Group Title: Agricultural research (Washington, D.C.)
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Title: Agricultural research
Uniform Title: Agricultural research (Washington, D.C.)
Physical Description: v. : ill. ; 25-28 cm.
Language: English
Creator: United States -- Science and Education Administration
United States -- Agricultural Research Administration
United States -- Agricultural Research Service
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Place of Publication: Washington D.C
Publication Date: April 1997
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issn - 0002-161X

Full Text
. April 1997




. -700-


Prediction for the
Next Millennium
Imagine a day when farmers and
ranchers can sit at their desks, click an
icon on their computers, and estimate
wind and water erosion that could be
expected from each of the ways that
they might manage their land.
Imagine, too, that they could just
as easily estimate the effect of their
land-use decision on the movement of
topsoil, water, and chemicals from
their farms and ranches into the air or
as surface runoff, tile drainage, or
groundwater leaching.
Producer decisions based on
computer-generated if-then estimates
could both optimize real income and
preserve, indefinitely, the natural
resources that production capability
and profitability depend on.
Such decisionmaking is not as far-
fetched as it may seem. Agricultural
producers could make many of these
predictions using ARS natural re-
source models that have already been
developed. And one important part of
such a scenario would be use of
WEPP-short for Water Erosion Pre-
diction Project model.
The WEPP project was conceived
to replace the Universal Soil Loss
Equation, a technology initiated for
use in conservation planning during
Franklin D. Roosevelt's second term.
The equation has been used on nearly
every piece of agricultural land in the
United States and in much of the rest
of the world, as well. To replace such
a venerable technology has been a
formidable undertaking.
WEPP has required more than a
decade of extensive research-from
experiments on soil erodibility to sta-
tistical analyses for equations to pre-
dict peak rate of runoff. In WEPP, we
have married the science of soil ero-
sion to the immense power of the

But to paraphrase Daniel Hillel,
one of the world's foremost soil phys-
icists, what has been done in WEPP is
no different than what scientists have
been doing for centuries. Essentially,
WEPP developers have tried to under-
stand how nature operates in order to
predict the future course of natural
events. These natural events are ero-
sion events. And we predict them us-
ing a computer model.
WEPP will be an important tool to
help managers select the best way to
produce on, and yet protect, a specific
farm or ranch-based on its soil, to-
pography, and climate. It will help
farmers keep their ponds clear and
their ditches free of sediment. It will
help them meet any federal and state
requirements regarding erosion or
sediment yield.
And WEPP will put a scientific
base under the environmental stan-
dards and expectations set by regula-
tory agencies. Not only will this help
ensure development of realistic stan-
dards for producers to meet, it will
make possible more accurate and irre-
futable environmental determinations.
Naturally, the system of climate,
soil, topography, plants, and manage-
ment practices that WEPP models is
very complex. And not only must this
system be modeled accurately, but so
must its individual components. This
complexity is why some foresee
WEPP being used primarily by natu-
ral resource managers and production
consultants-rather than farmers and
ranchers-in the immediate future.
However, continuing software de-
velopments should one day make it
easier for farmers and ranchers to ap-
ply the model themselves. Because ul-
timately, though WEPP is a complex
model, it is intended as an easy-to-use
tool for a wide variety of 21st century
Ideally, I'd like even schoolkids to
one day be able to use WEPP in
projects related to urban construction
and offsite sediment delivery-or in

4-H projects related to agriculture and
the environment. After all, my 10-
year-old grandson can already balance
the managerial choices in SimCity, the
computer game, quite comfortably.
A continuing challenge will be to
make WEPP the user-friendly tool that
it needs to be for maximum utility.
This requires cutting-edge systems and
human-factor engineering, along with
computer science. We're not there
yet-but we're getting there.
As it is, WEPP fits perfectly into
ARS' mission: both improving man-
agement and conservation of precious
natural resources and supporting pro-
grams of other federal agencies.
WEPP integrates scientific knowledge
into a tool that should, in combination
with others, help optimize the twin
goals of resource management and
technology transfer.
Thanks to this and other ARS natu-
ral resource models, our agency is pro-
viding the technology to sustainably
manage the world's land and water re-
sources. Protecting the land becomes
increasingly important as we face the
prospect of having to feed a growing
population on shrinking acreage.
And implementing the new erosion
prediction technology in the WEPP
model comes at a time when other
problems are being approached simi-
larly. For example, a companion mod-
eling project is related to wind ero-
sion. Water quality models have al-
ready been developed and are being
Emphasis now is on bringing these
models together so that they can use
common databases and run under a
common user-friendly interface. The
prospects are exciting.

John M. Laflen
Project Leader, WEPP

Agricultural Research/April 1997

April 1997
Vol. 45, No. 4
ISSN 0002-161X

Agricultural Research is published monthly by
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Research, Education, and Economics
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Agricultural Research Service
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Agricultural Research

WEPP: Spilling the Secrets of Water Erosion 4

Vanishing Ponds Not a Sure Sign of Spring 9

Sap Beetle Has a Nematode Nemesis 1 0

Keeping Fuji Apples Fresh 11

Gentle Sprayer Cuts Pesticide Drift 12

Nothing but a Wasteful Weed 14

Calcium Boosts Fruit Quality 16

Using Heat To Study Ice Damage in Plants 1 8

Plastic Made More Flexible, More Degradable 21

Computer Figures Risk of Rust in Wheat 22

Science Update 23

Cover: Laboratory studies
of hydraulics and erosion
that result from raindrop
splash and shallow flow can
be used to test and improve
WEPP (Water Erosion
Prediction Project) equa-
tions. Here, agricultural
engineer Dennis Flanagan
(left) and soil scientist
Stanley Livingston use a
green dye to measure flow
velocity and observe runoff
patterns resulting from
simulated rainfall. Photo by
Scott Bauer. (K7570-10)

The rice in the cover photo
for the March 1997 issue was
incorrectly identified as a
Japanese variety. It is U.S.
long grain rice. (K7577-1)

Agricultural Research/April 1997


A new multiplatform graphical Windows interface is being developed to support transfer of the WEPP prediction
technology to field users. Computer programmer-analyst Hailiang Fu (left) and agricultural engineer Dennis Flanagan
discuss the design of the watershed top view and profile side view interface screens.

"A nation that destroys its soils destroys itself."
- Franklin D. Roosevelt

FDR's observation is as worri-
some today as it was in 1937. Lester
Brown of World Watch presents
convincing numbers about erosion's
relationship to a shortage of farm-
land. Carol Browner, who heads the
U.S. Environmental Protection
Agency, describes the products of
soil erosion as our greatest water
quality problem.
Soil erosion is indeed a persistent
and serious research problem and,
with its myriad complexities and
variables, one that is terribly difficult
for scientists to accurately measure.
This much is known: Despite
being a world leader in soil conserva-
tion efforts, the United States loses
about 6.4 tons of soil per acre each
year-that's over 3.5 tons to water
erosion and 2.9 tons to wind ero-
sion-from cultivated row-crop

agriculture. This estimate is from the
1992 National Resources Inventory, a
record of the nation's conservation
accomplishments and future program
needs that's compiled by USDA's
Natural Resources Conservation
Service (NRCS).
Globally, soil loss is believed to be
many billions of tons annually. But
exactly how many? From where?
Where do they end up? And what are
the causes of this loss?
"We need new technology to better
assess how much erosion occurs and
how sediment is deposited on land, as
well as a way of accurately determin-
ing the best alternatives to manage
land so as to prevent erosion," says
ARS agricultural engineer John M.
Laflen, WEPP's project leader.
"That is what WEPP-short for
the Water Erosion Prediction

Project-is all about," he says.
"Now, land managers, environmen-
talists, educators, and policymakers
around the world will have a power-
ful new tool to evaluate alternatives
for the control of soil erosion by
water. This evaluation is critical, if
money and effort spent on erosion
control are to be effectively used."
This new generation of soil-
erosion prediction technology is now
available thanks to over 10 years of
ARS research. The team that brought
forth the WEPP model includes not
only dozens of ARS scientists at 25
locations, but cooperators at USDA's
NRCS and Forest Service and at the
U.S. Department of the Interior
(USDI)'s Bureau of Land Manage-
ment (BLM).
Several universities, including
Purdue University at West Lafayette,

Agricultural Research/April 1997

Indiana, have made significant
"WEPP erosion software is
sophisticated, state-of-the-art tech-
nology that simulates or mimics the
hydrologic and erosion processes that
occur on small watersheds or slopes
on hills within those watersheds,"
says Laflen. "WEPP has components
to predict erosion on crop, range, and
forest lands."
The search for a new set of erod-
ibility values began in 1987 as a
cross-country quest. Laflen and ARS
hydrologist J. Roger Simonton led
research teams that traveled across
the United States, conducting experi-
ments on soils from California to
Maine, from Washington, D.C., to
Washington State.
"The scope and size of this opera-
tion," says C. Richard Amerman,
"constituted a landmark effort-
unique in recent decades-to obtain
the geographically distributed set of
field data needed to drive the WEPP
technology." Amerman is the ARS
national program leader for erosion at
Beltsville, Maryland.
"WEPP represents a major step
forward-almost a quantum leap-in
our ability to evaluate alternative
land treatments in terms of their
impact on soil erosion by water," he
says. "WEPP is a real improvement
over previous models because of
advances in our understanding of
how erosion occurs."
For much of WEPP's 10-year
development, Amerman coordinated
the program nationally to see the
model readied for delivery to users.
What is unique about the way
WEPP operates? Unlike previous
technologies that were statistically
pegged to observations at a limited
number of sites, WEPP is process-
based and, therefore, works for all
sites. It emulates scientifically known
physical soil erosion processes and,
thus, is stronger.

Amerman says ARS hydrologist
Leonard Lane provided the vision
that brought process-based hydrology
to the WEPP technology. And he
credits ARS hydraulic engineer
George R. Foster with "giving WEPP
the heart of the technology-the rill
and interrill erosion routines that
drive the model-and laying out in
detail the structure and function of
the model's technology."
Rill erosion is caused by runoff
water flowing over the soil, while
interrill erosion results from raindrop
impact and splash.

their requirements were known at the
outset and that they were part of the
model-building process.
This foresight eventually saved
untold dollars in subsequent retrofits.
ARS agricultural engineer Mark
A. Nearing, who was technical direc-
tor for the WEPP project from 1993
to 1995, led the validation efforts.
"The model has been validated
against about 1,000 plot years of
natural runoff and erosion data from
12 sites, as well as against data from
15 watersheds around the United
States," he says.

Flume experiments can be used to obtain data on soil detachment and transport by
flowing water for use in testing the relationship in WEPP, as well as in development of
prediction equations. Here, ARS scientists Mark Nearing (center) and Dennis Flanagan
(second from left), graduate assistants Dmitry Bulgakov (left) and Viktor Polyakov (right),
and research associate Tingwu Li (second from right) monitor a flume at the National Soil
Erosion Research Laboratory.

As important as the science behind
the model is, if the system is to work,
the needs of the user must be factored
in from the moment the first line of
program code is written. Amerman
feels that Foster's greatest contribu-
tion was bringing representatives of
the agencies that will use WEPP into
the model design process at the very
beginning. Foster made sure that all

"For the first time," says Nearing ,
"we can estimate soil deposition,
sediment yield, how soil loss is
distributed in space and time, to
better target expensive erosion
control measures within the field and
throughout the year."
WEPP includes many interactions
that occur between the environment
and management practices that

Agricultural Research/April 1997

influence erosion, according to Pur-
due hydrologist Reza Savabi, who
worked on many of the model's com-
ponents-including winter and sub-
surface hydrology and water balance.
"These interactions make the
model especially useful in studying
the effects on soil erosion when land
management, climate change, soil
disturbances, and many other shifts
occur," says Nearing. "Its key advan-
tage is that it predicts rill and interrill
erosion separately, which other
prediction tools are not designed to
Agricultural engineer Arlin Nicks,
who recently retired from the ARS
Soil and Water Resources Research
Laboratory in Durant, Oklahoma, de-
veloped the weather and climate com-
ponent of WEPP. Nicks' weather
model, called Climate Generator
(CLIGEN), artificially generates the

Managing the WEPP

During the 12 years of
WEPP's development, three
ARS scientists led the many
researchers and action agency
personnel involved in readying
the model for use.
ARS hydraulic engineer
George R. Foster initiated the
WEPP project and was its leader
from its beginning in 1985 until
1987. Then ARS hydrologist
Leonard J. Lane at the South-
west Watershed Research
Laboratory in Tucson, Arizona,
took over until 1989.
John M. Laflen. an agricul-
tural engineer now stationed at
the National Soil Tilth Labora-
tory in Ames, Iowa, was the last
ARS scientist to lead the WEPP
development project, from 1989
to the present. He supervised
completion of the model and is
currently facilitating WEPP's
implementation by users.

ivncroOoiogist uiane soon ana nyarologist Keza 3avao lOOK at now me intercepuon or
rainfall by crop residue changes the water balance component of the WEPP computer

climate data needed to drive WEPP-
so that the actual weather data from a
site and the data generated by
CLIGEN will have the same statistical
CLIGEN averages climate parame-
ters of the station under consideration
with the parameters of the surround-
ing stations. Results from ARS
computer simulation studies, using
National Weather Service data and the
CLIGEN model, proved consistent
with those obtained using other
prediction tools like the Revised
Universal Soil Loss Equation.
Nearing and Laflen worked with
ARS agricultural engineers Dennis C.
Flanagan and James C. Ascough, II,
in developing and testing the erosion-
prediction technology at the National
Soil Erosion Research Laboratory in
West Lafayette, Indiana. Flanagan
developed the WEPP hillslope profile
model; Ascough, the WEPP water-
shed model.
The combined watershed/hillslope
WEPP program allows users to
simulate runoff, erosion, and sediment
delivery from small agricultural
watersheds or portions of fields in
those watersheds. In addition to work
on the scientific components of the
erosion model, Flanagan and Ascough
also guided first-generation model
interface programs to assist users in
generating and organizing input
information for model simulations.
Systems engineer for WEPP, ARS
computer specialist Charles R. Meyer,
is leading the effort to link the WEPP
model with a new user-friendly graph-
ical interface that "greatly assists
model users in determining input pa-
rameter values, assessing databases,
organizing model runs, and viewing
and interpreting output," he says.
"Graphic information is understood
more easily than numbers, so this in-
terface should make it quicker and
easier for users to enter information
about slope length, incline, soil prop-

Agricultural Research/April 1997

erties, and how the watershed is being
managed," says Meyer, who works at
the West Lafayette laboratory. He is
heavily involved in the effort to link
all ARS erosion models through the
user-friendly graphical interface.
Flanagan was lead editor for the
final WEPP model technical docu-
mentation, user summary documenta-
tion, and a multimedia CD-ROM for
transfer of the technology to users.
"The WEPP95 CD-ROM is one
major tool for transferring the model
to users worldwide," says Flanagan.
"This multimedia disk contains all of
the WEPP software, databases,
electronic documentation, and html
[hypertext markup language] training
The WEPP model technical and
user documentation is available in
several formats and can be viewed
electronically or printed. An html
browsing program is included to
allow viewing of multimedia-text,
audio, video, images-information
on erosion processes, erosion predic-
tion technology and installation, and
use of the WEPP model. The CD-
ROM also contains a 16-minute film
that helps introduce first-time users
to the program.
The CD-ROM can be used to in-
stall WEPP model software with cli-
mate and soils data for all 50 states.
Sets of validation data from natural
runoff plots and sample model input
file sets are also on the disk.
Flanagan was also instrumental in
developing the World Wide Web
pages that allow users to download
WEPP software and learn how to in-
stall and use the erosion model. Most
of the information on the CD-ROM is
available through the Internet.
WEPP software was recently
delivered to several cooperators,
including USDA's Forest Service
(FS) and the BLM. Aware that the
model could be applied to solve
erosion problems that are part of their

missions, these agencies are anxious
to train users. For example, the BLM
hopes to use WEPP to control erosion
on rangelands.
The FS is also champing at the bit.
"We've already trained about 100
people at WEPP workshops around
the country," says William J. Elliott,
who is project leader of engineering
technology for improved forest

access, at the FS Intermountain
Research Station in Moscow, Idaho.
"WEPP allows forest managers to
better address site-specific erosion
problems-like the impact of timber
harvesting on sediment in streams-in
a scientific manner," says Elliott.
"Right now, people make seat-of-
their-pants decisions based on their
experience-without much science be-

A technician times the rate of advance of a harmless green dye in runoff water coursing
thronih furrows during a WEPP field experiment at Tifton. Geornia.

Agricultural Research/April 1997

hind them. Such decisions are not
very defensible in court battles to sup-
port forest-management decisions."
Forest managers can thank the late
Edward R. Burroughs who, as an FS
research engineer at the intermoun-
tain station, adapted WEPP-as it
was being developed-for that
agency's use on roads and disturbed
areas. He ran the same types of
intensive tests on forestlands as
Laflen did on croplands.
Other federal agencies, like
USDI's Geological Survey, are also
eager to reap the model's advantages,
as are numerous consultants, univer-
sity faculty, and researchers at scien-
tific institutions around the world.
David Schertz, national agrono-
mist for NRCS's biological conserva-
tion sciences in Washington, D.C.,
says that his agency views WEPP as
a new generation of erosion predic-
tion technology.
"We plan to implement WEPP-
after appropriate databases have been
developed and tested in the agency-
in conservation planning," says
Schertz. "Its use in such activities,
especially those regarding water
quality, will offer us a new means of
calculating concentrated flow and
routing of sediment from fields."
And WEPP has been demonstrated
to groups worldwide-in Australia,
Austria, Belgium, Brazil, Canada,
China, Costa Rica, India, Italy,
Mexico, Portugal, Russia, Uganda,
and Ukraine. Already, WEPP's been
put to work in an international study
related to global climate change.
A major advancement in erosion
modeling, WEPP has been used on
every continent but Antarctica and
has received extensive testing
worldwide-in Austria, Australia,
Italy, Portugal, and China. Where
specific experimental data have been
available, WEPP has performed well.
These documented data sets were
presented to 150 potential users from

This rainfall simulator and test plot at Cottonwood, South Dakota, enabled technicians to
measure water runoff rates and collect soil samples in a WEPP cropland field study.

federal agencies and institutions at a
special symposium sponsored by the
Soil and Water Conservation Society
in August 1995.
Users can obtain the most current
model release and other information
through the World Wide Web.
"This method of software delivery
is innovative and efficient and allows
for easy updating of information,"
says Flanagan. "Electronic mail is
sent to large lists of WEPP users to
notify them of important updates,
patches, and meetings. Internet users
from the United States and over 50
foreign countries have accessed and
downloaded WEPP information and/
or software. The National Soil
Erosion Research Laboratory's file
server records hundreds of informa-
tion requests each month."-By
Hank Becker, ARS.
Mark Nearing, Dennis Flanagan,
and Charles Meyer are at the USDA-
ARS National Soil Erosion Research
Laboratory, 1196 Soil Bldg., Purdue
University, West Lafayette, IN 47907-

[Nearing] phone (765) 494-8683,
fax (765) 494-5948, e-mail
[Flanagan] phone (765) 494-7748,
fax (765) 494-5948, e-mail
[Meyer] phone (765) 494-8695,
fax (765) 494-5948, e-mail
John Laflen is at the USDA-ARS
National Soil Tilth Laboratory, 2150
Pammel Dr., Ames, IA 50011; phone
515-294-8327, fax 515-294-8125, e-
mail *

Agricultural Research/April 1997

WEPP and supporting
databases. WEPP fixes, WEPP
documentation, and additional
material are available on the
WEPP home page. Access it
at http://

Vanishing Ponds Not a Sure

Sign of Spring

N ow you see it, now you don't.
The disappearance of ponded meltwater in the
field may not be as accurate an indicator of
spring thaw as generations of farmers have believed, say
ARS scientists in the Soil and Water Management Re-
search Unit at St. Paul, Minnesota.
Using sophisticated measuring devices and microwave
technology, the researchers are studying the effects of
freezing and thawing on soil and how winter conditions
affect chemical infiltration and water quality. Measuring
the disappearance of snowmelt in Minnesota fields gives
them clues about the permeability of frozen soils.
"We've been studying the hydrology of frozen soils for
about 6 years," says ARS soil scientist John Baker.
"We've learned some new things about soil properties in
winter. For instance, we'd always assumed a frozen soil
was impermeable-that very little water could penetrate
it-but we find that's not always true."
Using a time domain reflectometer to measure the
liquid water content of soil, the scientists can monitor the
extent to which a soil is frozen.
"Soil doesn't freeze in one large block," Baker ex-
plains. "It freezes in a progressive pattern, with larger
pores freezing before smaller ones.
"This means there is always some liquid water present
in the soils around here. But in very coarse sandy or grav-
elly soils, this wouldn't be true."
The traditional spring thaw heralded by the disappear-
ance of ponded water in fields is a bit decei k in,, n .a
Baker. "In early spring, when the snow
begins to melt, the initial
meltwater often refreezes where -'.
the snow and soil meet, blocking
the penetration of additional
water. Excess snowmelt then
flows across the surface of the soil
to low spots in the field, forming '
temporary ponds.
"At this point, the story gets more
complicated," says Baker. "As
thawing continues, a point is reached
at which the ponds drain rapidly-
often in less than a day. But this
doesn't mean the soil underneath the ..
pond is completely thawed.
"Our measurements indicate that a
substantial layer of the soil beneath the
pond, a zone as thick as 16 inches, can still
be frozen at the time these ponds disappear.
The water is apparently moving through

large cracks and voids in the root zone, quickly reaching
the subsoil below."
The implications of water movement in frozen soil are
important, Baker says.
"Because water moves across the surface of the soil to
meltwater ponds, it means farmers should avoid spreading
manure during the winter. The nutrients in it are likely to
drain into these ponds and subsequently be carried to the
groundwater," he says.
The loss of water from spring thaw also drains the soil
of important spring moisture reserves.
"This meltwater that drains to ponds and rapidly infil-
trates could be used by crops if it could be kept in place in
years when fall moisture recharge is minimal," says Baker.
Scientists think their finding may lead to a changeover
to tillage practices that tend to avoid ponding and leave
more moisture in the soil.
"Farmers may want to identify ponded areas in their
fields in the early spring and make changes in fall tillage
patterns to maximize moisture storage," says Baker.-By
Dawn Lyons-Johnson, ARS.
John M. Baker is in the USDA-ARS Soil and Water
Management Research Unit, University of Minnesota, 439
Borlaug Hall, St. Paul, MN 55108; phone (612) 625-4249,
fax 612-649-5175, e-mail jbaker@ soils.umn. edu *

Melting snow forms a temporary pond in this no-till corn
field near Rosemont, Minnesota. Recent studies show that
snowmelt water often infiltrates, even while the soil beneath
is still frozen.

Agricultural Research/April 1997

A newfound species of
nematode may be part of
the solution to controlling
a familiar and costly corn pest: the
sap beetle, Carpophilus lugubris.
Agricultural Research Service sci-
entists discovered the elongated,
threadlike nematode, Psammomermis
nitiduesis, living in sap beetles col-
lected near Illinois cornfields in 1992.
But only female nematodes could
be reared from the first infected sap
beetles culled from the fields.
Finally, scientists successfully reared
the first males in 1995, enabling the
species to be officially cataloged.
Patrick F. Dowd, an ARS ento-
mologist in the Mycotoxin Research
Unit at the National Center for
Agricultural Utilization Research in
Peoria, Illinois, says that 80 percent
of the sap beetles taken from the
field in early spring were infected
with the new nematode.
"The sap beetle can be a major
sweet corn pest," says Dowd. "It can

be as economically important as corn
earworms and corn borers in some
areas of the Corn Belt."
It also spreads toxic fungi to crops
like field corn. The black, quarter-
inch-long adults feed on corn plant
residues left in the field after harvest,
Dowd explains.
"This residue often contains the
spores of Aspergillus and Fusarium,
which are fungi that not only damage
crops but produce toxins harmful to
humans and animals."
Later, when growing corn plants
pollinate, adult sap beetles fly to them
and spread the fungal spores as they
feed on fresh pollen that falls into the
corn plants' leaf axials.
The fungi grow and thrive in the
warm and moist environment created
at the leaf axials. Their colonies
become a ready source of spores that
passing beetles or caterpillars can
pick up and transport to the corn ear
when they feed on the kernels. And
sap beetle larvae, which resemble fly

maggots, move deep into corn ears,
damaging sweet corn and rendering
it unacceptable to consumers.
Scientists believe the P. nitiduesis
nematode enters the body of the
beetle in late summer, when beetle
larvae are pupating in the soil. The
nematode is large-about 20 times
as long as the sap beetle, Dowd says.
"It is somewhat surprising the beetle
can survive for as long as it does
with this large parasite inside it."
Scientists are studying ways to
move infected sap beetles into areas
where P. nitiduesis doesn't exist, so
the nematode can be used as a
biological control agent.-By Dawn
Lyons-Johnson, ARS.
Patrick F. Dowd is at the USDA-
ARS National Center for Agricultur-
al Utilization Research, 1815 N.
University St., Peoria, IL 61604;
phone (309) 681-6242, fax (309)
681-6686, e-mail *

Agricultural Research/April 1997







C onsum-
ers are
ing more variety
in their fruit and
vegetable choices.
So the apple
industry is providing an
to the more traditional v
Red Delicious and Goldi
Consumers seem to b
pay more for exotic vari
Fuji, an apple that origin
Japan in the early 1960'
only recently caught the
consumers around the w
Production of Fuji apj
ly expanding in Washin
1992, Washington grow
about 805,000 boxes of
years later, their product
to nearly 3.5 million box
pared to all other variety
periencing the greatest a
pension and growth.
"Fuji is an excellent f
apple. It's juicy and flav
retains its texture during
says James P. Mattheis,

Keeping Fuji Apples Fresh

alternative tural Research Service plant physiol- firmness, starch
varieties, like ogist based in Wenatchee, Washing- content," says AM
en Delicious. ton. "However, we found it a chal- fruit should hav
e willing to lenge to maintain other aspects of the slight watercore
eties like fruit's quality so as to extend the accumulation ot
iated in marketing period." the apple's core
s but has Studies at the Tree Fruit Research Mattheis foul
eye of Laboratory have led to Fuji apples have poor flavo
orld. that can be stored for up to 9 months overmature fruil
ples is rapid- after harvest without significant and lose their fl
gton State. In losses in quality, says that the be,
ers harvested Mattheis conducted research apples is a CA i
Fujis. Only 3 during six production seasons. He dioxide concent
ion was up found that several field and storage less (Fujis are s<
Les. Corn- factors interact to determine how Fuji with I to 1-1/2 1
es, Fuji is ex- responds to controlled atmosphere 340F.-By Deni
mount of ex- (CA) storage. CA is a fruit industry James P. Ma
technique to keep apples fresh longer. ARS Tree Fruit
resh-market It involves modifying the concen- 1104 N. Western
orful and tration of gases naturally present in WA 98801; pho,
ripening," the air. fax (509) 664-2

an Agricul-

mattheis@ tfrl.a

8 O-5,000 boxes
of Fujis,. Three
years later,
production had
quadrupled to
3.5 million

Agricultural Research/April 1997

"Fuji apples
should be
harvested for
storage based
on changes in
their color,
, sugar, and acid
4attheis. In addition,
e no more than a
, which is the natural
f a sugar solution in

nd that immature fruit
r and color, while
t are prone to decay
avor and texture. He
st treatment for Fuji
n which carbon
ration is 1 percent or
sensitive to this gas)
percent oxygen at
nis Senft, ARS.
ttheis is at the USDA-
Research Laboratory,
n Ave., Wenatchee,
ne (509) 664-2280,
287, e-mail *


The air-curtain orchard sprayer driven by technician Andrew Doklovic uses multiple
crossflow fans to disperse pesticide to apple trees. Under some conditions, the smoother,
gentler flow of air can reduce spray drift by half.

G one-with-the-wind spray
drift from pesticide applica-
tors may blow across neigh-
boring fields and residential areas,
raising concerns about the environ-
ment. It's an old problem that an
ARS-university team hopes to help
solve with new sprayer technology.
ARS engineers Robert D. Fox and
Ross D. Brazee have helped fine-tune
a pesticide sprayer that uses multiple
fans to disperse the chemical. This

helps reduce spray drift and im-
proves accuracy of pesticide deposi-
tion. The crossflow fans provide a
smoother, gentler flow of air. Tests
show the crossflow fan applicator
could halve airborne spray drift
under specific conditions.
"Our overall mission is finding
ways to apply compounds like pesti-
cides more efficiently with regard to
their impact on the environment,"
says Brazee, who heads the ARS

Application Technology Research
Unit at Wooster, Ohio. "You can
have all the effective agents in the
world, but there's still the challenge
of getting them on target."
The research team compared a
prototype of the crossflow fan
sprayer with conventional sprayers
used in most commercial orchards
and nurseries.
Joining Brazee and Fox in the
work were scientists from Ohio State
University's Agricultural Research
and Development Center and Sven A.
Svensson of the Swedish University
of Agricultural Sciences.
Orchard managers growing apples,
pears, cherries, plums, peaches, and
other tree fruits face a perennial
challenge in controlling fruit-eating
insects, fungal blights, and diseases
that cause millions of dollars' worth
of crop losses each year.
Increasing concerns over the
impact of pesticides on the environ-
ment-especially in residential
areas-are behind the push to de-
velop more effective ways to use
pesticides without diminishing their
effectiveness or driving up agricul-
tural producers' costs.
Advances in mechanical technol-
ogy and the introduction of more
compact dwarf or semidwarf hybrid
fruit trees have changed the way
orchard managers approach pesticide
"Dwarf fruit trees are smaller and
more dense than their ancestors,"
Brazee notes. "We have to adjust our
procedures and machines to match
this change."
The conventional orchard air
sprayer is generally tractor-drawn
and includes a cylindrical tank and
large fan to spray the chemical. Air
drawn into the back of the sprayer
directs the flow of spray outward and
upward and creates a large, nearly
180-degree, fan-shaped airjet.

Agricultural Research/April 1997

While generally effective in
depositing spray on and inside the
fruit trees' leaf canopy, conventional
units tend to create more spray
drift-tiny droplets of pesticide-
that can be caught and carried by the
wind. These units also frequently
deposit more chemicals on the lower
part of the tree, resulting in KEITI
less effective use of the
The ARS engineers and
their cooperators conducted
experiments to sample down-
wind residues from use of
conventional sprayers at a
semidwarf apple orchard at
Wooster. They found spray
drift was greatest from applica-
tions to the last one or two
rows on the downwind edge of
the orchard. "That's because Elec
there are no other tree rows to engl
block it," Brazee says. coll
Other weather factors
including humidity, temperature,
windspeed, and wind direction can
also have a profound effect on the
likelihood of spray drift.
Cooperator Svensson brought to
this country two crossflow fan units
that have been available in Europe
for the past decade and more recent-
ly in the United States. Use of two
or more fans allows spray to be
more uniformly distributed over
fruit trees.
The resulting sprayer unit is taller
than its conventional cousin. Svens-
son found that tipping the upper fan
downward improved deposition of
pesticides on the far side of the fruit
trees, compared with spraying with
both fans aimed horizontally.
This not only gave good chemical
penetration into the tree canopy, but
also reduced spray drift into the
"We measured deposits left by
the crossflow fan and compared
them with those left by the

conventional fan sprayer," says Fox.
"We found the crossflow fan's
downwind deposits above tree height
were much less than those from
conventional sprayers."
At heights around 11.5 to 14.5
feet-about 3.25 feet above the top of
the tree canopy-crossflow deposits

;tronic technician Barry Nudd (lett) and agricultural
ineers Ross Brazee (right) and Robert Fox inspect a
section filter from a high-volume air sampler.

were at least 40 percent less than
conventional sprayer deposits.
The engineers also found the spray
drift from the crossflow fan didn't
travel as far downwind as spray did
when applied with the conventional
sprayer. "As we went downwind 195
to 390 feet, we found we had only
about half the amount of material
being deposited when we used the
crossflow fan," Fox says.
"The downward momentum of the
crossflow fan sprayer limits drift
because it limits the amount of spray
becoming airborne," adds Brazee.
"One problem we have witnessed
with conventional sprayers is that the
spray cloud dodges, or goes around
the tree canopy. Some spray actually
goes up and over the trees. The cross-
flow design helps limit this effect."
While changes in technology will
ultimately help orchard and nursery
managers achieve good pest control
with less impact on the environment,
producers must also rethink how they

manage their orchards and nurseries
with several factors in mind, Fox says.
"For instance, there are things they
can do to minimize spray drift simply
by spraying those last two rows from
the outside in, rather than the inside
out," he says.
The introduction of smaller, tighter,
high-yield fruit trees has also
required orchard managers to
pay more attention to integrated
pest management (IPM) and
use of pesticides overall,
Brazee observes.
"Today's fruit trees are less
labor intensive than their ances-
tors, but they require more
management. It's a trade-off for
growers. One of our goals is to
make their job easier by provid-
ing better technologies-with
l less impact on the environ-
ment-without driving up their
costs," he says.
Both researchers acknowl-
edge that weather is the greatest
variable in orchard and nursery
management today. "We are still
conducting experiments and trying to
get the data we need to help growers
make decisions for the most common
conditions they must face," says Fox.
While the air-curtain or crossflow
fan sprayer is commercially available
to growers, ARS researchers are
keenly aware of the cost of replacing
trees and equipment. "We will contin-
ue research on the crossflow fan,"
says Fox. "We're always looking for
the next weather variable to test our
theories."-By Dawn Lyons-
Johnson, ARS.
Ross D. Brazee and Robert D. Fox
are in the USDA-ARS Application
Technology Research Unit, Ohio
Agricultural Research and Develop-
ment Center, 1680 Madison Ave.,
Wooster, OH 44691; phone (216)
263-3870, fax (216) 263-3670, e-mail
Brazee. 1 or *

Agricultural Research/April 1997


Nothing but

a Wasteful


W hat pernicious weed has

eggplant-like leaves
dotted with long thorns,
a golf-ball-sized yellow fruit, and a
pleasant-sounding name? Tropical
soda apple, Solanum viarum Dunal.
This aggressive weed has infested
thousands of acres of pasture and
lawn in the southeastern United
States. It grows to a height of 3 to 6
feet and can be as broad as it is tall.
In spite of its innocuous name,
tropical soda apple is "nothing but a
weed that has found ideal ways to
spread itself in agriculture," says
ARS botanist Charles T. Bryson.
Bryson works at the Southern
Weed Science Laboratory in Stone-
ville, Mississippi. He says the mature
fruit, resembling small apples, is
toxic to humans. However, it is
palatable to livestock and wildlife,
which later drop the fruit's reddish-
brown seeds in their manure.
A single cow pattie can hold up to
150 seeds, and each tropical soda
apple plant can produce more than
50,000 seeds. Unfortunately for
agriculture, the seeds can host several

Cattle avoid tropical soda apple
plants growing in pastures.

plant disease-causing pathogens,
such as cucumber mosaic virus,
potato leafroll virus, potato virus Y,
tomato mosaic, and the potato
fungus Alternaria solani.
First discovered in Glades Coun-
ty, Florida, in 1988, tropical soda
apple has spread in many agricultur-
al and natural areas. Outside of
Florida, tropical soda apple has been
found in Alabama, Georgia, Missis-
sippi, Pennsylvania, North and South
Carolina, Tennessee, and Puerto
Rico. It has also spread into Asia,
Africa, and Central America from its
place of origin in South America-
Brazil and Argentina.
Losses to the Florida cattle
industry related to tropical soda
apple were estimated at more than
$11 million in 1994. Besides crop
damage and losses in cattle grazing
lands, the weed's thorns can prick
workers handling and harvesting
crops. It's also been found to in-
crease the cost of holding cattle over
for several days before shipping out
of state.

Tropical soda apple fruit turns yellow as it

In August of 1995, tropical soda
apple was added to the U.S. noxious
weed list.
Bryson, weed scientist Clyde C.
Dowler at Tifton, Georgia, and plant
physiologist David T. Patterson at
Fort Pierce, Florida, are studying the
weed, checking to see what herbi-
cides kill it-and under what condi-
tions it can survive.

Agricultural Research/April 1997

I-. -a -

Thorny stems and leaves are a nuisance to
workers handling crops infested with
tropical soda apple.

In Georgia, Dowler has set up a
federal-state certified weed contain-
ment facility. He has screened many
broadleaf herbicides for their effec-
tiveness in killing tropical soda
apple. He got good control with
herbicides such as glyphosate,
triclopyr, picloram, and dicamba,
which are commonly used on range-
lands for brush control.

In Mississippi, Bryson says he's
involved in alerting farmers to the
weed's existence and showing them
how to apply herbicides in a timely
manner. He grew tropical soda apple
in a confined area, applying herbi-
cides after mowing the weeds down
to 4 inches. The best control-up to
95 percent weeds killed-was
obtained with triclopyr. [See page 3
for pesticide disclaimer. ]
Tropical soda apple's fruit produc-
tion is greater in Mississippi than in
Florida. "In the Delta soils, we can
expect 8 to 10 plants to produce I
million seeds per year," says Bryson.
"And tropical soda apple can also
vegetatively produce new plants
from root segments, branches, and
old crowns. For these reasons, it's
critical to eliminate both mature and
immature fruit, the whole plant, and
its roots."
Patterson conducted controlled-
environment experiments in the
phytotron at Duke University in
Durham, North Carolina, to deter-
mine factors potentially limiting the
ecological range and agricultural

impact of tropical soda apple. He
concluded that the weed will contin-
ue to invade new areas throughout
the South and lower Midwest unless
current infestations are eradicated.-
By Linda Cooke, ARS.
Charles T. Bryson is at USDA-
ARS Southern Weed Science Labora-
tory, P.O. Box 350, Stoneville, MS
38776; phone (601) 686-5259, fax
(601) 686-5422, e-mail
Clyde C. Dowler is at the USDA-
ARS Georgia Coastal Plain Experi-
ment Station, P.O. Box 748, Tifton,
GA 31793; phone (912) 386-3185,
fax (912) 386-7225, e-mail
dowler@ tifton. cpes.peachnet. edu
David T. Patterson is at the
USDA-ARS Horticultural Research
Laboratory, 2199 S. Rock Rd., Fort
Pierce, FL 34945-3138; phone (407)
468-3081, fax (407) 468-5668. *

Agricultural Research/April 1997

Technician Dwayne Visser applies calcium spray to Granny Smith apples for control of
bitter pit and internal breakdown.

F ruit disorders in apples and
pears once cost the industry
several millions of dollars in
losses annually.
Washington State's rural areas
were especially hard hit. Today,
those orchards produce nearly half of
all apples grown in the United States,
worth around $1 billion each year.
Of the commercial fruit producers
in the Pacific Northwest, most now
spray their apple and pear trees with
calcium chloride or calcium nitrate.
Cost can be as low as 22 cents per
tree per year for labor and calcium.
Some varieties need only 3 or 4
treatments; others, 6 or 7.
This very cost-effective technique
developed by Agricultural Research
Service scientists at Wenatchee,
Washington, reduces incidence of
bitter pit, cork spot, alfalfa greening,
and internal breakdown-four
quality factors that render some
apples and pears unmarketable.
On d'Anjou pear trees, the sprays
increased yield by an annual average
of 16 to 18 percent. They also
reduced the incidence of cork spot
and alfalfa greening.
"Controlling bitter pit disorder in
apples is a major part of our program
here in Washington," says Fred
Valentine. "If we didn't spray
calcium on our apple trees, we'd
have a cull rate close to 50 percent on
some of our newer varieties, like
Braeburn." Valentine is production
manager for Dole Fruit in
Wenatchee, Washington.
"Bitter pit was first recognized
about 100 years ago," says former
ARS plant physiologist J. Thomas
Raese, who is now retired.
"When trees undergo stresses,
such as excessively cold or hot
weather, they sacrifice the current
crop by developing calcium-deficient
fruit and evidently relocating some of
the calcium contained in the fruit

Agricultural Research/April 1997

Plant physiologist Tom Raese checks by hand the firmness of a d'Anjou pear sprayed with

back into trees. This relocated
calcium is enough to pull trees
through stress periods.
"Unfortunately, the trees do not
replenish calcium to the fruit, and
calcium-related fruit disorders
result," says Raese, who pioneered
this research on apples and pears. He
also showed that calcium treatments
were frequently associated with
increased cold hardiness in pear trees.
"I liken this to a 50-year war,"
says George Ing, manager of the
Washington Tree Fruit Research
Commission in Yakima.
"While we've conducted lots of
research, we still do not know exactly
when to apply the calcium. We are
applying it by calendar dates. We
need to look at fine-tuning applica-
tions and learning if we can modify
trees so that they move calcium back
to fruit after stress. But that's a long
way off," says Ing.
The commission has helped fund
the ARS research.

noruicuIlurist txepnen uraKe uses a
texture analyzer to precisely measure the
firmness of a d'Anjou pear.

Despite the need for more study,
Ing says knowledge gained so far has
certainly helped the fruit industry and
benefited rural areas of the state.
When sprays were first tested, some
caused more damage than the diseas-
es themselves.
"I strongly believe in using
calcium spray on my apples," says
Gary Vaughn, a grower in East
Wenatchee, Washington. "I have
trophies to prove my apples are better
than those from neighbors who do
not spray."
Vaughn says the sprays have cut
his cullage rate considerably, and he
gets much higher quality fruit coming
out of storage, ready for market.
"In most instances, in addition to
disease control, calcium applications
during the growing season improve
the firmness, total acidity, and
juiciness ratings of apples," says
ARS horticulturist Stephen R. Drake.
He is following up on calcium spray
research begun about 18 years ago at
the Tree Fruit Research Laboratory at
Wenatchee by Raese and Edward A.
Stahly, another plant physiologist
who is now retired from ARS.
Several different formulations of
calcium are available to orchardists,
with label recommendations specifi-
cally for various fruit crops.
On apples, calcium chloride is
applied at 3-week intervals, June
through August, at the rate of 3
pounds per 100 gallons of water. On
pears, the rate is 1-1/2 pounds per
100 gallons. Larger trees require
more spray per acre for adequate
coverage.-By Dennis Senft, ARS.
Stephen R. Drake is at the USDA-
ARS Tree Fruit Research Labora-
tory, 1104 N. Western Ave.,
Wenatchee, WA 98801; phone (509)
664-2280, fax (509) 664-2287, e-mail *

Agricultural Research/April 1997

Although the drop of ice-nucleating bacteria placed on one
rhododendron leaf (white dot) froze, this infrared image shows that
freezing in the detached, terminal shoot began in the stem and
moved out into leaves and buds.

will tell
you, is
one of
in early spring.
That same glistening layer of
frosted ice that so beautifully catches
the rays of an early-morning sun can
mean death to tender, newly
emerging plant or bud growth.
A sudden spring freeze severely
damaged the peach crop in the
northeastern United States in 1994.
Freeze damage to citrus and tomato
crops often costs growers millions of
dollars and limits supplies, causing
consumers to pay higher prices.
Not very much is known about
how plants freeze, according to ARS

plant physiologist Michael
He says, "Until now, we had
no way to tell which part of a
plant freezes first or when the
ice actually forms. For exam-
ple, on a bean plant, can one
leaf freeze and another not? Do
leaves freeze before the stems, or
vice versa? Does the entire plant
sometimes freeze at the same time?
"Some plants can't recover from
damage inflicted by unseasonable
freezes," says Wisniewski. "The
extent of the damage depends on the
dip in the temperature. But we're not
talking about extreme weather; just
280F to 30oF can be destructive to
new growth.
"Cold temperatures alone don't
usually damage new plant growth,
but ice formation in frost-sensitive
crops can be lethal," Wisniewski ex-

plains. "Plants don't freeze right at
320F. They freeze over a wide range
of temperatures below 320F, depend-
ing on various factors that induce ice
formation. To protect plants, we need
to know where in a particular plant
the ice formation begins and how it
progresses throughout the plant. We
can stop it only if we understand how
it happens."
And he is finding out. Wisniewski
is the first to use a new technology in-
volving heat energy, or infrared, to de-
termine where ice first begins to form
in a plant and at what temperature.
Because small amounts of heat are
released by a liquid as it freezes-
that is, as it changes from a liquid to
a solid-Wisniewski can use infrared
video thermography to watch a plant
freeze and follow the progress of ice
formation throughout the plant.

Agricultural Research/April 1997

Until now, the only way he could
have studied ice formation was by at-
taching thermocouples (an electrical
wire attachment that can pick up a
change in electrical flow) to detect
when a plant had completely frozen.
But thermocouples yield little infor-
mation about the original site of ice
formation or the pattern of damage
caused by freezing.
At the ARS Appalachian Fruit
Research Station in Kearneysville,
West Virginia, Wisniewski has used
this infrared camera system to track
ice crystals as they form in apple,
peach, and pear trees and in bean,
potato, and strawberry plants.
"The procedure is quite simple,"
he says. "We put the potted plants in
an environmental chamber, lower the
temperature at a specific rate, point
the infrared camera at the plants, and
watch the ice form. The process is
recorded on video tape. We can use
computer software to analyze the
video tape to study all stages of ice
One of the surprises that Wis-
niewski encountered with bean plants
was that the nodes-the site where
leaves attach to the plant stem-
hinder ice formation. Ice forms fairly
quickly along the stem of the plant
but slows as it approaches the nodes.
Also, while shoots freeze quickly, ice
formation progresses very slowly into
the roots.
Says Wisniewski, "In peach trees,
we found that even when stems
freeze before the flowers, ice does
not automatically form in the flowers,
as you would think. Current theory is
that once shoots freeze, all flowers
along the stem freeze. But we know it
can be just the opposite. Our work
shows that ice formation in plants is
much more complicated than has
been thought."
The following example of how
thermal imaging works was reported

in the February 1997 issue of Plant
In a cold-room demonstration,
Wisniewski placed a small sample of
ice-nucleating bacteria on one lobe of
a bean leaf and a drop of water on the
other and trained the infrared camera
on the plant. The drop of water ap-
peared black through the camera be-
cause the water temperature was low-
er than that of the leaf. The camera
was set to depict all areas with a tem-
perature below about 290F as black
and areas above 31 F as white.

leaf containing the bacteria," Wis-
niewski reports.
Why is it so important to know
how ice forms when plants freeze?
Plants can survive freezing tem-
peratures by avoiding ice formation,
a process called supercooling. If the
temperature drops too low, however,
the ice crystals that develop will
cause more injury than ice crystals
that form at higher freezing tempera-
tures. Ice forms more slowly at
warmer temperatures, which gives
the plant time to acclimate itself to

Plant physiologist Michael Wisniewski (right) and research assistant Glen Davis use
infrared video thermography to analyze freezing of flower tissues. Understanding how
plants freeze will aid development of crops with better frost resistance.

The drop of bacterial cells began
to freeze first. This started ice form-
ing in the remaining part of the leaf,
which completely froze in 2 minutes
and 25 seconds. From the leaf,
formation of the ice progressed down
the petiole into the stem and through-
out the entire bean plant.
"The drop of water on the surface
of the leaf froze, independently, at
least 2.5 minutes after the part of the

drastic changes. Also, slowly formed
ice crystals are smaller than those
formed more rapidly.
When ice forms slowly, water has
time to escape from plant cells so that
ice forms in the spaces between the
cells, not inside them. A more
sudden, sharp drop in temperature
traps water inside cells, causing ice
crystals to form that burst the cells,
killing them.

Agricultural Research/April 1997

Infrared video thermography showed that a drop of pure deionizedd) water placed on the right lobe of this bean leaf froze more than 2
minutes later than the leaf. A droplet of ice-nucleating bacteria put on the left lobe was the first to freeze, inducing ice nucleation
throughout the leaf.

"If we can figure out just how it all
happens, then we can develop logical
ways to block the ice formation,
either genetically or mechanically,"
says Wisniewski.
"The reason plants in nature
normally freeze a few degrees below
320F is the presence of ice nucleators
such as the ice-nucleating bacterium,
Pseudomonas syringae.
"With the new thermal system,
we're able to study not only this
bacterium, but other external and
internal factors that affect a plant's
response to freezing temperatures,"
Wisniewski says.
Steven E. Lindow, one of Wis-
niewski's collaborators from the
University of California at Berkeley,
has shown that eliminating the
bacteria from plant tissue surfaces
allows plants to protect themselves
from freezing.

Lindow has actually introduced
antagonistic organisms on the surface
of plants that compete for the same
space but don't induce freezing.
Wisniewski says there are other
agents besides bacteria that induce
water to freeze at lower temperatures.
"Plants react differently to tempera-
tures-depending on the environ-
ment, humidity, or even whether a
night is still or windy," he says.
To watch ice freeze in plants,
Wisniewski uses an Inframetrics
model 760 imaging radiometer,
which can visually record ice form-
ing in very small droplets of water
and estimate the surface temperature
of plants. Technology involving
infrared cameras that sense heat is
being used by the Department of
Defense and also by utility compa-
nies to fly over power lines to detect
hot spots, thus identifying potential

problems before they happen. In
industrial boilers, these cameras can
sense a hairline crack that can be
fixed, saving thousands of dollars,
and sometimes lives as well.
"Used in agriculture, thermal
imaging can save growers money,
increase production, and help ensure
consumers a good selection of
produce at a reasonable price,"
Wisniewski says. -By Doris
Stanley, ARS.
Michael E. Wisniewski is at the
USDA-ARS Appalachian Fruit
Research Station, 45 Wiltshire Rd.,
Kearneysville, WV 25430; phone
(304) 725-3451, X320, fax (304) 728-
2340, e-mail *

Agricultural Research/April 1997

Plastic Made More Flexible,

More Degradable

plastic food packaging
materials-even the so-
called biodegradable
ones-that are dumped into the sea or
washed into streams can stay fairly
intact for years. Scientists at the Na-
tional Center for Agricultural Utili-
zation Research (NCAUR) in Peoria,
Illinois, are hoping to see that time
reduced to months, or even weeks.
"We're looking for a way to make
low-cost, extruded plastic into a 'box
lunch' for microbes by incorporating
amino acids," says
M. Stein.
Amino acids are among
the most nutritive sources
of the nitrogen which,
along with carbon, is
essential to microbes that
chew up biodegradable
plastics. And besides
nourishing the microbes,
amino acids could serve as
that, especially in high-
starch plastic, help prevent
brittleness and cracking.
In his research, Stein
used a single-screw
extruder to melt and blend
composites of dried starch 3.
and the conventional
plasticizers urea, sucrose, :
and ammonium chloride.
Then he compared those
blends with ones contain-
ing starch and the amino
acids glycine, isoleucine, V
and proline.
Only proline was
superior to urea in provid-
ing flexibility in concen-
trations up to 29 percent of
the weight of the compos-
ites. However, at low .
based pla


rhomas Stein tests the strength and flexibility of a st
stic sample.

We're looking for a way

to make low-cost,

extruded plastic into a

"box lunch" for

microbes by including

amino acids.

Agricultural Research/April 1997

relative humidities around 20 percent,
the proline composites became glassy
instead of flexible-less than ideal
for making plastics.
Another drawback to using starch-
proline composite is its cost. Al-
though starch currently sells for as
little as 10 cents per pound, proline
costs up to 20 times that amount.
Still, researchers are impressed
enough to want to understand why
proline works so well and outper-
forms the amino acid glycine, which
they thought should work
better. By conducting
further experiments and
using computer modeling
to learn about what makes
a good plasticizer, the
scientists may synthesize
better and cheaper ones
than proline from natural
Then, if dry-blended
starch and plasticizer
ingredients costing less
than a dollar per pound
can be run through the
moist heat and shearing
environment of an extrud-
er, perhaps a plastic could
be formed that does not
need an external nitrogen
source for biodegrada-
tion.-By Ben Hardin,
Thomas M. Stein is at
the USDA-ARS National
Center for Agricultural
Utilization Research, 1815
N. University St., Peoria,
IL 61604; phone (309)
681-6338, fax (309) 681-
6689, e-mail steintm@ *


Computer FiureRi of Rust in Whe

When the winter wheat
planting season ap-
proaches, a farmer in the
Central Great Plains might like to
consult a crystal ball.
Would it be advisable to gamble
by planting the highest yielding hard
red winter wheat variety available-
or a lower yielding variety that better
resists leaf rust fungi?
Anything could happen. But the
weather over the past few months can
provide some clue as to prospects for
a rust epidemic the next spring.
Unveiled last summer is a science-
based computer model nicknamed
"Rusty" to appraise the situation
through the fall and winter and
predict the likelihood of rust in next
summer's crop.
"We developed the model to help
wheat growers make management
decisions in both fall and spring,"
says ARS plant pathologist Merle G.
Eversmeyer, who is based at Manhat-
tan, Kansas.
In the fall, growers must decide
which variety to plant. In the spring,
they must decide whether applying a
fungicide to reduce yield losses from
rust would be worth the expense.
Presently there are no biological
controls to fight rust. But, if such
controls were developed for commer-
cial use, the model could play an
important role in their management,
Eversmeyer says.
It tracks the impact of both locally
produced leaf rust spores surviving
the winter on infected leaves and
spores blowing in from miles away.
To develop Rusty, the researchers
used computers to crunch weather
data gathered over 10 years, along
with data from observations on the
rust fungus over that time.
As seasons change, so does the
importance of different kinds of
weather data. For example, snow

cover, which moderates temperature
fluctuations in infected wheat tissue in
winter and early spring, is more
important than average daily mini-
mum temperatures to the survival of
rust fungi.
Until planting decision time,
rainfall since harvest is a small but
influential variable influencing leaf
rust predictions, says Eversmeyer.
Soil moisture is an indicator of how
much volunteer wheat will spring up
from wheat seeds left in the field
during harvest. Volunteer wheat hosts
fungal mycelium and spores that may
survive until they are able to infect the
newly planted crop.
If spores survive the winter, a local
rust epidemic reducing yield from 2 to
10 percent is virtually certain,
Eversmeyer says.
With each 2-week interval through-
out the crop year, new weather
information along with field observa-
tions on rust inoculum survival are
used to enhance the accuracy of
Rusty's predictions. As spring ap-
proaches and the wheat turns green,

an accurate rust severity prediction
can become most important to
growers. During the following 6
weeks they must decide whether or
not to apply a fungicide, because
spraying later might leave a residue
in the grain.
Rusty runs under MS-DOS on an
IBM-compatible personal computer.
Plans are under way to make it
available on the World Wide Web,
with updates at least every 10 days.
Farmers can start using Rusty by
contacting extension wheat patholo-
gist Robert Bowden, Department of
Plant Pathology, Kansas State
University, Manhattan, KS 66506;
phone (913) 532-6176.-By Ben
Hardin, ARS.
Merle G. Eversmeyer is in the
USDA-ARS Plant Science and
Entomology Research Unit, U.S.
Grain Marketing and Production
Research Laboratory, 111 Throck-
morton Hall, Kansas State Universi-
ty, Manhattan, KS 66506; phone
(913) 532-6168, fax (913) 532-6167,
e-mail *

Wheat plants on the left resist leaf rust fungi, while browning leaves on right show plants
are susceptible to a rust that typically cuts yield 2 to 10 percent.

Agricultural Research/April 1997

Science Update

Bacteria May Provide Biofuel,
Cheap Nitrogen Fertilizer
Some soil-dwelling bacteria may
prove useful for making an inexpen-
sive biofuel or improving the produc-
tion of synthetic fertilizer. These
microorganisms use enzymes-
containing iron or iron and vanadi-
um-to change atmospheric nitrogen
into a form plants can use. Some of
the hydrogen released during this
conversion is not used by the plants,
and scientists say the extra hydrogen
could be collected and used as a
biofuel. In addition, bacteria that use
iron in the conversion process may
yield clues about whether iron has
potential as a catalyst in manufac-
turing ammonium-nitrogen fertiliz-
ers. Currently, producing these
fertilizers requires very high temper-
ature and pressure and, thus, lots of
fossil fuel. An alternative process
could lower the fuel requirements.
Paul Bishop, USDA-ARS Soybean
and Nitrogen Conservation Labora-
tory, Raleigh, North Carolina, phone
(919) 515-3770.

Speediest Cover Crop?
Tropic Sun, a USDA-developed
variety of sunn hemp for the South,
grows to its full 6-foot height in 10
weeks, according to tests by ARS
scientists. Other cover crops, such as
hairy vetch and crimson clover, take
7 months. In the South, sunn hemp,
Crotalaria juncea, can be planted
right after corn harvest to protect soil
from fall and winter storms. And
since it's a legume, it can make
enough natural nitrogen fertilizer for
the next corn crop. Sunn hemp can
also be grown as a high-protein
forage for late summer, when other
pastures slow down. USDA's Natural
Resources Conservation Service

selected Tropic Sun from sunn hemp
lines used for centuries as a green
manure crop elsewhere, mainly
Southeast Asia. People in India make
cloth from the fiber. ARS researchers
in Weslaco, Texas, are investigating
whether sunn hemp fiber can be
turned into paper or has potential as a
supplement for peat moss used to
grow nursery plants. D. Wayne
Reeves, USDA-ARS Soil Dynamics
Research Laboratory, Auburn,
Alabama, phone (334) 844-4741.

A Couple of Drinks a Day Can
Lower Vitamin B
One or two alcoholic drinks a day
can interfere with vitamin B levels,
according to an ARS study of 41 men
and women. Their blood levels of
vitamin B12 dropped when alcohol
made up 5 percent of their daily
calories. Over the long term, compro-
mising B 2 status could impair memo-
ry. Scientists also evaluated the
volunteers' levels of folate. This B
vitamin helps transform an artery-
damaging amino acid, homocysteine,
into a harmless substance. That's
important to health, because high
homocysteine is linked with increased
risk of heart disease and stroke.
Average blood folate levels didn't
drop when the volunteers were
consuming the equivalent of two
drinks a day. But during their alcohol-
free period, folate levels rose and
homocysteine levels fell. These
findings shed new light on an old
question: What causes low B vitamin
status in alcoholics? Some health
professionals have said the cause is
poor nutrition; others, that alcohol
degrades the B vitamins. Both factors
appear to contribute. Judith Hall-
frisch, USDA-ARS Beltsville Human
Nutrition Research Center, Beltsville,
Maryland, phone (301) 504-8396.

Seed's Coat of Many Microbes
Wards Off Rot
Shielding corn seeds with a mix of
helpful fungi and bacteria weakens or
kills fungal pathogens that attack
young corn sprouts. ARS scientists
came up with this way of using a
number of different microbial species
to protect corn seeds from rot diseas-
es caused by Pythium and Fusarium
fungi. The diseases can cut yields 10
to 30 percent. Earlier research
approaches focused on finding one
microbial agent to fight one patho-
gen. But a combination of helpful
bacteria and fungi-isolated from
roots and soil-could guard against
multiple pathogens that may be
present. Some good-guy microorgan-
isms compete with fungal pathogens
for nutrients. Others make antibiotics
that kill or repel the fungi. Still other
microbes are parasites that invade
and consume the fungi. Field tests in
Maryland, Minnesota, Delaware, and
Virginia were conducted by ARS
scientists collaborating with the
University of Delaware, Virginia
Polytechnic Institute and State
University, and a commercial firm. In
one field test in which plots harbored
both Pythium and Fusarium, only
about half the seeds sprouted and
grew to mature plants. But 80 percent
of seeds coated with beneficial fungi
and bacteria grew to full-grown
plants. Seed protected with coatings
of fungicides did no better. The ARS
lab is seeking commercial collabora-
tors to develop the technology.
Robert Lumsden, USDA-ARS Biocon-
trol of Plant Diseases Laboratory,
Beltsville, Maryland, phone (301)

Agricultural Research/April 1997

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* An insect threat to Pacific
Northwest apples may suc-
cumb to biological controls
and judicious amounts of well-
timed insecticides.
a Romosinuano calves born
this spring at the Agricultural
Research Service facility in
Brooksville, Florida, were
imported as disease-free
embryos from Venezuela.
a- Need a fast, easy, inexpen-
sive way to get an answer to a
question about drip-irrigating
an orchard, field, golf course,
or garden? Try an Internet dis-
cussion group called Trickle-L.

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