarty says the higher sediment
amounts in runoff from the plastic-
mulched areas point to a higher phospho-
rus load-since phosphorus tends to cling
By themselves, none of these studies
can answer questions about the actual
toxicity of this runoff to bay organisms.
To help find answers, Paul Hetzer is test-
ing runoff from the Beltsville plots on
bay creatures such as grass shrimp, clams,
oysters, and sheepshead minnows at the
Chesapeake Biological Laboratory.
Hetzer is a graduate student at the Uni-
versity of Maryland at College Park.
Clifford Rice and Ed Johnson, former-
ly with ARS and now with NOAA, have
monitored several artificial wetlands on
the Eastern Shore for effectiveness in
removing pesticides from runoff before
they reach bay tributaries. They are work-
ing with NRCS and the Smithsonian In-
stitution's Environmental Research
So far, they have found the wetlands
are doing an excellent job, especially
during major rainstorms. For example,
the amount of herbicides removed from
runoff by two artificial wetlands in Kent
County, Maryland, ranged from 83 per-
cent for simazine to 95 percent for gly-
Walter Mulbry, a microbiologist at the
ARS Soil Microbial Systems Laboratory
in Beltsville, is testing a very different
type of artificial wetland-algae in tanks
or long raceways-for effectiveness in
removing nitrogen and phosphorus from
dairy manure. These homegrown algae
could be used as animal feed or as green
manure for fields. Mulbry points out that
since the algae are harvested often, they
might have an insatiable appetite for nu-
trients-unlike the other kind of wetlands,
which get filled up on the pollutants.
By land or by air, ARS scientists are
determined to trace agriculture's possi-
ble role in Chesapeake Bay problems-
and find solutions.-By Don Comis,
Cathleen J. Hapeman and other sci-
entists in the USDA-ARS Environmental
Chemistry Laboratory can be reached at
Bldg. 001, BARC-W, 10300 Baltimore
Ave., Beltsville, MD 20705-2350; phone
(301) 504-6511, fax (301) 504-5048,
e-mail chapman @ asrr.arsusda.gov.
Andrew W. Sharpley is at the USDA-
ARS Regional Pasture Systems and Wa-
tershed Management Research Labora-
tory, Curtin Rd., University Park, PA
16802; phone (814) 863-0948, fax (8140
865-2058, e-mail email@example.com. *
Agricultural Research/January 1999
Baiting and Trapping Orchard Pests
Stink bugs, those flying pecan orchard pests, are finicky
eaters. And while they prefer to munch on the pecan variety
Desirable more than Stuart, they will feed on many kinds of
pecans. But no matter which nut this bug favors, farmers prefer
to keep them grounded.
Entomologist Michael T. Smith, working closely with both
the Jenkins and Horton orchards, has developed a strategy for
keeping stink bugs out of the air. Formerly in ARS' Southern
Insect Management Research Unit at Stoneville, Mississippi,
Smith says pecan growers may control stink bugs entering pe-
can orchards-and even reduce their feeding damage to trees
adjoining crops such as soybeans-by planting and spraying
within a trap crop.
The bait: a strip planted along orchard borders of a favorite
bug-munchie such as speckled purple hull pea, an edible delight
to stink bugs. This pea variety produces pods continuously over
"It's like building a moat around a castle," says Smith, who
is now with ARS' Beneficial Insects Introduction Research
Laboratory in Newark, Delaware. "The bugs stop at the trap
crop to dine and don't make it to the farmer's money-making
Stink bugs, the most damaging pests in Mississippi pecan
orchards, take flight into the orchards before and during soy-
bean harvest. But they continue to enter orchards from August
through pecan harvest, which may extend into November and
Stink bug feeding causes two types of pecan damage: black
pit and kernel spot.
When the bug pierces the nut with its needlelike nose before
shell hardening, it spews a chemical on the kernel, causing it to
turn black and cease development, resulting in black pit. If the
pest feeds after shell hardening, the result is kernel spot. Here,
stink bugs drill through the hardened shell, "spit" on the kernel
to make it soft, and suck the meat out, leaving a black spot on
Trap cropping could greatly reduce this pecan damage. It
concentrates the bugs in an area outside the orchard, so farmers
can control them economically with insecticides. This reduces
broad insecticide spraying and increases grower profits.
Reduced pesticide spraying also means less impact on the
environment and beneficial insects. Most insecticides used to
control stink bugs also kill the beneficial insects that control
In a recent field study, Smith found feeding damage within
the trap-crop-protected area was about 50 percent lower than in
the unprotected area.-By Tara Weaver, ARS.
Michael T. Smith is at the USDA-ARS Beneficial Insects
Introduction Research Laboratory, 501 South Chapel St., New-
ark, DE 19713; phone (302) 731-7330, ext. 41, fax (302) 737-
6780, e-mail firstname.lastname@example.org. *
Storing Pecans Longer, Better
If you had pecan pie on your Thanksgiving menu, it could
have been made with pecans that had been stored for about 10
to 12 months. And nuts stored that long can rapidly become
stale unless kept frozen.
But ARS research horticulturists Elizabeth A. Baldwin and
Bruce W. Wood have teamed up to extend the shelf life of
pecans. Baldwin has developed an edible coating that keeps
pecans stored for 10 months at room temperature from becom-
At the ARS Citrus and Subtropical Products Laboratory in
Winter Haven, Florida, Baldwin used three different coatings
made from cellulose that kept the nuts tasting good.
"Cellulose, the most abundant polysaccharide found in na-
ture, is an all-natural product. It is commercially available and
relatively inexpensive," she says. "It would be easy for a proc-
essor to spray these coatings on the nutmeats."
According to Baldwin, the experimental coatings are made
from three types of cellulose: methyl, hydroxy propyl, and
carboxy methyl. "Carboxy methyl cellulose (CMC) turned out
to be the best preserver of flavor. It also gave the pecans a high
gloss, improving their appearance.
"Although the CMC coating imparted a shine, the nuts didn't
look or feel oily," says Baldwin. "And their color was not as
dark as the control, or untreated, nuts. The color is a potentially
important factor because consumers associate dark-colored
pecans with rancidity, a condition when oxygen enters the nut
and breaks down, or oxidizes, some of its fat."
The coatings, which are generally recognized as safe by the
U.S. Food and Drug Administration, would need to be listed on
the label as an ingredient.
Wood, who heads the ARS Southeastern Fruit and Tree Nut
Research Laboratory in Byron, Georgia, collaborates with
Baldwin on the project.
"The pecan industry is interested in further developing the
coatings, which could promote year-round consumption," he
says.-By Doris Stanley, ARS.
Elizabeth A. Baldwin is at the USDA-ARS Citrus and Sub-
tropical Products Research Laboratory, P.O. Box 1909, Win-
ter Haven, FL 33880; phone (941) 293-4133, ext 119,fax (941)
299-8678, e-mail email@example.com.
Bruce W. Wood is at the USDA-ARS Southeastern Fruit and
Tree Nut Research Laboratory, 21 Dunbar Rd., Byron, GA
31008; phone (912) 956-6421, fax (912) 956-2929, e-mail
Agricultural Research/January 1999
Long-Term Effects of Low Birth Weight
Small infants may have a
greater risk of developing
heart disease or diabetes
later in life.
gests that poor nutrition in the
womb might have lifelong con-
sequences for health. The results
of the study could be important
for many in the United States, as well as
Nutritionist Farook Jahoor of the Chil-
dren's Nutrition Research Center
(CNRC) in Houston, Texas, led a team of
scientists in Houston and Jamaica in a
study of Jamaican children who had been
treated for malnutrition. Jahoor is an as-
sociate professor of pediatrics at Baylor
College of Medicine in Houston. The
center is a joint research facility of Bay-
lor and the U.S. Department of Agricul-
ture. The Agricultural Research Service,
USDA's chief scientific agency, is a key
partner in the CNRC.
The scientists found that some chil-
dren, even after recovering from their low
weight at birth, made less high-density
lipoprotein (HDL) apolipoprotein A-1.
This protein transports cholesterol to
the liver for removal from the body. It's
the key part of "good" cholesterol's abil-
ity to protect the heart. Many scientists
are studying its biochemical structure and
how it controls cholesterol.
Jahoor's study, published recently in
the December 1997 issue of the medical
journal Lancet, showed that the levels of
HDL apolipoprotein A-1 were related
directly to the birth weight of the chil-
dren: the lower the birth weight, the less
HDL apolipoprotein A-1 they made.
It's no secret that too much cholester-
ol is a factor in development of heart dis-
ease. For this reason, the population is
encouraged to eat a low-fat, low-choles-
terol diet. However, this study suggests
that those who were smaller than normal
at birth may need to be even more careful
and monitor their cholesterol levels more
Naturally, this study will have to be
confirmed by additional epidemiological
While other research in England sup-
ports Jahoor's hypothesis, further stud-
ies will need to be done-perhaps with
the Jamaican children-to confirm that
the protein is reduced throughout life and
affects cardiac health.
Jahoor's publication received exten-
sive media coverage, but will the link
prove itself as these children age?
And what does this finding mean for
children in other parts of the world, in-
cluding the United States?
It depends, explains Jahoor.
If low birth weight is a result of pre-
mature delivery, it may not be signifi-
cant, since these infants may simply not
have had enough time in the womb to
reach normal birth weight.
However, if low birth weight (less than
3 kilograms, or 6.6 pounds at term) is a
result of other factors, such as poor ma-
ternal nutrition or other causes of poor
fetal nutrition, the infant might have a
greater risk of developing heart disease
and/or diabetes later in life.
Jahoor and his colleagues are current-
ly studying these possibilities. If their
findings are confirmed, it might be im-
portant to inform parents of low-birth-
weight infants that their children may
have a greater risk of developing heart
disease or diabetes later in life. The par-
ents might then want to be particularly
careful about the cholesterol and fat con-
tent of their children's diets.
Parents may wish to make their chil-
dren aware of the greater risk, so they can
make appropriate diet choices to reduce
the risk as they age.
"Getting used to a diet is easier as a
child than changing eating habits later in
life," explains Jahoor. He cautions, how-
ever, that the study's findings are too pre-
liminary to make firm recommendations.
-By Jill Lee, ARS.
Farook Jahoor is with the USDA-ARS
Children's Nutrition Research Center at
Baylor College of Medicine, 1100 Bates
St., Houston, TX 77030;phone (713) 798-
7084, fax (713) 798-7119, e-mail
Agricultural Research/January 1999
F ace it. Fried chicken is finger-lick-
in' good because of the oil and
batter it's cooked in.
But that taste-tempting combi-
nation comes at a price: added fat
in our diets. Not surprisingly, the pres-
sure is on the fast food industry to curb its
products' fat content.
One solution is now cooking in New
Orleans, surprisingly, where the cuisine
is as hot, rich, and lively as the city itself.
There, scientists-turned-chefs have con-
cocted a new rice flour batter that absorbs
60 percent less oil than standard com-
mercial batters made from wheat.
A&B Ingredients, a Fairfield, New Jer-
sey, company, is exploring the rice bat-
ter's commercial potential under a
cooperative agreement with the develop-
ers-Frederick F. Shih and Kim W.
Daigle. They're both chemists at ARS'
Southern Regional Research Cen- SCO
ter in New Orleans.
"Our productuses flourfrom reg-
ular long-grain rice as the main in-
gredient," says Shih, who is in the
center's Food Processing and Sen-
sory Quality Research Unit. "But
we're also looking at other types of
rice," like short- and medium-grain
Currently, wheat flour holds
sway as the chief ingredient in com-
mercial batter products. Plunged
into the deep fat fryer, wheat gives
fried chicken, fish, and other foods
a crispy, golden coat and mouth-
But it can also make food greasy,
thanks in great part to the gluten it
contains. This key wheat protein
component not only keeps batter
fluffy and firmly attached to food, it
also binds tightly with oil molecules,
boosting the food's fat content, explains
For example, 3 ounces of batter-fried
chicken breast (meat only) contains 160
calories and 4 grams of fat, according to
ARS' Nutrient Data Laboratory in River-
dale, Maryland. With skin and breading
included, that number jumps to 220 cal-
ories and 11 grams of fat.
But Shih and Daigle's studies found
that the proteins and starch in rice flour
are chemically different from those in
wheat, retaining a weaker grip on oil.
Another plus: "It's less allergenic than
other grain flours," says Shih.
In experiments, they fried up various
rice batter formulations coated onto skin-
less chicken breast nuggets. They then
gently peeled off the coating and subject-
ed it to a solvent extraction procedure
that whisks away the oil for weighing and
"One thing you have to look for in a
batter is whether it forms a slurry well,"
says Shih. "It also has to be adhesive
enough to stick to the chicken, but it can't
be overly thick."
Though the normal rice batter cooked
well and absorbed substantially less oil
than wheat-basedbatters, it initially didn't
puff up as well. Nor did it always stay
coated on the meat.
Shih and Daigle overcame the prob-
lems by modifying the rice flour with
enzymatic and other treatments. This
produced a better batter with cooking
properties similar to wheat's.
The scientists have since applied for
patent protection and are helping A&B
Ingredients further evaluate the rice bat-
ter's oil-uptake properties.
"If we can show definitively that
there's a decrease in the fat content,"
says Robert Bost, company presi-
dent, "we'll take that information to
key fast-food interests."
Bost envisions abroad market for
meats like chicken, fish, and shrimp,
as well as vegetables like fried okra
and onion rings.
But ultimately, the true measure
of the batter's success lies in the taste
buds of consumers. By Jan Susz-
Frederick F. Shih and Kim W.
Daigle are atthe USDA-ARS South-
ern RegionalResearch Center, 1100
RobertE. Lee Blvd., P.O. Box 19687,
New Orleans, LA 70179; phone
Biochemist Kim Daigle and chemist Fred Shih
demonstrate fried chicken coating made from low-fat-
uptake rice flour batter.
Agricultural Research/January 1999
Better Diets for Delta Residents
combines science with public
outreach could help poor fam-
ilies in the lower Mississippi
Deltaregion live healthier lives.
Called the Delta Nutrition Intervention
Research Initiative (Delta NIRI), it brings
public outreach to the Agricultural Re-
search Service's longstanding nutrition
Like scientists at ARS' six nutrition
research centers, Delta NIRI researchers
will do laboratory work-often using
human volunteers-and will publishtheir
work in scientific journals. But their pa-
pers may also focus on innovative pro-
grams to help Delta families overcome
poor nutrition and other problems asso-
ciated with poverty.
Why this special initiative for the
Because families in that region often
experience low-birth-weight newborns
and high infant mortality. Mothers lack
prenatal care, which also contributes to
the problem. Cardiovascular disease and
diabetes cases are above national aver-
ages. And though the poverty rate for the
United States is at 13 percent, in the Delta,
it's 27 percent.
The Delta areas of Mississippi, Loui-
siana, and Arkansas are home to more
than 5.3 million people. They're areas of
low crime, with Catholic, Baptist, and
Methodist churches serving as key sour-
ces of services and information. About
34 percent of the population is African
American, with those citizens shoulder-
ing the biggest burden of the area's pov-
Delta NIRI, which started officially in
1995, has an FY 1999 budget of $3.1
million. Its members include research and
educational partners throughout Missis-
sippi, Louisiana, and Arkansas, includ-
ing three historically black 1890
land-grant universities. Many members
say the Delta NIRI project benefits from
the diversity of members-and institu-
At Pine Bluff, Arkansas, Edith Neal (right), chair of the University of Arkansas' Department
of Human Sciences, discusses with Delta resident Vanessa Woods the nutritional importance
of small garden plots for home vegetable production.
In addition to ARS, they are the Ar-
kansas Children's Hospital Research In-
stitute in Little Rock; Pennington
Biomedical Research Center in Baton
Rouge, Louisiana; University of Arkan-
sas at Pine Bluff; and Southern Universi-
ty and A&M College in Baton Rouge. It
also includes Alcorn State University in
Lorman, Mississippi, and the University
of Southern Mississippi at Hattiesburg.
Setting Correctives in Motion
Delta NIRI works like this. Say, for
example, a food scientist finds low iron
levels in students attending aDelta school.
After publishing these findings, the sci-
entist might want to work with a nutri-
tionist to create an iron-rich school snack
program. It would then be the communi-
ty's job to keep it running.
"We have 36 counties or parishes in
Louisiana, Mississippi, and Arkansas we
are studying. We don't tell people what
they need; we listen," says program ex-
ecutive director Margaret L. Bogle. "It's
a delta of cooperation-the schools, ARS,
and the communities.
"At the University of Arkansas at Pine
Bluff, we have five professionals in-
volved to support the initiative: a nutri-
tionist, a pediatric nutritionist, two food
scientists, and a home economist," says
Edith Neal, chair of the Department of
Neal says her group's main focus is to
improve people's lives in the Delta
through nutrition. She says she appreci-
ates the research facilities available to
"Pennington Biomedical has an in-
credible research facility, and Arkansas
Children's Hospital has access to the
medical community," says Neal. "In re-
turn, the four educational institutions in-
volved bring experience in teaching
research and outreach to address the spe-
cial needs of the Delta."
Neal says her group will look at diabe-
tes, cardiovascular health in adults, and
iron and folate in children-all of which
are linked to poor diets.
Agricultural Research/January 1999
Last year, Delta NIRI began by asking
500 Delta community leaders what they
saw as the key health and nutrition prob-
lems in the area. Ninety-seven percent
said the top nutrition problem is that res-
idents eat too many high-fat foods. Teen
pregnancy in Arkansas and high blood
pressure in Louisiana and Mississippi
were considered the top health problems.
They also said residents lacked nutri-
tion information or interest in eating a
healthy diet. Three-fourths of the leaders
said high food prices keep some from
eating healthy foods. Sixty-seven percent
said too few fruits and vegetables were
available. About 80 percent of the com-
munity leaders also worried that preg-
nant women were not eating right.
Surveying the Situation
"The survey is very important because
having the support of community leaders
means buy-in from the community," says
Neal. "And we find what they tell us re-
flects what we're seeing in epidemiolog-
ical literature-especially the input from
physicians, nurses, and counselors at the
WIC program." WIC is USDA's Special
Supplemental Food Program for Wom-
en, Infants, and Children.
Delta NIRI is now completing a sur-
vey of residents to gain more informa-
tion. "I'm encouraged by the leaders'
comments, because Delta NIRI can play
a role in nutrition education," Bogle says.
She also says the community survey may
show a better nutrition awareness than
Community members have been in-
volved in Delta NIRI's work from the
start. The program trained Delta residents
to do the surveys-which proved an in-
valuable asset for research accuracy.
Cooking practices in these rural South-
ern communities can influence diet and
health, which is one reason to have Delta
residents participate in the survey.
For example, many Delta families
make ends meet by eating wild-growing
poke greens. These have about the same
nutrient content as spinach or collard
greens, but how people cook their greens
"When a trained Delta NIRI research-
er hears somebody ate poke salad they
know to ask, "Okay, was that with eggs,
bacon, or plain?" says Bogle. "The per-
son's answer tells whether the food choice
added protein or fat. It's where knowing
cultural practices pays off."
But understanding Delta life does more
than enhance survey results. It can also
ensure that any programs developed are
Poverty in the Delta causes nutrition
barriers that are different from those
urban families face. Understanding these
problems makes it easier to find work-
able solutions. Take, for example, the
problem of providing children fresh fruit
Many poor families live on land unfit
for gardening and are generations re-
moved from farming know-how.
In the United States, 88.5 percent of
the driving-age population own a car, but
only 68 percent own one in the Delta.
Add a lack of refrigeration to unreliable
transportation, and produce isn't an op-
tion because of spoilage. Some Delta
grocers don't even stock fresh fruits and
Most people assume that people in the
Delta are farmers. The reality is that small
family farms are disappearing. And while
most farms are still family owned, they
are larger and fewer people are involved.
"Creating small garden plots for fam-
ilies is one possible solution," says Bo-
gle. "But is this something the community
will want-is it the most pressing need?
These are the kinds of things Delta NIRI
can help us find out."-By Jill Lee, ARS.
Margaret L. Bogle is with the USDA-
ARS Delta NIRI, 10825 Financial Centre
Pkwy., Ste. 309, Little Rock, AR 72203;
phone (501) 954-9152, fax (501) 954-
9596, e-mail firstname.lastname@example.org
At a farm in Gfady, Arkansas, nutritionist Margaret Bogle, director of the Delta Nutrition
Intervention Research Initiative, talks about the importance of eating fresh vegetables with
students from the Child Development Center at the University of Arkansas at Pine Bluff.
Agricultural Research/January 1999
"'"""""" ,,~.,,, o
Summer Program REAPS Lasting Benefits
One conversation with 17-year-
old Abra Parkman and you
know you're talking to a confi-
dent young woman ready to
embrace her future. This high
school senior has already accomplished
much, including attending an innovative
science program at Kentucky State Uni-
versity (KSU) developed in partnership
with USDA's Agricultural Research
Service and Natural Resources Conser-
For 2 years, Parkman, of Evansville,
Indiana, has spent half of her summer at
KSU's Research Extension and Appren-
ticeship Program, known as REAP. She
learned about this program when USDA
Liaison/Director Jesse K. Moore came
from Frankfort, Kentucky, to tell parish-
ioners at the Nazarene Mission Baptist
Church in Evansville about agriculture
and a chance to be part of the REAP ex-
The program gives students-eighth
graders to high schooljuniors-a chance
to live on KSU's Frankfort campus and
work with scientists and other agricul-
tural professionals every day for 6 weeks.
Their work includes publishing mini-
papers and giving oral presentations to
their peers, mentors, and others.
Parkman plans to attend college after
graduating from Benjamin Bosse High
School in Evansville. She's considering
becoming a zoo veterinarian-specializ-
ing in animal reproduction. She says
working with USDA's Animal and Plant
Health Inspection Service (APHIS) got
her involved in research right from the
"I got to see a veterinarian worming
cattle and taking blood to test for diseas-
es," she says. "It was really interesting to
see what was done with the animals."
Parkman's mentors, APHIS veterinar-
ians who do farmsite testing for cattle
diseases such as brucellosis, were so
impressed with her that they asked her
back for a second year. Because only
about 30 of roughly 150 REAP applicants
are accepted annually, repeat internships
are a special honor.
"Working with 1,000-pound animals
can be dangerous-they're not house
pets," says APHIS veterinarian Barry
Meade. "But Abra handles them quite
well. She's also learned two of the labo-
ratory tests we run. We rely on her a lot."
Parkman usually accompanies veteri-
narian John Hollis on his rounds and has
helped APHIS conduct a nationwide sur-
vey of horse owners and breeders about
special equine diseases that APHIS is
working to control. Her first REAP paper
was on brucellosis eradication efforts, and
this year she wrote about APHIS' mis-
sion and program scope.
Going Back a Decade
ARS began a special cooperative pro-
gram in 1988 with historically black 1890
schools to get minority high school stu-
dents excited about science careers.
The Kentucky State program started
in 1990, when KSU Dean of Agriculture
Harold R. Benson drafted the original
proposal and applied to USDA to become
a REAP school.
It costs $155,000 to offer the program
to about 30 students. Currently, USDA
contributes $50,000-half from ARS and
half from NRCS. KSU, Kentucky state
government, and various businesses con-
The students make several education-
al trips, including a visit to Washington,
D.C., to see the Capitol. They also make
a trip to Beltsville, Maryland, to tour ARS'
Beltsville Agricultural Research Center.
Students in Kentucky State University's Research Extension and Apprenticeship Program
visit the ARS National Visitor Center at Beltsville, Maryland.
The Maryland trip begins at the ARS
National Visitor Center, housed in a his-
toric log lodge that the Civilian Conser-
vation Corps built in 1936.
This year, one of the tour's hits was
botanist Eric Erbe's demonstration elec-
tron microscope. He uses liquid nitrogen
to freeze samples of living plant tissue in
research to help ARS find new controls
for nematodes-microscopic worms that
cost millions in crop damage each year.
One student asked how much he could
magnify a sample.
"About 250,000 times," Erbe replied.
"But the key thing is how you use the
system. It's just like your car: Just be-
cause it can go 100 miles an hour doesn't
mean you normally drive it that fast."
Marcus Thomas, a 15-year-old soph-
omore, wanted to know how Erbe began
his career. Erbe said he had been interest-
ed in microscopes since he was 6.
"I wanted to get an understanding of
how hegot into that career," said Thomas
after the demonstration. When asked if
he'd like to do similar work, Thomas
smiled shyly and said, "Maybe."
"Aren't you nervous about getting that
liquid nitrogen on your skin?" asked 16-
year-old Michael Carty of Charlotte
Amalie High School in St. Thomas, Vir-
gin Islands. Being so cold, liquid nitro-
gen can instantly freeze the skin.
"I've poured about a swimming pool's
worth of the stuff during my career," Erbe
replied. "After a while, it becomes sec-
ond nature. Liquid nitrogen could cause
injury, but we follow strict safety guide-
Erbe helped DeLaina Givens, a 15-
year-old junior, freeze a wildflower she'd
picked on the campus. A junior at Scott
County High School in Georgetown,
Kentucky, Givens has been learning a lot
through the REAP program, which she
heard about from a woman in her church
whose daughters had participated.
During a tour of the Beltsville dairy
facility, Givens held odorless, compost-
ed manure that had been turned into fer-
tilizer-one of ARS' many sustainable
agriculture projects. This kind of research
will reduce nitrogen runoff, a form of
"REAP really changed my whole out-
look on agriculture," Givens says. "I knew
I wanted to be a scientist, but REAP
showed me agriculture is more than
farms-it's also about protecting wild-
life and ensuring that what we eat is safe."
During her first year in REAP, Givens
did lab work for her mentor, engineer/
chemist Matt Byers with KSU's Com-
munity Research Service. Byers was
working on how plant pesticide exposure
affected farmworker health. This year,
Givens gave educational tours at the Sala-
to Wildlife Education Center on Ken-
tucky's native plants.
Not every REAP student becomes a
scientist. B. J. Carter, a 16-year-old sen-
ior at Paul Laurence Dunbar High School
in Lexington, Kentucky, plans a career in
law enforcement. But the REAP program
has enriched his life, he says, because
mentor Sherri Evans has given him a love
of horticulture and gardening.
"I had biology in school last year, and
REAP really helped me get more out of
it," he says. "I like science more since I
went through the program."
Whether it's building a lifetime love
of science or helping someone choose a
career, ARS scientists see that programs
such as REAP are vital to the survival of
their own research.
"This is really important for us," says
dairy scientist Albert Guidry, who is in
Beltsville's Milk Secretion and Mastitis
Research Unit, as the students toured the
dairy. "We communicate with our peers
through scientificjournals. But if we don't
reach the next generation and get them
excited about the work, who's going to
carry it on in the future?"-By Jill Lee,
Jesse K. Moore is the USDA Agricul-
tural Liaison, Kentucky State University,
Atwood Research Bldg., Frankfort, KY
40601; phone (502) 227-6738, fax (502)
Agricultural Research/January 1999 Agricultural Research/January 1999
In the Bag" !!
.,- .__ed a.- ljd- lji., t .e t tI e most popular items in the fresh produce
section of supermarkets today. The major reason: Salads are healthy
foods. They help consumers meet the recommended quota of five
servings each day of fruits and vegetables to maintain good health.
Sales of packaged lettuce in the United States were over $1.2 billion
From a food safety perspective, salads are considered by some to be among
the safest foods.
However, some segments of our population often exclude salads and other
uncooked fruits and vegetables from their diets. Because of the high levels of
microbial agents found on fresh-cut produce, salads are often not recommend-
ed for the young, old, pregnant, or immunocompromised. These people can't
risk exposure to microorganisms that, for the general population, are normally
For even though commercial food processors use chlorine to control mi-
Scrobes on fresh-cut lettuce, the treatment doesn't eliminate all the organisms
that can be present, such as Shigella and E. coli 0157:H7. Although E. coli is
primarily found on meat, it has recently shown up in apple juice, sprouts, and
4. lettuce. Outbreaks of food poisoning from ?slg II! on iceberg lettuce have
occurred in Sweden, England, and Wales.
Robert D. Hagenmaier, an ARS chemist at the U.S. Citrus and Subtropical
Products Laboratory in Winter Haven, Florida, has found a way to reduce these
Sand other pathogenic and nonpathogenic microorganisms. He combines an
S ionizing irradiation treatment with the chlorine wash. Technician Kelly Alger
assists with the research.
Ionizing radiation passes through food in the form of radiant energy, with-
out leaving any residue. It does not make food radioactive. Although the U.S.
Food and Drug Administration has approved up to I kilogray (kGy) of ionizing
irradiation for fresh produce, Hagenmaier uses much less.
In lab experiments, he found that irradiation significantly reduced the mi-
S crobial and yeast populations on cut iceberg lettuce. Eight days after zapping
Schlorine-washed lettuce with only 0.2 kGy of irradiation, microbial counts
i were 290 colony-forming units (CFU) and yeast, 60 CFU. Control samples that
had not been irradiated showed microbial counts of 220,000 CFU and yeast,
"Low levels of irradiation were used to minimize changes in the texture or
appearance of the lettuce," Hagenmaier says.
Irradiated lettuce had about the same shelf life as untreated samples. Nor-
mal shelf life claimed by manufacturers for retail sales of salads is between 14
and 16 days from the packaging date.
Hagenmaier also irradiated chlorine-washed, shredded carrots in modified-
atmosphere packaging. Nine days after irradiation, on the expiration date, the
microbial count was 1,300 compared to 87,000 for nonirradiated, chlorinated
controls, he says, and texture and appearance were unchanged.
"This research could help fresh-cut salads to be included in diets of people
Swho otherwise couldn't enjoy them because of a potential microbiological
health risk," Hagenmaier says.-By Doris Stanley, ARS.
Robert D. Hagenmaier is at the USDA-ARS U.S. Citrus and Subtropical
Products Research Laboratory, P.O. Box 1909, Winter Haven, FL 33883;
phone (941) 293-4133, ext. 123, fax (941) 299-8678, e-mail bobhagmr
Agricultural Research/January 1999
KEITH WELLER (K8313-1)
Software To Improve Food Safety
E ating chicken wings should be
a fun snack, not a deadly game
of chance. That's why food
technologist Thomas P. Oscar
and his colleagues in ARS' Mi-
crobial Food Safety Research Unit at
Princess Anne, Maryland, are constant-
ly improving their risk assessment soft-
ware-so poultry producers can make
the right decisions about food safety.
Computer software that can help with
tracking foodborne pathogens is becom-
ing more important to meat producers in
the wake of USDA's Hazard Analysis
and Critical Control Points prograin. The
HACCP regulation, which took effect
in 1996, requires all poultry procc,,.r,
to identify potential contamination iires
and take steps to reduce risk.
Last year, Oscar came out ilrh
S-RAMPP (Salmonella Risk
Assessment Modeling Pro-
gram for Poultry), a pro-
gram that models each
stage of poultry production .
by considering three micro- '-
reduction-effectiveness oi con
growth-speed at which micro-
organisms take hold and grn \.
Based on this information, it predicts
the numbers of Salmonella organisms
on poultry at each stage of production
and helps poultry producers decide
where they can apply efforts to improve
When S-RAMPP came out, it caught
the attention of several major poultry
producers. These companies have been
using the program to pre-test such
HACCP strategies as where to put an
extra washer, whether to increase
chlorine levels, or which changes will
be most economical and effective.
S-RAMPP is based on current scien-
tific knowledge and hundreds of exper-
iments done by Oscar's research team to
find how quickly Salmonella grow on
poultry, based on time, temperature, and
A release of the program,in Decem-
ber 1998, includes Campylobacter, an-
other important human pathogen found
on poultry. It is called Poultry FARM-
UP (Poultry Food Assess Risk Model for
Human Pathogens). It is easier to use than
But Oscar isn't stopping there. He's
going back to the lab to change how his
research team gathers data so future pro-
grams will be even more reliable. One
way he's doing that is by changing how
the lab grows Salmonella samples.
"Instead of using a laboratory medi-
um, we're going to be growing samples
on chicken parts such as breast and thigh
meat," he says. "Using real meat cuts will
allow us to study how competing micro-
organisms affect Salmonella growth."
To differentiate the Salmonella from
other bacteria, Oscar plans to use Salmo-
nella tagged withjellyfish genes to make
them glow. He obtained these special
Salmonella from microbiologist Pina
Fratamico at ARS' Eastern Regional
Research Center in Philadelphia, Penn-
Oscar says he also plans cooperative
projects with industry to see how ingre-
dients in commercial chicken franks or
patties slow or accelerate bacterial
growth. Salmonella is one of the most
commonly reported foodborne illnesses
in the United States, with reported infec-
tions doubling every two decades.
()Osar is also considering ways to use
these industry-focused data to help con-
u mers. One of his ideas is a computer
.ame named "Banquet" that could,
in a fun, humorous way, teach
consumers the serious lessons
of food safety.
By combining his data
with data from other agen-
cies on how much of a patho-
gen is needed for people to get
sick, Oscar envisions a game where
the chef's decisions could create either
an enjoyable meal or a culinary disaster.
The banquet's guest list would include
diners particularly vulnerable to Salmo-
,it IIa and Campylobacter, such as the
elderly and people with compromised im-
"So much of food safety is about con-
sumer education," says Oscar. "All the
efforts made at the processing plant or
the grocery store to keep meat safe are in
vain if the person preparing the food
doesn't use the same kind of care in pre-
venting foodborne illness."-By Jill Lee,
Thomas P. Oscar is in the USDA-ARS
Microbial Food Safety Research Unit,
1124 Trigg Hall, University ofMaryland
Eastern Shore, Princess Anne, MD
21853; phone (410) 651-6062, fax (410)
651-6568, e-mail toscar@umes-
Agricultural Research/January 1999
Barberpole Worms-Parasites of
T he barberpole worm is among
the world's most loathsome and
widespread stomach parasites of
sheep, goats, and cattle. They
feed on host animals' blood with
a voracious appetite.
Forfarmers, the headache begins when
approved drugs fail to protect their ani-
mals from this parasitic nematode that is
better known by its scientific name, Hae-
monchus contortus. There seems to be
evidence that the pest is showing signs of
resisting the effects of such pharmaceu-
tical controls. But new research under way
in Beltsville, Maryland, could undermine
the parasite's costly mischief by means
of biochemical sabotage.
Agricultural Research Service zoolo-
gist Raymond H. Fetterer is leading the
effort, along with chemist Marcia L.
Rhoads, parasitologist Dolores E. Hill,
and technician Ruth Barfield. Their chief
focus is to identify and exploit natural
substances that the barberpole worm se-
cretes while using its host as both room
By taking this route, they hope to set
the stage for developing new drugs or,
preferably, natural control agents "rela-
tively specific to the nematode and non-
toxic to the host," says Fetterer, who is at
ARS' Parasite Biology and Epidemiolo-
gy Laboratory in Beltsville.
The team's work comes at a time of
growing concern over evidence that many
nematode parasites may be developing
"In many parts of the world, including
the United States, drug resistance is be-
coming a problem, particularly with
Haemonchus in sheep," says Fetterer.
Going for the Gut
Scrutinizing the barberpole worm's
biochemistry could yield much-needed
alternatives, including new substances for
creating animal vaccines. "We have along
way to go before that point," cautions
Fetterer, "but we have some good candi-
These include a potent cocktail of di-
gestive proteins and enzymes the scien-
tists recently discovered after cutting into
the parasite's long, thin intestine. Their
focus now: confirm a suspicion that the
cocktail helps the barberpole worm di-
gest its host's red blood cells. They're
also trying to purify the cocktail's active
ingredients so the size, molecular struc-
ture, and function can be described.
Fetterer refers to a key group of pro-
teins as hemolytic factors (HFs). He be-
lieves the proteins are localized within
membranes of the parasite's gut. There,
like "molecular drill bits," they punch
Zoologist Kay Fetterer and technician Kuth
Barfield draw a sheep's blood sample for
analysis to see how the brown stomach
worm causes red blood cells to collapse and
lose hemoglobin. The goal is to develop an
antibody to this parasitic nematode's
holes into the walls of ingested blood
cells, causing hemoglobin to seep out.
Millions of years of evolution have
equipped the barberpole worm with a
single, toothlike structure for scraping its
host's stomach tissues to cause bleeding.
"It feeds by sucking up the blood, tis-
sues, and anything that happens along,"
By secreting the HF proteins, he pro-
poses, the parasite can then extract he-
moglobin and other important nutrients
from the blood cells.
Another player in the digestive pro-
cess is the cysteine protease enzyme. "It
helps break down the hemoglobin and
other ingested proteins into smaller frag-
ments," further aiding absorption, says
His lab is now conducting an informal
study with scientists who are with En-
zyme Systems Products in Livermore,
California, to see if substances called
inhibitors will obstruct cysteine protease
activity in the barberpole worm. If so, the
approach could deprive the parasite of a
key nutrient-gathering tool.
In addition to the barberpole worm,
"some insects also have these types of
enzymes," notes Fetterer. One such in-
sect is the stable fly, from which research-
ers took their cue in searching for the
barberpole worm's digestive cocktail. "If
youjust think about getting nutrients from
a cell," says Fetterer, "then what you end
up having to do is break it open."
The scientists began their search for
that cell-breaking factor by grinding a
barberpole worm's intestine and mixing
a small amount of extract material with
red blood cells from sheep. Normally,
sheep red blood cells appear as smooth-
surfaced disks with a slight dimple, or
indentation, in the center. But exposing
the cells to the parasite's hemolytic pro-
teins quickly distorted their shape.
Images captured with a scanning elec-
tron microscope's high-powered eye re-
vealed that the surface of the cells began
to buckle after 15 minutes. By 30 min-
utes, jagged projections emerged, mak-
ing the cellular surface appear harsh and
alien. The cells also began losing hemo-
globin, which escaped through holes that
Agricultural Research/January 1999
had opened up. By 90 minutes, the cells
began to break apart, deflating as the last
of the hemoglobin escaped.
"These observations support a hypoth-
esis that the hemolytic factors serve as
pore-forming agents," says Fetterer.
"They insert themselves into red blood
cell membranes, altering their structure
and thus causing them to rupture.
"One of our goals," Fetterer contin-
ues, "is to further purify and characterize
this hemolytic factor and see if we can
develop an antibody to it."
An antibody also raises the prospect
for developing a vaccine. Injected into a
lamb, for example, a vaccine could help
prime the young animal's immune sys-
tem for nematode attack.
"There are no such vaccines currently
available for controlling these parasites,"
Until then, anthelmintics-drugs that
destroy or expel parasitic worms-will
remain the staple defense. While effec-
tive, such chemotherapy isn't a magic bul-
let. That's because even a treated animal
can reacquire the parasite by grazing on
infected pasture, necessitating yet anoth-
er round of treatment. To avoid this cost-
ly cycle, farmers must be diligent about
where and when they put their animals
out to graze.
Sheep are especially vulnerable to
barberpole worm assaults. For one, sheep
aren't averse to grazing pasture where
manure is present that may contain para-
site eggs, according to Virginia Cooper-
ative Extension scientists in Blacksburg.
Sheep also graze plants close to their
roots, where parasite larvae are most con-
centrated. To make matters worse, "the
larvae are actually specialized at crawl-
ing up grass blades where they can be
ingested," adds Fetterer.
Once ingested, parasite larvae quick-
ly find their way into the host's aboma-
sum, or true stomach. There, they mature,
mate, and produce eggs in about 21 days.
A scanning electron micrograph of a
sheep's blood sample shows healthy red
cells. Magnified about 6,000x.
CHARI FR MUlRPHY
.| .. .
Red cells in blood of a sheep exposed to
hemolytic proteins from barberpole worms
are rough and misshapen. Magnified about
In susceptible or young animals, par-
asite numbers can build so high that the
animal loses more blood than its body
can replace. Severe blood loss can kill an
animal, says Fetterer. Milder or chronic
infections can cause lethargy and loss of
appetite and can interfere with weight
gain. This affects a producer's profit when
animals show a drop in their milk, meat,
or-in the case of sheep-wool produc-
Setting the Stage for Parasite
Fetterer's hope is that what is learned
about the barberpole worm's key weak-
nesses will also apply to some other nem-
atode parasites, like the brown stomach
worm, Ostertagia ostertagi. In the Unit-
ed States, this parasite-more than the
barberpole worm-is a menace to beef
cattle, especially heifers and breeding
"Ideally, we'd like to find something
common to the Trichostrongylidae," says
Fetterer. This nematode family includes
Haemonchus, Ostertagia, and about ahalf
dozen other species known to parasitize
Next to antibiotics, administering ant-
helmintic drugs is often a farmer's sec-
ond highest production cost, Fetterer says.
So, "if you could reduce the reliance on
chemotherapy, you could reduce costs."
That's especially important in light of the
barberpole worm's increasing drug re-
Additionally, organically grown pro-
duce, including milk and meat products,
is becoming more popular with Ameri-
can consumers-all of which opens the
door to novel methods for protecting live-
stock and farmers' profits.
"The long-term rationale for doing this
research is to understand how nematodes
survive and adapt to their hosts," says
Fetterer. "Such knowledge can lead to
the development of new tools for pro-
ducers to use so they can choose what's
best for their particular management
styles."-By Jan Suszkiw, ARS.
Raymond H. Fetterer, Marcia L.
Roads, and Dolores E. Hill are at the
USDA-ARS Parasite Biology and Epide-
miology Laboratory, Rm. 103, Bldg.
1040, 10300 Baltimore Blvd., Beltsville,
MD 20705-2350; phone (301) 504-8300,
fax (301) 504-5306, e-mail rfetterer@
Agricultural Research/January 1999
Making Coccidia Less Cocky
ers raise about 7 billion broil-
ers. That's a lot of beaks to feed.
And feed is the costliest item
on the producer's balance
sheet-topping even labor costs.
That's why chickens are routinely
given drugs to prevent infection by tiny,
single-celled protozoa known as coccid-
ia. These organisms invade cells in a
chicken's gut, where they reproduce and
make it harder for the bird to absorb feed
and gain weight quickly.
Coccidiosis is among the top-five
chicken diseases that prevent weight gain,
says Agricultural Research Service mi-
crobiologistHarry D. Danforth. Heis with
ARS' Parasite Biology and Epidemiolo-
gy Laboratory at Beltsville, Maryland.
Each year, the protozoa cost producers
worldwide an estimated $600 million in
treatment and low carcass weights.
And it could become worse, because
the protozoa are developing resistance to
standard drugs. That has Hyun S. Lille-
hoj and Mark C. Jenkins, who are based
at the ARS Immunology and Disease
Resistance Laboratory at Beltsville,
working on ways to use the birds' own
immunity against coccidia. "We have
short- and long-term goals," says Dan-
forth, who is the agency's scientific liai-
son with the poultry industry. The
short-term goal is a gamma-irradiated
vaccine Danforth tested this year at Per-
due Farms, Inc., in Salisbury, Maryland.
First, however, Jenkins had to deter-
mine the radiation dose needed to weak-
en the live oocysts-the infectious stage
of coccidia. This prevents them from
developing or reproducing. Next, he fig-
ured the dose of weakened oocysts need-
ed to produce immunity in the chicks.
Then, Danforth put the oocysts in a gel
delivery system he and researchers in the
vaccine industry had developed earlier to
get live vaccine into chicks at the hatch-
ery. The gel was added to the feed of
chicks destined to become Cornish hens.
Danforth says ittakes about 1.6 pounds
of feed for each pound of bird. With the
gamma-irradiated oocysts, "feed conver-
sion was 3 points better than with the
anticoccidial drugs," he says. "That
means the treatment reduced, by three
hundredths of a pound, the feed needed
to raise a 2-pound Cornish hen. That may
seem small, but it's nothing to sneeze at
when multiplied by thousands or millions
of birds. The company would realize an
extra $1 million a year for its Cornish
hens alone, says Danforth.
Donna Hill, Perdue' s director of health
services, says the vaccine had other ben-
efits. The birds were more uniform in size
and had good color. The results were so
promising that "if it were commercially
available, we would probably start using
an attenuated vaccine right away for
Cornish hens and begin testing it on broil-
ers," she says.
Trouble is, it takes 10,000 of the killed
oocysts to immunize each bird, and the
oocysts have to be grown in live chick-
ens. About 40 billion gamma-irradiated
oocysts per week would be neededjust to
inoculate all the broilers raised by Per-
due alone, says Danforth. "It's a num-
bers game. We're trying to give the
producer some relief now, until research-
ers streamline ways to enhance chickens'
immune response to coccidia."
And that's no easy task.
Agricultural Research/January 1999
Not Too Little-Not Too Much
The chicken's immune system is more
complicated than a Chinese puzzle. And
launching an immune response is walk-
ing a fine line. It can protect a bird-or
destroy it, if it goes too far. So research-
ers first have to unravel the complex inner
workings in the bird's gut before they
can get the optimum immune response
without an overreaction.
Jenkins approached this problem by
identifying proteins in the oocysts that
mark it as an intruder and elicit an im-
mune response. He, Lillehoj, Danforth,
and Michael D. Ruff have a patent on the
recombinant DNA for two
promising proteins from the
oocysts' outside coat.
Jenkins inserted the re-
combinant DNA for those
two coat proteins and anoth-
er promising protein sepa-
rately into DNA loops, called
plasmids, taken from E. coli
bacteria. In small-scale tests at the Belts-
ville lab, he shot the plasmids straight
into chicken legs using ajet gun, like the
ones dentists use to numb their patients'
teeth and gums.
"We got the best protection with mix-
tures of all three plasmids," Jenkins says.
Weight gain in the immunized chicks
was significantly better than in the un-
immunized birds. But it was not as good
as in the birds that never got close to a
coccidia oocyst. "We have a little way to
go because we want to have complete
protection," he says. And a more effi-
cient system for delivering such an inoc-
ulum in an industry setting is needed.
Lillehoj' s lab identified another prom-
ising protein. It enables the stage that
emerges from the oocyst, called a sporo-
zoite, to invade the bird's T cells. Lille-
hoj patented a monoclonal antibody to
the protein that she says "consistently
blocks this invasion in culture dishes."
She is now collaborating with scientists
in Japan and Korea to find the DNA that
directs production of that protein.
The All-Natural Boost
Lillehoj's main focus is on the sub-
stances immune cells generate to com-
municate with one another. Animals
produce these natural, hormonelike chem-
icals, called cytokines, during an infec-
tion. They are potent and function at low
Some cytokines enhance the immune
response. But others can cause disease
symptoms, "so you have to know which
ones are protective," says Lillehoj. "Un-
derstanding how this works may be a way
to control infection without introducing
The chicken' imuntt tit'iem i'
more complicated than a Chintm
She is looking for umbrella protection
against the six or seven chicken coccidia
species because, once cytokines are pro-
duced, they aren't picky about the spe-
cies. They may also be given along with
vaccines to increase their effectiveness.
The challenge is that there are more than
20 different cytokines that regulate im-
mune response, Lillehoj says. "We'rejust
beginning to understand how they work."
One all-purpose cytokine that has
proved effective is interferon gamma. (See
"Two Strategies for Protecting Poultry
From Coccidia," Agricultural Research,
Oct. 1996, pp. 12-13.) Interferon gamma
activates macrophages-cells that behave
like the Pac Men of the immune system,
gobbling up invaders. Interferon gamma
inhibits coccidia multiplication, so the
birds lose less weight. Lillehoj says the
birds' immunity level correlates with their
interferon gamma level.
Another cytokine that's showing prom-
ise in laboratory tests is interleukin-15.
IL-15 prompts the all-important, infec-
tion-fighting T cells to multiply. Last year,
Lillehoj's lab cloned the gene for IL-15,
and they are testing its use under three
In one, they inject the IL-15 protein
the gene produces directly into the chick's
muscle. In another, they use a gene gun to
inject the chick with the naked IL-15
DNA. And in the third, they insert the
DNA into a vector, such as a weakened
version of the fowl pox virus that is now
used to immunize poultry against fowl
"All three methods enhance the chick-
ens' innate immune response against
coccidia," Lillehoj says. "The animals
have more T cells, which are critical for
defense, and they lose less
Lillehoj is collaborating
with three companies on chick-
en cytokine research. But
progress has been slow, she
says, because knowledge
about human cytokine DNA
isn't much help. Poultry DNA is only
about 30 percent similar to human DNA,
compared to a 70-percent similarity in
large meat animals.
Lillehoj is also collaborating with
Perdue on a different tactic for control-
ling coccidiosis. Since some chickens are
genetically more resistant to the disease
than others, her lab is searching for the
genes that confer this resistance. Once
they are identified, poultry producers can
breed for the hardiest birds.-By Judy
Harry D. Danforth is at the USDA-
ARS Parasite Biology and Epidemiology
Laboratory, 10300BaltimoreAve., Belts-
ville, MD 20705-2350; phone (301) 504-
8300, fax (301) 504-5306, e-mail
hdanfort@ lpsi. barc. usda. gov.
Mark C. Jenkins and Hyun S. Lillehoj
are at the USDA-ARS Immunology and
Disease Resistance Laboratory, 10300
Baltimore Ave., Beltsville, MD 20705-
2350; phone (301) 504-8201, fax (301)
mjenkins@ lpsi.barc. usda.gov
Agricultural Research/January 1999
cultural Research Service and
industry scientists, this powdery
byproduct of burning coal to
generate electricity is now help-
ing dairy farmers mud-proof their barn-
yard feedlots. That's where heavy winter
or spring rains quickly turn soils to knee-
deep mud, bogging down hefty cows, sub-
jecting them to disease, and sapping them
of energy to produce milk.
But research has shown that by paving
feedlot areas with a hydrated form of fly- Wet weather has turned this feedlot into deep mud.
Low-Cost Way To Pave Feedlots
"Flyash" could become the latest buzzword around the barnyard.
ash, farmers can build a solid foundation
to give their cows a leg up on mud. Not
only is flyash cheaper than paving with
concrete-$6 per square yard versus
$75-it poses little danger to the envi-
That's the verdict from pilot studies
conducted by ARS soil scientist William
L. Stout in cooperation with professional
geologist Thomas L. Nickeson of Wells-
boro, Pennsylvania, and two commercial
partners-Gerry Thompson of Air Prod-
ucts and Chemicals (AP&C), an Allen-
town, Pennsylvania, company; and Paul
Cunningham of Black Rivers Co-Gen
Partners, a Fort Drum, New York, power
One study, conducted in 1995-96 on
an experimental dairy farm north of
Harrisburg, Pennsylvania-and funded
by the U.S. Department of Energy-ex-
amined the environmental impact of
spreading 33 tons of flyash onto a 900-
square-foot feedlot. Researchers applied
a form of flyash gleaned from a coal-
burning process called fluidized-bed
combustion that is employed by the elec-
tric utility industry.
Using instruments called suction
lysimeters, the team monitored the con-
centrations of various elements andheavy
metals seeping into groundwater from the
flyash pads. Later, they compared the data
with that collected from an unpaved feed-
lot, says Stout, who is at ARS' Pasture
Systems and Watershed Management
Research Laboratory in University Park,
Though lab analysis revealed minute
traces of elements like calcium and nick-
el, a heavy metal, "we weren't able to
Cattle have a firm footing in this barnyard lot paved with ash produced at the Fort Drum
(New York) Cogeneration Facility.
Agricultural Research/January 1999
"Star Wars" Technology May Solve
Down-to-Earth Insect Problem
detect anything at unacceptable levels,"
says Stout, referring to threshold levels
for safe drinking water set by the U.S.
Environmental Protection Agency.
Based on results from the Harrisburg
study and other earlier ARS projects, the
New York Department of Environmen-
tal Conservation subsequently approved
farmer use of flyash as a safe barnyard
paving resource. Follow-up studies con-
ducted by Nickeson and collaborators at
AP&C and three other companies also
expedited approval in parts of El Nifio-
Mike Huggins, of the San Joaquin
County Environmental Heath Division,
said five dairy operations in his jurisdic-
tion have paved their lots with a local
plant's flyash to protect their cattle from
high water and muddy conditions that
"Right now, we have the University
of California-Davis Medical Veterinary
School looking at flyash from an animal
health standpoint," says Huggins. Evi-
dence collected from the farms thus far
points to a sharp drop in cases of hairy
footwort, a viral hoof infection, and mas-
titis, a bacterial udder disease.
For Nickeson, using flyash to pave
feedlots is a win-win situation for both
the electric utility industry and dairy pro-
ducers. By selling the flyash, power
plants save money on waste disposal;
by using it, farmers safeguard their cat-
tle's welfare and ensure peak milk pro-
duction and growth during the rainy
Paving also helps direct manure to-
wards waste utilization systems, says
Stout. That helps reduce the potential
for nitrogen and phosphorus to contam-
inate groundwater.-By Jan Suszkiw,
William L. Stout is at the USDA-ARS
Pasture Systems and Watershed Man-
agement Research Laboratory, Curtin
Rd., University Park, PA 16802-3702;
phone (814) 863-0947, fax (814) 863-
0935, e-mail email@example.com. *
Research is often like the rising tide that lifts all boats: One scientist's discoveries
sometimes help colleagues in a completely unrelated field. That's how ARS entomol-
ogist Guy J. Hallman found himself controlling insects with electrical pulses.
At ARS' Crop Quality and Fruit Insect Research Unit in Weslaco, Texas, Hallman
studies ways to prevent insect pests from hitchhiking on exported citrus. New methods
for certifying U.S. citrus as pest free are needed before a U.S. Environmental Protec-
tion Agency ban on the fumigant methyl bromide takes effect in 2005.
Methyl bromide is currently the workhorse of fumigants used on a variety of crops
in postharvest processing. But its days are numbered because it may deplete the Earth's
While scanning the scientific literature one day, a technical report by Q. Howard
Zhang grabbed Hallman's attention. Zhang, a food processing engineer at Ohio State
University, had used pulsed electric fields (PEF) to inactivate microbes such as Es-
cherichia coli in food. "I imagined PEF technology might also kill fruit fly eggs and
larvae in citrus," Hallman said.
PEF releases microsecond bursts of high-voltage electrical current. Unlike contin-
uous current, PEF generates only a tiny amount of heat. Applied to certain foods, the
process, called cold pasteurization, avoids changes in color, flavor, texture, and nutri-
ents that might occur with thermal pasteurization.
Zhang himself had earlier been given a boost by researchers in a completely un-
In a lucky find, the Ohio State researcher uncovered an electrical pulse generator
while exploring outmoded equipment shelved by the National Aeronautic and Space
Administration. Researchers working on the Strategic Defense ("Star Wars") Initia-
tive had used the generator to test communications microwave tubes.
After reading Zhang's report, Hallman suspected that, since insects are more com-
plex than bacteria, PEF could destroy citrus pests with less than the 25,000 volts
needed to kill E. coli. Hallman contacted Zhang, and the two began collaborating on
trials using PEF to control a dangerous citrus pest-the Mexican fruit fly.
The researchers exposed fly eggs to ten 50-microsecond pulses of about 9,000 volts.
Each pulse lasted for only 1- 20,000th of a second, but that was enough-less than 3
percent of the eggs hatched. Of the few that hatched and became larvae, none survived
Larvae proved even more vulnerable to PEF. None treated with as little as 2,000
volts lived past the pupal stage to adulthood. "Judging from the larvae's inability to
recover from general paralysis," Hallman says, "we think PEF is very damaging to
their nervous systems."
Is PEF an immediate candidate to replace methyl bromide? Hallman says it's not.
"A great deal more research is needed before we use PEF as a quarantine treatment."
To that end, ARS is seeking an industrial partner to explore the potential for treating
citrus with PEF.
Equipment limitations have thus far prevented the researchers from assessing PEF' s
effect on fruit quality. Future studies must also determine the economic feasibility and
efficacy of PEF before the procedure could be approved for citrus certification.
Still, Hallman says, "It's imperative we examine a host of novel approaches that
may come from work completely unrelated to insect control. No single method will
completely replace methyl bromide."-By Ben Hardin, ARS.
Guy J. Hallman is in the USDA-ARS Crop Quality and Fruit Insect Research Unit,
2301 S. International Blvd., Weslaco, TX 78596; phone (956) 565-2647, fax (956)
565-6652, e-mail firstname.lastname@example.org. *
Agricultural Research/January 1999
Winterfat Seeds Take Ice Stakes Through
harp ice crystals in the seed embryo mean instant death
for most seeds-but not for those of winterfat, a low-
growing shrub that thrives from the Yukon to Mexico.
ARS studies have shown that sopping wet winterfat
seeds from Wyoming, Colorado, and Saskatchewan,
Canada, can survive temperatures at least as low as -220F.
So how does this native seed of the spinach family do it?
And, can this ability be transferred to major crops?
Terry Booth, a rangeland scientist with USDA's Agricultur-
Magnified view of normal cells
and tissue of a germinating
winterfat seed at 32oF.
When frozen, germinating
winterfat seeds withstand
formation of large ice crystals
(seen as dark holes in this
magnified view) and continue
growth after thawing.
al Research Service in Cheyenne, Wyoming, is going to great
lengths to find out. Most recently, he visited ARS cytologist
William P. Wergin in Beltsville, Maryland, to look at the seeds
through a scanning electron microscope specially designed to
view frozen tissue.
Booth soaked and froze the seeds to simulate the West's
freeze-thaw cycles. Particularly in the spring, seeds often get
wet from snowmelt during the day and then, overnight, the
water in the seeds turns to ice crystals. Or the seeds get wet and
start sprouting during a warm spell, only to be frozen by win-
terlike spring storms.
Booth, working with Yuguang Bai, who is with Agriculture
and Agri-Food Canada in Kamloops, British Columbia, and
Jim Romo, with the University of Saskatchewan, found that
water absorption before germination is greatest for seeds soaked
at 40oF or lower. Most seeds have a greater risk of freezing
damage as their water content increases.
Winterfat, however, often grew better when it had been
soaked at cold temperatures before freezing. Seedling vigor
also varied by where the seeds were collected, indicating that
the plants have evolved so that the germination requirements of
the seeds fit local climate variations. "So it's generally best to
plant seed collected locally," Booth says.
Under magnification, Booth saw ice crystals in the embryos
of seeds that were frozen at -220F before being plunged into
and stored in liquid nitrogen to preserve any internal ice crys-
tals, as well as nearby tissue. What surprised him was that the
tissue was freeze-dried, with only occasional large ice crystals
and no indication of normal cellular structure.
"A key part of winterfat's tolerance to freezing seems to be
its ability to hydrate, dehydrate, and rehydrate again without
significant damage," Booth says.
That intrigues Booth because of his suspicion that winterfat
may fight ice with ice. The hairy layers that cover winterfat
seeds appear likely to promote ice crystal formation. If ice
crystals form first in the outer layers, these crystals may suck
water from the embryo, aiding a freeze-dehydration process
that limits damage caused by embryo ice. It may keep the larg-
est crystals out of the embryo.
"But we need to spend a lot of time analyzing photographs
taken through the microscope before we can reach any conclu-
sions," he says.
Booth finds the winterfat shrub's ice tolerance as interesting
as that of the Antarctic nematode that is the only animal known
to survive with ice in its cells.
But there is a very practical purpose to Booth's research.
Winterfat is important as a food source for cattle in the western
United States and as nesting cover for ducks on Canadian prai-
ries. Forthe latterreason, Ducks SCOTT BAUER (K8219-1)
Unlimited, Canada, funded part
of the research. The U.S. Bu-
reau of Land Management, the l
USDA Forest Service, and min-
ing companies plant winterfat
on degraded rangelands and
strip-mined areas.-By Don
D. Terrance Booth is at the
USDA-ARS High Plains Grass-
lands Research Station, 8408
Hildreth Rd., Cheyenne, WY
82009-8899; phone (307) 772-
2433, fax (307) 637-6124,
Seeds of the winterfat plant,
Eurotia lanata, can be har-
vested in October.
Agricultural Research/January 1999
DEP TAN FEMNATIN
For Cheaper Bioinsecticides
F factory and field technologies,
advancing together, may put a
friendly fungus in the forefront
of a new bioinsecticide service
Growers of high-value horticultural
and vegetable crops could be the first to
benefit from Agricultural Research Serv-
ice work with industry to mobilize the
fumosoroseus against KEITH WELLER (K8311-1)
silverleaf and green-
mass-culturing P. fu-
mosoroseus may later
be adapted to different
fungi suited to protect-
ing turf grasses from
insects. Companies that
provide care for lawns
and golf courses could .
then apply more envi-
pest controls. Such serv-
ices may have special
appeal to families with
young children or pets.
"The idea is to pro- Microbiologist IV
duce and dry fungi in a Paecilomyces fun
factory and parcel them dryer.
to portable fermentors
at field sites where they
can be rejuvenated,
multiplied, and applied
through spray or irriga-
tion systems," says Mark A. Jackson. He
is a microbiologist at ARS' National
Center for Agricultural Utilization Re-
search (NCAUR) in Peoria, Illinois.
The scientists use a portable fermen-
tor patented by Eco Soil Systems, Inc., of
San Diego, California, under a 3-year
cooperative research and development
agreement begun last summer. Eco Soil
technicians now use the fermentation sys-
tem, called BioJect, to produce fresh
batches of nitrogen-fixing bacteria for
application through irrigation sprinklers
to make golf course grass greener and
In the beginning stages of his research
on P. fumosoroseus, Jackson modified
deep-tank fermentation technology devel-
oped by NCAUR a half century ago. The
technology originally launched an arse-
nal of antibiotics against human disease,
beginning with penicillin. Since applying
for a patent about 3 years ago, Jackson
and his colleagues have steadily improved
lark Jackson checks dried spore preparations of the
osoroseus after removal from a small, commercial-
mass spore production of P. fumosoro-
seus, doubling the number of spores pro-
duced in a tank and cutting fermentation
time from 3 days to less than 2. Along the
way, they developed fermentation mix-
tures that are more economical than the
precisely defined recipes used earlier.
"Our main goal has been to produce
spores that will do theirjob dependably in
the greenhouse and in the field," says
For factory-produced fungi to become
commercially viable, even for use in port-
able fermentors, large and predictable
numbers of healthy spores must be pro-
duced months in advance. The spores
should survive freeze-drying and long-
term storage. In recent laboratory stud-
ies, the scientists found about 75 percent
of freeze-dried spores remained alive after
5 months of storage.
To further lower bioinsecticide costs,
scientists are defining conditions that
allow the fungus to
multiply rapidly in
After small packages
freeze-dried spores are
mixed with nutrients
in the fermentors, the
spores spring vigor-
ously from their Rip
Van Winkle state and
multiply 100- to
fresh, active spores
produced on site can
be sprayed directly on
the crop to infect and
As research with
fungus Eco Soil Systems
scale freeze- progresses, Jackson
plans to inoculate
BioJect fermentors at
several ARS locations
and commercial field
sites. His research on
control of whiteflies
with P. fumosoroseus also involves col-
laboration with other industrial and aca-
demic scientists in Mexico, Spain, and
the United States.-By Ben Hardin,
Mark A. Jackson is at the USDA-ARS
National Center for Agricultural Utili-
zation Research, 1815 N. University St.,
Peoria, IL 61604; phone (309) 681-6283,
fax (309) 681-6427, e-mail jacksoma @
mail.ncaur. usda.gov. *
Agricultural Research/January 1999
ture to decode nearly all
genetic material in a flov
plant called Arabid
thaliana-a member (
mustard family-is speeding ahf
schedule. And the project is already
tening the discovery of impor-
tant genes in crop plants.
A. thaliana, also known as
mouse-ear cress or thale cress,
has become a workhorse of plant
biotechnology because it has
only a small amount of genetic
material. A small genome helps
simplify the task of determining
the exact sequence, or order, of
the four chemical subunits that
make up genetic material or
DNA. Every plant gene is com-
posed of a unique sequence of at
least a thousand of these sub-
units, or bases.
Scientists sleuthing Arabi-
dopsis originally estimated that
they would finish their prece-
dent-setting task by 2004, says
molecular biologist Athanasios
Theologis. He directs theArabi-
dopsis sequencing project at the
ARS/University of California at
Berkeley Plant Gene Expression
Center in Albany, California.
Now, researchers expect to fin-
ish by 2000, giving the world
what has been described as "the
first essentially complete cata-
log of all the genes involved in
the life cycle of the typical plant,
from seed to flower to fruit."
Theologis and colleagues at Sta
University in Stanford, Californi;
the University of Pennsylvania in ]
delphia use an approach called
throughput DNA sequencing. It is a
the newest, cheapest, and fastest w
find out the sequence of base units i
long strands of tightly coiled DNA
chromosomes of Arabidopsis.
A Model Plant Genome
Once the sequence of bases is known,
it is promptly posted on GenBank, an up-
to-the-minute Internet compilation that
also displays mouse, human, and other
sequences. Scientists can use GenBank
to look for sequences other organisms
have in common. Because similarities in
KEITH WELLER (K3954-7)
Tissue-cultured Arabidopsis thaliana.
sequence often indicate similarities in
function, searching for sameness via com-
puter quickens the discovery of a gene's
Once biotechnologists discover the
sequence and function of a gene, they may
be able to move useful genes into plants
that lack them, such as a gene for disease
resistance, for example. Or they might be
able to rebuild a gene to boost its effec-
Theologis and co-researchers have
already discovered about 500 Arabidop-
sis genes. Currently, the team sequences
about one gene a day. High-throughput
DNA sequencing offers that payoff be-
cause it focuses on finding sequences first
and leaves the question of a gene's func-
tion for later.
In contrast, the conventional
Approach begins by investigating
a function or trait first, then finds
the gene responsible for the trait,
and finally decodes the gene's
sequence. That one-by-one ap-
proach, says Theologis, costs
ii. millions, while finding a gene
with high-throughput DNA se-
quencing averages only a mod-
est $2,000 per gene. Theologis
expects the price to drop even
The National Science Foun-
dation, U.S. Department of En-
ergy, and ARS are funding the
work at Albany. Foundation and
Energy Department funds are, in
addition, going to Stanford, Phil-
adelphia, and four other U.S.
labs. Scientists in Japan and Eu-
rope are also part of the quest to
unlock all of the sequences in the
Arabidopsis genome.-By Mar-
cia Wood, ARS.
Athanasios Theologis is at
the USDA-ARS/University of
California at Berkeley Plant
Gene Expression Center, 800
Buchanan St., Albany, CA 94710;
phone (510) 559-5911, fax (510)
559-5678, e-mailtheo@nature. berkeley.
Visit the Plant Gene Expression Cen-
ter's Genome Sequencing Laboratory
on the WWW at http://pgec-genome.pw.
Agricultural Research/January 1999
Amino Acid Supplement
May Help People With
Can people infected by HIV improve
their antioxidant status with supplements
of cysteine, an amino acid? Scientists in
Texas have findings that may help an-
swer this question. Antioxidants boost the
body's immune system. They also pro-
tect our organs from damage by a destruc-
tive form of oxygen normally produced
in cells' metabolic reactions. But medi-
cal researchers know that levels of the
antioxidant glutathione (GSH) can fall
as a result of HIV infection. HIV patients
with low GSH levels have increased sec-
ondary infections and cancers and higher
mortality. But some scientists have shown
that a form of cysteine called NAC, short
for N-acetylcysteine, can raise GSH.
Other studies suggest NAC is ineffective.
In the Texas study, HIV-infected volun-
teers who took NAC increased their GSH-
making efficiency. The amount of GSH
in blood cells increased. This confirms
other findings-in the United States,
Brazil, Mexico, and Germany-that NAC
is helpful. The Houston study may also
shed light on why HIV infection lowers
GSH. The scientists concluded that the
HIV-infected volunteers may have been
producing the antioxidant too slowly
rather than using it too quickly. The study
of GSH synthesis was small-five HIV-
infected volunteers and five healthy ones.
But researchers used an in-depth meth-
od, amino acids tagged with stable iso-
topes, to measure GSH synthesis. Farook
Jahoor, USDA-ARS Children's Nutrition
Research Center at Baylor College of
Medicine, Houston, Texas; phone (713)
798-7084, e-mailfjahoor@ bcm. tmc. edu.
( '.- ".
RoadCrest, a new crested wheatgrass
selected for rhizome development, finer
leaves, and shorter stature, is under evalu-
ation near Logan, Utah.
New Grass To Hold the
A new erosion-fighting grass may
appear on western roadsides and high-
ways within afew years. RoadCrest crest-
ed wheatgrass tolerates cold and drought
and readily forms rhizomes-horizontal
underground stems that send up new
shoots. RoadCrest was developed over
15 years of studies by scientists with ARS
and Utah State University. Tests in four
states indicate it should thrive in temper-
ate, semiarid areas of Intermountain and
western Great Plains states. In these re-
gions, it is best suited where summer tem-
peratures are mild and annual
precipitation ranges from 10 to 20 inch-
es. Compared to many other crested
wheatgrasses, RoadCrest greens up ear-
lier in spring. It requires less seed to es-
tablish a good stand and forms rhizomes
more vigorously. RoadCrest also is short-
er-a trait that helps reduce the need for
mowing. The new grass is descended from
plants grown from seeds collected in
Turkey. Seed should be on sale by 2000.
Kay H. Asay, USDA-ARS Forage and
Range Research Unit, Logan, Utah;
phone (435) 797-3069, e-mail khasay@
Could Stave It Off
ARS researchers have blazed a short-
cut to identifying soybean lines that can
stand up to the soybean cyst nematode.
They did this by developing a super strain
of the wormlike pest that they keep con-
fined in a lab for studies. The nematode
has caused woe to growers since its dis-
covery in 1954 in North Carolina. Now
found in most soybean-producing states,
it causes greater losses than all other soy-
bean pathogens combined. It ruined near-
ly 220 million bushels of soybeans in
1997. Further, the nematode has consis-
tently overcome whatever resistance has
been available in commercial soybeans.
Today, the Hartwig cultivar developed
by the University of Missouri is the only
commercial bean resistant to all nema-
tode races known to be in farmers' fields.
The researchers' new approach is aimed
at having a remedy available on the inev-
itable day when Hartwig-resistant nema-
todes begin appearing in fields. In
greenhouse tests, the scientists bred 30
generations of nematodes on Hartwig
plants. This resulted in a strain capable of
feeding-and reproducing-on this or-
dinarily highly resistant cultivar. Special
precautions keep the new nematode strain
safely confined. Researchers will use it
as a test population to get a bead on soy-
bean lines that may hold promise as new
sources of natural resistance. Lawrence
D. Young, USDA-ARS Crop Genetics and
Production Research Unit, Jackson, Ten-
nessee; phone (901) 425-4741, e-mail
Agricultural Research/January 1999
U.S. Department of Agriculture
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