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The Promise of
Dolly, a sheep unremarkable
except for her origin, has caused us to
stop and think.
Dolly, as the world knows, is the
sheep cloned at Scotland's Roslin
Institute. Since the formal announce-
ment of her existence, there has been
an intense public debate over the
ethics of cloning both animals and
humans. What hasn't been heard is
the thinking behind Dolly's creation.
The scientists at Roslin Institute
have conducted research for many
years to produce rare drugs in the
milk of sheep and cattle. That re-
search was sparked by a U.S. Depart-
ment of Agriculture study that
showed new genes, including human
genes, could be inserted into sheep,
pigs, and rabbits.
Some dozen years after this USDA
study, the research at Roslin has
begun to pay off. The Roslin
scientists introduced into sheep a
modified human gene that promotes
production of the human protein
alpha- 1 antitrypsin.
The Roslin scientists found that the
human gene functioned in sheep and
caused alpha-1 antitrypsin to be
produced in the sheep's milk. The
Scottish biotechnology company PPL
Therapeutics has purified the human
protein from the sheep milk and is
testing it as a drug for the treatment
After seeing the power of this
technology for alleviating human
pain and suffering, many researchers
sought support to conduct similar
research on genes that produce other
rare human proteins. Scientific
reports indicate that human proteins
for several blood clotting factors and
for one antibacterial protein have
been produced in animals' milk.
USDA's investment in research to
understand genes and how they work
appears to have produced an early
payoff in biomedicine.
Dolly represents a new approach
to inserting genetic information into
animals. How does this new ap-
proach improve on the method
reported by USDA?
In the earlier method, genes were
injected into eggs. But the success
rate was low. Less than one out of a
hundred eggs would ultimately
produce an adult animal with the
inserted gene. Meanwhile, the
investment in surrogate mothers for
the 99 eggs that didn't carry the new
gene made the research expensive.
In contrast, Dolly was produced
from cells grown in the laboratory. In
theory, if a new gene had been added
to those cells, then all of Dolly's
cells would have carried the new
gene. Experiments are under way to
test this assumption.
Returning to the issue of the
benefits of cloning-will we produce
much of our lean meat from clones?
It seems unlikely, at least for a while.
Producing Dolly was expensive and
Also, we must protect the genetic
diversity of our food-producing
animals so they can respond effec-
tively to challenges such as emerging
diseases or climatic change. If all
animals were genetically identical,
they would all have the same
It is possible that with appropriate
germplasm conservation programs,
we can design farm management
programs to maximize the consistent
qualities of a set of clones.
We in USDA's Agricultural
Research Service expect to put the
methods that produced Dolly to a
variety of uses. For example, they
might help us learn more about the
genes behind whether an animal uses
food to make muscle or fat and about
the genes that control a cow's level
of resistance to mammary gland
infections. They will aid the study of
methods to make milk an even
healthier food for people-especially
infants-and there will be other
studies that we have yet to envision.
Just as the basic research at USDA
was the predecessor to Dolly, the new
research made possible by Dolly will
ultimately pay off in many ways, for
animals and people alike.
Caird E. Rexroad, Jr.
ARS Gene Evaluation and Mapping
Laboratory, Beltsville, Maryland
KEITH WELLER (K5783-81
Animal physiologist Caird Rexroad
inspecting bovine embryonic cells.
Agricultural Research/May 1997
Vol. 45, No. 5
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the Agricultural Research Service, U.S.
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Agricultural Research Service
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With IPM, Bigger Areas Are Better 4
Heterophils to the Rescue! 9
Potatoes, Once Again, Under Fungal Attack I 0
A Close-up Look at White-Speck Neps in Cotton I 4
Assessing Air Quality Around Cotton Gins 1 7
Trickle-L Spreads Irrigation Know-How 1 8
Weed Control on the Central Plains 19
Fuzzy Logic for More Rational RDAs 20
A Breakdown of Cultural Barriers 21
Helping Honey Bees Fight Mites 22
Science Update 23
Cover: Agricultural Research Service
entomologist Brad Higbee (left) explains
the benefits of areawide insect pest
suppression to Jerry Wattman, manager
of this apple orchard near West Parker
Heights, Washington. Photo by Scott
Researchers can boost chicks'
immunity within hours of hatching.
(Story on page 9).
Agricultural Research/May 1997
Codling moth, the most
destructive pome fruit
pest, worldwide, is finally
meeting its match.
That match is a 5-year program in
the western United States. Now in its
third year, the Codling Moth Area-
wide Suppression Program aims to
suppress this pest over wide growing
areas, so that fruit growers can
"It works," says Carrol 0. Calkins,
an Agricultural Research Service
"The principal way we control the
moth is through the use of synthetic
female sex pheromone that growers
place in orchards at a rate of 120 to
400 dispensers per acre," says
Calkins. "The pheromone so confuses
males that they can't find females.
"This ARS-developed mating
disruption technology for codling
moth control is most efficient when
insect populations are low. So some
judicious amounts of insecticides are
sometimes needed at the beginning of
the growing season to lower moth
populations if they are high," he says.
Because of codling moth and some
concern as well about other minor
insect pests, apple and pear growers
in the western United States spray
their crops with nearly 2 million
pounds of insecticides annually.
Unchecked, codling moths have the
potential to destroy an estimated 80
percent of the Northwest's apple crop
and 50 percent of its pears. Since
most consumers won't accept the
occasional worm in the apple,
growers and fruit packinghouses lose
money if infestation rates are high.
But growers want to cut back their
use of pesticides, which cost from
$60 to $150 per acre. There's also the
Entomologists Alan Knight (left) and
Carrol Calkins examine Golden Delicious
apples for codling moth damage. Photo by
Scott Bauer (K7617-12).
risk that codling moths will become
resistant to currently registered
insecticides. And less insecticide use
allows natural enemies to attack
codling moth and other orchard pests.
"We're extremely pleased with
results so far," says Calkins. "Grow-
ers are getting excellent control of
codling moth, with sharp reductions
in pesticide use and fruit damage."
SCOTT BAUER (K7618-15)
Golden Delicious apples are the second
most popular apple in the United
States after Red Delicious.
Calkins works at the agency's
Yakima Agricultural Research Labor-
atory near Wapato, Washington.
In addition to mating disruption
and insecticides, growers have other
weapons. They can infect the insects
with bacteria or spray infected trees
with petroleum oils that coat and kill
the insects. The growers can also
release factory-reared sterile males
that later mate with wild females,
rendering the subsequent eggs sterile.
"We also released parasites that
attack codling moths on small re-
search plots," says Thomas R. Unruh,
ARS entomologist at Wapato. "Up to
1,000 per acre of Mastrus ridibundus
and Liotryphon caudatus (Ichneu-
monidae) were released on trees in
late summer. As a result, up to 60
percent of overwintering codling
moths were parasitized by the time
they emerged the following spring."
John Biele, a grower who is part of
the areawide program in northern
Washington, is pleased, too. "We
reduced by about half the amount of
insecticides applied for codling moth
control last year, compared to our
needs before the program began,"
says Biele. "This year, we plan on
using none or very little. It seems to
be working, and lots of people are
excited about the progress."
Scientists and grower/cooperators
started the areawide program in 1995
with about 2,800 acres of apple and
pear orchards at five sites.
Last year, acreage was expanded
to include some 3,700 acres. This
year, another 4,000 acres and five
new sites were added.
Each site differs in climate,
topography, fruit varieties, and pest
densities. Each also has different
combinations of secondary pests
including leafrollers, leafminers,
leafhoppers, lygus and stink bugs,
and various mites and aphids.
This site next to the U.S.-Canadian
border involves 14 growers and 378
acres. The area previously harbored
large populations of codling moths
and required frequent insecticide
applications during the growing
season. After just 2 years in the
program, some orchards didn't need
any sprays. Overall fruit damage was
only 0.04 percent last year, down
from an already low 0.2 percent the
first year of the program. Credit the
release of sterile male codling
Agricultural Research/May 1997
moths-coupled with pheromones
that disrupted mating-for reducing
the subsequent need for insecticides.
"We found it's best to release the
sterile males from late June into
September and to aim for a ratio of at
least 40 to 1 of sterile to wild males,"
says ARS entomologist Alan L.
Knight, who is also at Wapato. "But
because wild populations were so low
last summer, sometimes our release
ratio averaged 180 to 1. With each
succeeding generation in a sterile
release program, the ratio should
continue to increase."
Leafroller populations decreased
as well. In the caterpillar stage, these
insects feed on fruit and leaves. The
resulting damage makes the fruit
unmarketable. Growers participated
in a thorough early-season monitor-
ing and spraying program that
included one chemical and one oil
spray and two or more applications of
Bacillus thuringiensis (Bt) spray.
This bacterium produces a protein
that paralyzes the intestinal tracts of
Amount of leafroller-damaged
fruit by the end of the second year
was about half that experienced by
growers not in the program-0.5
percent versus 0.9 for growers using
Howard Flat, Chelan, Washington
All but one of 36 apple and pear
growers in Howard Flat participated
in the 1,092 acres under study. They
used a hoop to attach pheromone
dispensers containing Isomate-C+ on
upper tree branches to disrupt mating.
Results were impressive. Before the
study began, 0.9 percent of the apples
and pears suffered codling moth
damage. Last year that was down to
0.2 percent damage-even better than
the 0.6 percent damage the first year.
"Of the orchard blocks studied, 70
percent had no damage at all. In
contrast, the one grower who was not
in the program suffered considerable
damage," according to Kelly Denton,
who is the Howard Flat coordinator.
Sampling for codling moth popu-
lations with sticky traps baited with
the lure, Codlemore, indicate when
and if control sprays are necessary.
The numbers of moths captured in
these orchards were reduced by 82
percent from 1995 to 1996.
But leafrollers remained a prob-
lem. Though fruit damage averaged
SCOTT BAUER (K7616-9)
Entomologist Brad Higbee (left) and
technician Chey Temple assess codling
moth damage on Red Delicious apples.
only about 0.2 percent, troublesome
hot spots persisted. Last fall, Denton
sampled bins from different areas in
the orchards to identify these spots.
This spring, growers used the infor-
mation to begin early control pro-
West Parker Heights, Washington
There are close to 450 acres of
apples and pears in this study area
involving seven growers. In addition
to the Isomate-C+ pheromone
dispenser to disrupt mating, a second
one, Checkmate-CM, was used on
about half the acreage.
Overall, codling moth damage was
reduced at this site too. As at the
other sites, most damage was caused
by the second generation of insects.
"Two orchards actually had worse
damage the second year than the first.
That shows how difficult it can be to
accurately predict problem areas,"
says Wapato entomologist Bradley S.
Higbee. "We even placed the traps
higher in the tree canopy, doubled
their density, and deployed different
types in an effort to get a more
Despite these two damaged
orchards, insecticide sprays were
reduced last year to an average of one
application-down from three the
year before. Almost half the test site
didn't need any spray, while growers
who were not in the program applied
five to six.
Some growers had more damage
from leafrollers than from codling
moth-about twice the levels as
conventional growers. Despite
stepped-up efforts to reduce popula-
tions from the first year's level, they
yielded mixed results. The growers
found it very hard to accurately
monitor overwintering larvae and to
gain control with additional Bt
Pear psylla (the major insect pest
of pears), leafhoppers, and leafminers
didn't pose serious problems for
growers in either of the test years.
The Medford site has 6 growers
with 400 acres under production-up
100 acres from the first year. Most of
the site is devoted to pears, but last
year apples were included for the first
time. The pear growers are using a
"soft" approach that relies on oil in
the growing season and oil plus lime
Agricultural Research/May 1997
sulfur sprays before bloom, in addi-
tion to mating disruption.
Overall, codling moths were well
controlled in 1996, with only 0.04
percent fruit damage at harvest. While
pear psylla and mites were no prob-
lem, leafroller populations concerned
growers. The leafrollers were concen-
trated in certain areas, sometimes in
areas that previously posed no prob-
lem. Lygus and stink bugs were also
problem insects, inflicting more
damage in 1996 than in 1995.
"We are challenged by insect
problems on this site. This year, we
plan to monitor and control what's
happening in weeds and shrubs
surrounding our orchards. We suspect
this vegetation is serving as a reser-
voir or refuge for secondary pests
while control efforts are under way in
the orchards," says Laura Naumes,
who is the site coordinator.
Other current weaknesses at the site
include an inability to correctly pre-
dict codling moth and leafroller dam-
age, monitor natural enemies of the in-
sects, and reliably sample and control
secondary pests like lygus bugs.
Naumes says that while damage to
both test site and nearby orchards not
in the program was nearly the same,
the costs for IPM were lower.
Randall Island, California
In the Sacramento River Delta
region, Randall Island includes 760
contiguous acres of pears, mainly
Bartlett, operated by five growers.
The program here actually began 2
years earlier than at the other sites, in
an attempt to not only control large
populations of codling moths but to
find ways to slow codling moths'
inevitable increase in resistance to
Guthion [azinphosmethyl], the
insecticide of choice for the growers
in the study. This resistance to
Guthion in codling moths was first
detected at Randall Island in the late
During the past two growing
seasons, there was a 71-percent
reduction in pesticide use in orchards
where mating disruption was applied,
compared to conventional orchards.
Fruit damage from codling moths
and leafrollers was limited to less
than 1 percent each. Other secondary
pest infestations remained low as
well. These included pear psylla, the
European red mite, two-spotted mite,
and pear rust mite.
Technicians Bill Greenwood (left) and
Jamie Foster (right) and entomologist
Brad Higbee inspect for damage from
codling moths or other insect pests before
shipping apples to the packinghouse.
Leafrollers have not historically
been a problem for these growers,
but in 1996 their presence necessi-
tated some insecticide applications.
Mites and psylla seemed to be under
control with an application of
abamectin, a commercially available
This year, growers will try a single
application of Isomate-C+ just when
the first generation of codling moths
begins flight. This will be followed by
one application of an organophosphate
spray at the peak of their flight.
Three of the existing sites were
expanded for 1997 (Oroville, Chelan,
and Medford), and five new ones were
added. Four of the new sites are in
Washington (Brewster Flat, Progres-
sive Flat, Manson, and West Wapato)
and one is in California (Ukiah).
"Each new site presents growers and
scientists with a different challenge,"
says Calkins. "For example, oblique-
banded leafrollers are a serious pest at
the Brewster Flat site but not at others.
Some sites are hilly; others, more roll-
ing or flat. Uneven topography makes
it difficult to determine how to place
the pheromone dispensers so the active
ingredient evenly penetrates the tree
canopy to reach all the codling moths."
The ARS scientists continue their
research to resolve additional problems
that have occurred during the Codling
Moth Areawide Suppression Program.
These include nonpesticide control of
aphids, leafhoppers, leafminers,
leafrollers, and pear psylla by use of
insect growth regulators and biological
In addition to ARS, cooperators
include Washington State University,
Oregon State University, University of
California at Berkeley, as well as farm
and pest control advisors, the Washing-
ton Tree Fruit Research Commission,
Washington Apple Commission, and
Winter Pear Control Committee.-By
Dennis Senft, ARS.
Carrol 0. Calkins, Bradley S.
Higbee, Alan L. Knight, and Thomas R.
Unruh are at the USDA-ARS Yakima
Agricultural Research Laboratory,
5230 Konnowac Pass Rd., Wapato, WA
98951; phone (509) 454-6565, fax
(509) 454-5646, e-mail
Agricultural Research/May 1997
The Promise of Areawide IPM
A conversation with Carrol 0.
Calkins, Agricultural Research
Service's coordinator of the Codling
Moth Areawide Suppression Program
in the Western States.
Ag Res: What is areawide insect
Calkins: It's a strategy for control-
ling insect pests on land farmed by
several neighboring growers. Cover-
ing an extensive area is crucial to
minimizing accumulation of insects at
orchard borders, pesticide drift, and
immigration of pests. Otherwise,
when individual growers battle
insects in an unorganized, unplanned
approach, the pests often get the
Ag Res: How large are these
Calkins: That depends on the
commodity and the pest. In the case
of codling moths in apples and pears,
the area may be as small as 400 acres
farmed by just a few growers. For
something like corn rootworm, an
areawide unit may involve thousands
of acres. The size of the area largely
depends on the mobility of the insect
Ag Res: You are working on
codling moth suppression, and you
used corn rootworms as an exam-
ple. Are there any other areawide
ARS programs under way or in the
Calkins: In Mississippi, the
agency is undertaking an areawide
program using a viral disease of the
tobacco budworm, a pest of cotton.
This program began in 1987, and
ARS is now testing the technology on
large geographical areas equivalent to
314 square miles. ARS intends to
initiate one or more new projects this
year, but the pests to be targeted are
still under discussion and review.
Ag Res: Why is there such
interest in these programs?
Calkins: The President has asked
that 75 percent of the United States'
cropland be under integrated pest
management by the year 2000. The
codling moth program, a part of that
effort, will reduce the amount of
insecticide used on apples and pears
while still protecting the crops
through use of economical alterna-
tives. Also, the 1996 Food Quality
Protection Act will limit the amount
of residues allowed on food items.
Ag Res: What methods and
technology are you using to sup-
press codling moths?
Calkins: The key component is
mating disruption. We saturate an
orchard with a synthetic sex phero-
mone that so confuses males in their
quest to find females that few actually
do mate. The result is that fewer
insects are available to infest fruit.
This permits a dramatic reduction in
insecticide use. In turn, the absence of
pesticide has allowed a buildup of
natural enemies that attack secondary
pests of pome fruits-leafminers,
leafhoppers, and aphids.
Ag Res: Have growers come to
accept this technology?
Calkins: When we first explained
the program to growers, most of them
were skeptical. Fortunately, a few
were willing to take a chance and sign
up. All of the growers in the program
are very satisfied with the results and
after 2 years, none have dropped out.
In fact, many more growers in
Washington, Oregon, and California
have now asked to enter the program.
And several in Colorado and Idaho
have also expressed a keen interest in
Ag Res: Has the technology
caught on outside the program
Calkins: Several large and small
growers have tried this on their own.
Large growers were more successful
than smaller ones, because their
acreages were more extensive and
they only experienced some damage
near the orchard edges.
Ag Res: What has motivated
growers to use mating disruption as
part of their codling moth control
Calkins: After the technology was
initially developed in the 1970s at our
laboratory in Yakima, several grow-
ers tried it. But they found an insecti-
cide called Guthion [azinphosmethyl]
was cheaper and easier to use. Later,
codling moth began to show resis-
tance to this chemical in California
and in some areas in Washington. The
growers then needed a new control
technique, and mating disruption was
the most promising.
Ag Res: What are the advantages
of being enrolled in an areawide
Calkins: One is the bringing
together of smaller growers so they
can derive the same advantages of
extensive acreage that large growers
enjoy. Under this program, growers at
the perimeter of the unit are most at
risk from invading insects. We
encourage these growers to get their
immediate neighbors to come into the
program so that the original partici-
pants are no longer on the perimeter.
This areawide approach has become a
bit of a sociological program as well.
Neighbors have found they must
work together to accomplish pest
control, and they have. *
Agricultural Research/May 1997
they're the Royal Canadian
Mounties of the immune
system-the heroes who
show up in the nick of time-and they
take on all bacterial invaders, be they
salmonella, listeria, pasteurella, or E.
coli. They're infection-fighting white
blood cells called heterophils, and
Michael H. Kogut has found a way to
make them do his bidding to protect
young poultry. He is a poultry immu-
nologist in the ARS Food and Feed
Safety Research Unit at College
When bacteria invade the intestines
and try to pass through the intestinal
wall to the bloodstream-gateway to
all the organs-heterophils surround
and devour the invaders. The prob-
lem: The body's mechanisms that put
heterophils into play typically aren't
functional until the host, whether a
child or a chick, is about a week old,
allowing plenty of time for bacteria to
gain a toehold. Kogut says the solu-
tion is natural substances called
cytokines that are produced by white
"We've found a particular type of
cytokine called lymphokine that
causes heterophils to come to where
the bacteria are and devour them,"
says Kogut. "By giving lymphokines
to newly hatched chicks, we're simply
giving the chicks' immune systems a
In tests, Kogut and colleagues have
shown that if day-old chicks are given
lymphokines, heterophils are on hand
within hours to provide the kind of
protection that a bird's immune sys-
tem could take a week to develop nat-
urally. A single dose suffices until the
bird's own immune system kicks in.
"We've done experiments with
lymphokines taken from older birds
that were immune to salmonella and
shown those same lymphokines can
protect chicks against coccidia, the
parasites that cause coccidiosis," says
KEITH WELLER (K3627-16)
Kogut. "This can apparently protect
against anything that's invasive."
Kogut has been working with
cytokines since his research days at
the University of Arkansas at Fay-
etteville. When he joined ARS in
May 1992, the cytokine study came
with him. Kogut and Billy M. Hargis
of Texas A&M University's veteri-
nary pathology department have
collaborated on studies showing
lymphokine injections could signifi-
cantly reduce organ invasion by
Salmonella enteritidis, a type of
salmonella found primarily in eggs.
"We've now worked with S.
typhimurium, S. gallinarum, and S.
arizoni," Kogut notes. "These are all
serologically distinct bacteria, and the
same lymphokines will protect
against all of them."
In hundreds of experiments over 4
years and involving an estimated
5,000 birds, day-old chicks and
turkeys have been treated with
lymphokines, then dosed with up to a
million disease-causing bacteria per
bird. For comparison, other birds
received the bacteria but no protec-
"We usually wait 24 hours, then
check the birds' organs for signs of
salmonella," Kogut explains. "Eighty
percent of the birds that didn't
receive lymphokines have salmonella
in their organs, compared with less
than 10 percent of the treated birds.
"We've developed a permanent
cell line that we can grow in tissue
culture and produce lymphokines in
large quantities," says Kogut. "We
have a cooperative research and
development agreement with Eli
Lilly & Co. of Indianapolis, Indiana,
to develop lymphokine-based protec-
tive products for poultry."
Unlike other products such as CF-
3, a bacterial blend developed at the
College Station lab [See "Natural
Microbes Curb Salmonella," Agricul-
tural Research, November 1994, pp.
22-26.], the lymphokine-based
treatment won't prevent salmonella
and other bacteria from colonizing
the bird's intestines. But it will
prevent the salmonella from hitching
a ride in the bird's bloodstream to
organs such as the ovaries, where
eggs are produced. And it could play
a key role in protecting U.S. poultry
health, Kogut adds.
"Salmonella gallinarum is killing
70 to 80 percent of infected flocks in
Mexico," he notes. "Also, there's a
type of S. enteritidis called phage
type 4 that is killing hundreds of
thousands of chickens in Europe and
China. We've had only small out-
breaks of it, but the potential is here
for a big outbreak. A weapon like the
lymphokines could help us go on the
offensive against getting it here on a
broad scale."-By Sandy Miller
Michael H. Kogut is in the USDA-
ARS Food and Feed Safety Research
Unit, 2881 F&B Rd., College Station,
TX 77835; phone (409) 260-9221, fax
(409) 260-9332, e-mail
Agricultural Research/May 1997
Sn ancient times, farmers
danced, chanted, and even
invoked spells to protect
their crops from the ravag-
es of pests and disease.
Fortunately, today's growers are
armed with more knowledge about
crop diseases and how to control
them. Integrated pest management
and pesticides greatly increase the
odds of winning the war against plant
diseases. But as time has brought
better weapons, it has also brought
more devastating diseases.
"Late blight caused by the fungus
Phytophthora infestans is an excel-
lent example," says plant pathologist/
microbiologist Kenneth L. Deahl,
who is with the ARS Vegetable
Laboratory in Beltsville, Maryland.
"It can destroy a potato crop in a
matter of weeks.
"And new strains of the fungus
that are now attacking potato crops
throughout the world are far more
difficult to control than the strain that
struck in the 1800s," says Deahl.
When this fungal plant disease
attacked Ireland's potato crop, half a
million people starved, and another
million emigrated to North America.
Despite modified cultural practices
and fungicides designed to slow the
blight down, the new, more severe
strains of late blight have spread
throughout the world in just 6 years.
These strains have sexually produced
spores that can live in infected stems,
tubers, and soil over winter and be
infective the next season.
According to Neil Anderson,
University of Minnesota plant
pathologist, the more virulent strains
of late blight produce spores on plant
stems, while the original strains
sporulated only on plant leaves. "In
the 25 years that I've worked with
late blight, I've never seen blight
attack tubers like these new strains
do," he says.
Plant physiologist John Helgeson examines potatoes growing at the University of
Wisconsin's research station at Hancock. [See "Hybrid Potatoes Survive Blight" on page
13.] Resistant to late blight, this hybrid is also being used in breeding trials at the ARS
Vegetable Laboratory, in Beltsville, Maryland.
The new strains of late blight that
have appeared in the United States
are called US-6, US-7, and US-8,
while US-1 is an Al, original strain
that can be controlled with the
Unlike Al, the new A2 strains
aren't deterred by this chemical or by
imperfectly applied cultural practices,
such as immediately culling and de-
stroying infected potatoes.
Since the A2 strains are resistant to
metalaxyl, the Environmental Protec-
tion Agency allowed emergency use
of three other chemicals against the
disease in 1995. Although that
helped, isolated epidemics of new,
aggressive strains of late blight
occurred in 1995 and 1996.
In November 1996, plant patholo-
gist Robert W. Goth and plant
geneticist Kathleen G. Haynes, who
are also based at the ARS Vegetable
Laboratory, released two potato
breeding selections that resist the
most virulent strains of late blight.
In addition, Goth, along with
colleague Judith Keane, has devel-
oped a way to test potato leaves for
resistance to late blight. Up till now,
the only way to find out how well a
plant would do was to infect it in
field plots and watch for symptoms.
This procedure risked spreading the
highly contagious blight throughout
an entire test area.
"Because late blight had been
controlled with chemicals since the
middle of the 20th century, breeding
for resistance to the disease was not
a top priority in the United States,"
says Haynes. "And all major potato-
producing areas of the United States
had a blight forecasting and chemi-
Agricultural Research/May 1997
cal spray program based on weather-
oriented models. The fungus thrives
in cool, damp weather."
U.S. Department of Agriculture
efforts to breed potatoes for race-
specific resistance to the disease
began in the 1920s. And former ARS
plant breeder Ray Webb began the
ARS Vegetable Laboratory's breed-
ing program for field resistance to
late blight in 1976.
"The two resistant breeding
selections that we released were the
result of three generations of plant
crosses," Haynes says.
"Initially, this germplasm had
shown resistance to the severe strains
of late blight found in the Toluca
Valley, Mexico, but it did not have
other characteristics needed to be
When grown in the field, the
plants produced irregularly shaped
potatoes that wouldn't process well
into chips or fries. Since Haynes and
Goth weren't increasing the level of
resistance to the disease with succes-
sive breeding, the scientists decided
to release the germplasm to other
breeders, who they hoped would
combine desirable processing and
fresh-market characteristics with the
late blight resistance in the two ARS
Last year, Haynes gathered 17
potato clones that were reported to
have some resistance to late blight.
From them, she produced virus-
tested plantlets in tissue culture so
that minitubers could be distributed
to State scientists at eight U.S.
locations. The clones came from
research programs by ARS, univer-
sity (Cornell, Minnesota, and Colo-
rado State), and European sponsors.
Haynes worked with scientists
from the Universities of Florida,
Maine, Minnesota, and Wisconsin,
and from Michigan State, North
Dakota State, Penn State, and
Cornell Universities. They evaluated
the level of resistance at each loca-
tion and ranked the clones from 1 to
17, with 1 being the most resistant to
late blight and 17, the least.
"Of the top four clones that
showed the most blight resistance,
three came out of Beltsville and one
from the ARS potato breeding
program at Aberdeen, Idaho,"
Haynes reports. "We only released
two of the Beltsville clones and plan
more work on the third."
Neil Anderson and his University
of Minnesota colleague, Vergel
Concibido, field-tested the clones.
"Since we've only had the A2
strain in Minnesota for the last 4 or 5
years, we tested the new clones at
our Rosemount Agricultural Experi-
ment Station, which is 80 miles from
Plant pathologist Ken Deahl examines a
potato damaged by late blight fungus.
To ensure continuing availability of this
valuable food staple, plant breeders must
unite desirable processing and fresh-
market characteristics with late blight
Agricultural Research/May 1997
our potato-growing region," Ander-
son reports. "The new material
showed good resistance to the disease
and stayed green when other clones
were dead from blight. We also had
good results from the clones devel-
oped at Aberdeen."
Anderson and Concibido planted
the experimental clones close to
Norchip, a commercial chipping
potato variety, and inoculated Nor-
chip with the severe strains of late
blight so the fungus could spread
naturally. Anderson reports several
important findings from the research.
"Even though some of the clones
we evaluated are somewhat suscepti-
ble to the disease, they would still
require less chemical sprays than
commercial varieties," he says.
"This would save growers money
and also help cut down on the amount
of chemicals released into the
Roger Jones, extension plant
pathologist at the University of
Minnesota, says that the major
problem in trying to control new
strains of P. infestans is that preven-
tive spraying of pesticides is neces-
sary about every 5 days. Historically,
he says, growers sprayed for blight an
average of once or twice a season,
and that spray regimen worked. But
for the new strains, even increasing
the number to 8 or 10 applications
doesn't always work. So not only are
growers incurring more costs, they're
putting more chemicals into the
environment and still losing.
Late Blight Economics
Just how devastating are these new
strains of late blight?
The International Potato Center in
Lima, Peru, estimates late blight
losses at about $3 billion annually
SCOTT BAUER (K5455-7)
Potatoes infected with
late blight are purplish
and shrunken on the
outside, corky and
worldwide. In the United States,
losses over the past several years are
estimated in the hundreds of mil-
lions. Potato growers in Washington
and Oregon alone lost $30 million
in 1995, says Cornell University
plant pathologist William E. Fry.
"A good example is a single
potato grower in New York who lost
$1 million to the new strains of the
disease in 1994," says Fry. "Despite
a doubling of pesticide expendi-
tures, the disease cut that grower's
marketable yields by 80 percent. In
addition to defaulting on three
supply contracts, the grower had to
dispose of 4,090 metric tons of rotting
potatoes in an environmentally
acceptable way. Needless to say, he is
no longer growing potatoes.
"The rate at which these exotic
strains of P. infestans spread and the
severity of the epidemics they pro-
duce are astounding," Fry says. "The
new strains appeared in the eastern
United States beginning in 1992. By
1996, immigrant strains had become
established in most of the United
States and Canada."
Test Quickly Measures Resistance
A test developed by Goth and
colleague Judith Keane could help
slow the onslaught. It can determine
in just 6 days if a plant can resist the
original-as well as exotic-strains of
late blight. In addition to potato
plants, it works on tomato plants,
which are also a victim of late blight.
By simply detaching leaves from
plants and subjecting them to the
pathogenic fungus, the scientists can
tell if a plant has resistance.
"Testing late blight resistance of
plants in a field requires introducing
the pathogen and chancing the risk of
infecting an entire growing area,"
Goth says. "Our test can be conducted
on individual leaves in a greenhouse
or in a lab. The detached-leaf tech-
nique is not plant destructive, and
leaves from the same plant can be
used to test for other pathogens."
Unlike field testing, this method is
not weather-dependent and can be
done at the convenience of the plant
breeder or researcher.
Potato growers worldwide anxious-
ly seek some relief from this seeming-
ly invincible foe. "Having resistant
breeding selections and a way to test
disease susceptibility are a start,"
Goth says. [For an earlier story on late
blight, see "What Was Around Comes
Around," Agricultural Research, May
1994, pp. 4-7.]-By Doris Stanley,
Agricultural Research/May 1997
Kenneth L. Deahl, Kathleen G.
Haynes, Robert W. Goth, and Judith
Keane are at the USDA-ARS Vegeta-
ble Laboratory, Bldg. 010A, 10300
Baltimore Ave., Beltsville, MD
20705-2350; phone (301) 504-7380,
fax (301) 504-5555, e-mail [Goth]
ARS plant geneticist Kathleen Haynes
and plant pathologist Robert Goth have
released two potato breeding selections
that resist the most virulent strains of
Can you name America's No. 1
fresh vegetable on a pounds-per-
person basis? Answer below.
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Hybrid Potatoes Survive Blight
Combining the genes of a wild Mexican potato species with those of
U.S. commercial potatoes can provide a measure of resistance to the
devastation caused by late blight, says John P. Helgeson. He is a plant
physiologist in the ARS Plant Disease Resistance Research Unit at
Using a genetic engineering technique whereby leaf cells of
different potato species are fused together, Helgeson showed that the
wild potato, Solanum bulbocastanum, could be crossed with commer-
cially grown potatoes.
The so-called somatic hybrids that were produced proved highly
resistant when exposed to the late blight fungus in test plots in Wiscon-
sin in 1994. Then, in 1995, they were planted in Idaho, Maine, Ne%\
York, North Dakota, Washington, West Virginia, and Mexico. In 1996,
the clinching test was done in a Wisconsin field where the plants grew
well, even without fungicide spraying. The best line, called J103K7,
yielded more than 20 tons per acre.
ARS researchers at Beltsville and Aberdeen are now using this line
to further develop new varieties.
In Madison, Helgeson and ARS plant geneticists are using a method
known as polymerase chain reaction (PCR) to map resistance to late
blight in S. bulbocastanum. They are using DNA fingerprinting to find
pieces of DNA that will allow plant breeders to determine before
planting if seedlings are likely to be resistant.
In three different crosses between S. bulbocastanum and commercial
potatoes, the researchers found a piece of DNA and used it to identify
resistance with 95 percent accuracy. This accomplishment should
greatly speed development of new resistant varieties because breeders
will be able to determine right away whether or not resistance is
present in seedlings.
Helgeson presented information about late blight resistance at the
January 1997 North American late blight workshop sponsored by
USDA's Cooperative State Research, Education, and Extension
Service and ARS in Tucson, Arizona.-By Linda Cooke, ARS.
John P. Helgeson is in the USDA-ARS Plant Disease Resistance
Research Unit, Department of Plant Pathology, University of Wiscon-
sin, Madison, WI 53706; phone (608) 262-0649, far (608) 262-1541, e-
Agricultural Research/May 1997
Laundry equipment has come a
long way since the Maytag Gyro-
foam rescued our great-grandmoth-
ers from labor-intensive agitators
and wringers in 1922.
As washing technology has
advanced, so have the tools of textile
science. Take microscopes as a case
The scanning electron microscope
(SEM) was developed in 1942 and
has been commercially available
since the early 1960s. It uses elec-
trons to scan a sample's surface and
form images, in much the same way
a television does. This microscope
allows researchers to look at fiber
providing valuable information
about morphological structure.
Wilton R. Goynes used an SEM
to confirm that small, undyeable
clumps of cotton fibers-known in
the textile industry as white-speck
neps-are the result of underdevel-
oped cotton. Goynes is a chemist in
the Cotton Fiber Quality Research
Unit at ARS' Southern Regional
Research Center (SRRC) in New
His finding proved what re-
searchers had suspected since the
1940s. For under an SEM, white-
speck neps appeared as mats of
ribbonlike material, giving research-
ers proof of their origin.
Cotton fibers are usually made up
of a thin primary cell wall and a
thicker secondary one. It's the
secondary wall that gives the fiber a
rounded, tubelike shape and makes
for easy dyeing. Without that sec-
ondary cell wall, the fibers look
flat-like the ribbons that are re-
vealed by the SEM.
Cotton grading systems such as
HVI (high-volume instrumentation)
can track neps, but not all neps
produce white specks. Technically,
neps are tangles of fiber. A tangle of
mature fiber can still take up dye.
Underdeveloped cotton fiber magnified
It's just the tangles of very immature
fibers that become undyeable white-
"The white-speck problem actual-
ly comes from the field, when plants
or growing conditions don't allow
the fibers to mature properly," says
Goynes. "Neps can sneak up on
mills: The money is spent to dye the
fabric, and it comes out spattered
with white specks where the dye
Bales of high-quality cotton can
be blended with lower grades to use
more of the cotton crop. However, if
a bad growing season produces bales
with a large number of undeveloped
fiber clumps, blending cannot solve
Now Goynes' verification that the
white-speck neps are really the result
of underdeveloped fibers allows him
and other researchers to focus on
solutions. Some will involve improv-
ing conditions in the field.
Others will be directed toward
detecting immature white-speck neps
before they reach the dye bath. For
example, since the clumps of undye-
able flat fibers reflect light differently
from mature cotton, Goynes says
there may be a way to use special
lighting to detect these immature
fibers before money is wasted on
trying to dye them.
In a recent paper, Goynes, Patricia
D. Bel-Berger, Eugene J. Blanchard,
and other SRRC cotton researchers
tracked white-speck neps from the
field through processing, including
their occurrence in dyed and enzyme-
treated fabrics. It won the American
Association of Textile Chemists and
Colorists' top prize in last year's
Inter-Section Technical Paper
The paper was full of new re-
search. For example, Blanchard, who
is a chemist in SRRC's Cotton
Textile Chemical Research Unit,
reported on enzyme pretreatments
that could help reduce the number of
Goynes and Blanchard explored
whether enzymes such as cellulase
can modify undeveloped fibers to
improve fabric dyeability. Even with
cotton varieties that were prone to
white-speck neps, Blanchard saw
reductions of 33 percent.
It's not enough that fabric dyes
well. Consumers also want lasting
color for their clothes. Detergent
makers now add enzymes to reduce
pilling, but there is a risk of fading
the color and weakening the fabric.
Agricultural Research/May 1997
Materials engineer Patricia Bel-Berger and chemists Bill Goynes (center) and Eugene
Blanchard examine scanning electron micrographs (SEMs) that show the structure of a
The electron microscope lets
researchers see fiber wear long
before consumers can-so industry
can choose treatments that keep
clothing looking good and lasting
longer. It also helps chemists like
Blanchard prove that experimental
enzyme treatments are effective in
controlling neps. And, Blanchard
found, some dyes may work better
with enzymes than others.
"There are various dyes for cotton,
including direct and reactive classes,"
he says. "Since reactive dyes chemi-
cally bind to fabrics, their colors stay
true with enzyme detergents. Some
direct dyes, which are just positioned
within the fiber structure, may fade
after several washes. It also appears
that some dyes-both direct and
reactive-actually limit enzyme
damage," Blanchard adds.
Bel-Berger, a textile engineer in
the SRRC's Cotton Fiber Quality
Research Unit who also worked on
the award-winning paper, has found
that mechanical processing can play a
role in white-speck nep control.
Cotton mills clean and straighten
fibers using a process known as
carding, in which the fiber is run
through a large drumlike roller with
combing wires. Most mills use two
carding cylinders-to perform
Bel-Berger's surprising find was
that when cotton has lots of underde-
veloped fiber neps, single carding is
better than tandem carding, which
tends to open and separate the white-
speck neps, making the problem
appear worse. Her image analysis of
dyed fabrics showed tandem-carded
white-speck neps to be larger and
more numerous than single-carded
ones and to result in a higher percent-
age of white on the dyed fabrics.
Bel-Berger is now working with
industry collaborators to confirm her
results. If the findings prove true,
mill operators can pre-test their
cotton and process it accordingly.
For the Good of the Environment
All this research is good news for
it allows for less wasted material and
a higher quality product. But textile
makers, like all other industries, have
to also be concerned about their
impact on the environment.
The scientists at SRRC are looking
for new ways to process cotton that
are kinder to the environment. And,
as with white-speck nep control,
SEMs provide scientists another way
to look at this problem.
"Cotton fibers come from the plant
with waxes, pectins, and proteins on
their surfaces. Mills have to remove
waxy materials to dye fabric," says
Goynes. "But the alcohols and
chlorinated solvents once favored by
industry are now restricted because
of environmental concerns. We'd like
to see if biodegradable enzymes can
do the job-and using electron
microscopes is one way to find out."
Another example of how Goynes'
work with SEMs has benefited the
Agricultural Research/May 1997
environment is his study of non-
woven fabrics. These materials are
often used in disposable cloth prod-
ucts such as diapers, moist tow-
elettes, and personal care products.
Consumers fill U.S. landfills with
them, so these products need to be
Goynes and coworkers found that
cotton degraded faster than synthetic
materials often used in these dispos-
able products. He was able to con-
firm this, because electron micros-
copy allowed him to see and assess
the s-peed and degree of decompoil-
lion o\er time.
Much has been done with fiber
research, thanks to the electron
microscope. But light microscopes,
which normally have a maximum
magnification of 1,000 times, also
have a place in Goynes' laboratory.
Sometimes those lower-tech tools
reveal things the more advanced
Meanwhile, other SRRC scientists
use SEMs not only for cotton re-
search, but for projects on rice,
peanuts, and corn as well.
Scanning electron micrograph shows a
coiled cotton fiber with flattened, twisted
areas that formed as the fiber dried.
Magnified about 65x.
Technology advances are not
stagnant. Newer instruments, like the
atomic force microscope, are being
used by the center. These scientific
tools have their own special advan-
tages and will lead to more discover-
ics in the future.-By Jill Lee, ARS.
Wilton R. Goynes, Eugene J.
Blanchard, and Patricia D. Bel-
Berger are at the USDA-ARS
Southern Regional Research Center,
1100 Robert E. Lee Blvd., New
Orleans, LA 70179
[Goynes] phone (504) 286-
4483, fax (504) 286-4419, e-mail
i 'goynes @nola.srrc.usda.gov
S [Blanchard] phone (504) 286-
. 4495, fax (504) 286-4271, e-mail
S [Bel-Berger] phone (504)
286-4455, fax (504) 286-4419,
L e-mail bel-
Scanning electron micrograph of a white-
speck nep in a typical plain-weave cotton
fabric. Magnified about 125x.
Agricultural Research/May 1997
Assessing Air Quality Around Cotton Gins
otton ginners are beginning
to face opposition from
when they undertake construction of
new gins to remove valuable fibers
from cotton seed.
But, Agricultural Research Service
engineers at USDA's Southwestern
Cotton Ginning Research Laboratory
in Mesilla Park, New Mexico, are
showing that gins are not a threat to
"We've tested a commercial,
handheld meter to measure the
particle concentration coming out of
exhaust air from gins. This is the first
time such an instrument was shown
to provide reasonable measure-
ments," says engineer Ed Hughs,
who is at the Mesilla Park laboratory.
"Called HAM, for handheld
aerosol monitor, it was previously
used to measure dust inside process-
ing plants like textile mills. It gets a
reading by measuring how much
light is scattered as a beam hits
HAM can provide rapid field
measurements without the need for
costly laboratory analysis of hand-
collected air samples. As a result of
this research, the instrument has the
potential to be used by industry
engineers to monitor and evaluate
changes or improve-
ments in their gin -
concern are particles
that are less than 10
diameter. That's about one-seventh
the diameter of a strand of hair.
These tiny, nearly invisible dusts
known as PM-10 are so light they can
stay suspended in air for a long time
and are thought to pose respiratory
health risks to susceptible individu-
als. PM-10 concentrations can reach
high levels in congested cities,
industrial areas, construction sites,
and some farming communities.
The ARS engineers have modified
the two most popular gin emission
control devices known as the 2D2D
and 1D3D cyclones. While these
devices enable cotton gins to meet
most regulatory requirements, air
quality standards are becoming more
stringent. So improvements are going
to be needed.
Using 12-inch-diameter models in
their lab, the engineers devised modi-
fications to the inlet and body
designs that made the cyclones more
efficient than current models. Some
commercial-size units 36 inches in
diameter are now being built and
Since some people feared gins
emitted high levels of hazardous
materials like arsenic, lead, and
mercury-elements found in soil that
clings to cotton bolls-the scientists
also determined exactly what materi-
als gins emitted from their processing
systems. They used both
proximate and X-ray
analyses that disclosed very low
levels of these elements-as well as
16 other elements-coming from gins
in Alabama, Arizona, Arkansas,
California, Georgia, Mississippi,
Missouri, New Mexico, South Caro-
lina, Tennessee, and Texas.
"None of 19 elements tested for
occurred at levels of any concern in
meeting federal clean air regulations
established by both the U.S. Environ-
mental Protection Agency and the
U.S. Department of Labor's Occupa-
tional Safety and Health Administra-
tion," says Hughs.
The scientists concluded the only
emission of concern was inert parti-
cles-cotton leaves, stems, and fibers,
as well as soil particles-with diame-
ters of 10 micrometers or less, of
which cotton gins are generally a
minor source compared to many other
industries.-By Dennis Senft, ARS.
Ed Hughs is at the USDA-ARS
Western Cotton Ginning Research
Laboratory, P.O. Box 578, 300 East
College Dr., Mesilla Park, NM
88047; phone (505) 526-6381, fax
(505) 525-1076. *
This commercially built monitor has
the potential to rapidly measure dust
around cotton ginning operations by showing
how much light is scattered as a beam hits dust
particles in the air.
Agricultural Research/May 1997
Trickle-L Spreads Irrigation Know-How
,. eed a fast, easy, inexpensive way to get an
answer to a question about drip-irrigating i
orchard, field, golf course, or garden?
Try the Internet discussion group called Trickle-L
"If you post a question in the morning, you're like
start getting answers from experts all over the world
just a few hours," says ARS agricultural engineer Th
J. Trout. He directs the ARS Water Management Re-
search Laboratory in Fresno, California, where Trick
was launched in 1994.
Trout says Trickle-L users include about 500 grow
scientists, extension agents, and irrigation equipment
manufacturers-and likely some greenhouse manage
landscapers, and amateur gardeners as well. Most arc
from the United States, though experts from about tmw
dozen other countries also belong to this "virtual con
nity" on the Internet.
Trickle-L is what is known as a "mailing list"
(also listservv"), or subject-specific group. When a
member of the group posts a message, that
communication is automatically sent within a few
minutes to the e-mail address of all other members.
"It's somewhat like a 24-hour electronic post
office," says Richard M. Mead, who created
Trickle-L while a soil scientist at the Fresno
laboratory. Now a cooperator, Mead did the work
with the aid of Jerome Pier, who was then at the
University of Nebraska-Lincoln.
Trickle-L gets its name from the aboveground
and underground (buried) drip-irrigation systems
that deliver precise amounts of water to plants via
tiny microsprayers or through emitters that squeeze
out water a drop at a time.
For some crops, especially high-value fruits and
vegetables such as strawberries or broccoli, drip or
trickle irrigation frequently brings bigger yields
and higher profits than better known irrigation
techniques like furrow systems or overhead
sprinklers. And buried-drip irrigation is being tried
on alfalfa in California, cotton in Texas, and corn in
Kansas-crops not traditionally irrigated this way.
"Admittedly," says Trout, "drip irrigation can havi
higher installation and maintenance costs. But the tec
nology gives growers an unparalleled degree of preci
in delivering water and fertilizer-or other farm cher
cals-to plants. That saves water and prevents over,
fertilizers that might otherwise leach into underground
Trickle-L users incur no cost to join this cyberspace
club, other than the expense of an Internet connection
Trickle-L, Trout says, is "gaining a reputation as one
of the best places on the Internet to go to for friendly,
well-informed help with problems of setting up and
running drip-irrigation systems."
Users of Trickle-L have turned to other members for
advice on everything from how to stop gophers from
gnawing on buried irrigation tubing to how to set up the
most cost-effective drip system for watering raspberries
Trickle-L, adds Trout, gives scientists at the Water
Management Research Laboratory, and at other ARS labs
as well, an inside look at the everyday problems growers
and irrigation managers face.
"It's one of the fastest ways for us to learn about new,
real-world issues," he says. "That helps us improve our
SoH CUt away to expose a arip irrigation line in a tomato nelw.
What's more, Trickle- L serves as a forum for scien-
tists' theoretical discussions on topics like evapotrans-
e piration-plants' use of water.
;h- In addition to Trickle-L, the Water Management
sion Research Laboratory also provides two other Internet
mti- resources-Salinity-L and a World Wide Web site.
se of Salinity-L is a discussion group for growers, research-
id ers, and others who want to exchange ideas on how to
cope with-and forestall-buildup of salts on arid
,e farmlands. Salinization is a natural process that irrigated
n farming inadvertently accelerates.
Agricultural Research/May 1997
Richard W. Soppe, a visiting scientist with the Fresno
laboratory, established this specialized group in 1995, in
collaboration with Charles Sundermeier, a computer
systems manager at the University of Nebraska-Lincoln.
"Both the Trickle-L and the Salinity-L discussion
groups," Trout notes, "have increased the Water Manage-
ment Laboratory's visibility worldwide."
The laboratory's WWW site has also garnered new,
international attention for the research center. It is an
award-winning site. It lists recent publications from the
laboratory staff, describes computer software available
from the researchers, and highlights experiments under
way at the lab's network of study sites throughout central
and southern California.
Microirrigation Forum, newest in the cluster of elec-
tronic irrigation information sources, was started in 1996
by Mead. "Microirrigation," he explains, "is the term
used internationally to describe drip or trickle irrigation."
Still maintained by Mead, the forum lists other
irrigation-related Internet sites; announces forthcoming
meetings, conferences, and seminars; and archives some
of the most useful discussions, called subject threads,
Internet users often refer back to Trickle-L discussions
as the best source of information that might not be readily
For example, an agronomist with one of the country's
largest manufacturers of drip-irrigation equipment has
frequently sent growers a copy of a 1996 Trickle-L
discussion that explains how to correctly flush chlorine
through irrigation tubing. The procedure kills bacteria or
algae that could otherwise clog tiny emitters.-By
Marcia Wood, ARS.
Thomas J. Trout is at the USDA-ARS Water Manage-
ment Research Laboratory, 2021 S. Peach Ave., Fresno,
CA 93727; phone (209) 453-3101, fax (209) 453-3122, e-
To subscribe to Trickle-L, send an e-mail message
containing the words Subscribe Trickle-L followed by
your first name then last name (do not use a subject line)
To join Salinity-L, send an e-mail message with the
words Subscribe Salinity-L followed by your first name
then last name (do not use a subject line) in the body of
the message to email@example.com
To visit the ARS Water Management Research Labora-
tory web site, enter http://asset.arsusda.gov/wmrl/
To browse the Microirrigation Forum, enter http://
on the Central Plains
There's an axiom in the weed control business: The more
closely related weeds are to the crops they infest, the harder
it is to stop them. That's because growing conditions that fa-
vor the crops often also favor the weeds. And chemicals that
kill the weeds often as not also kill the crops.
Agricultural Research Service agronomist Randy L.
Anderson has come up with some new ways to control prob-
lem weeds in winter wheat and other crops grown on the
Central Great Plains. A few of these weeds-volunteer rye
(rye that escaped harvest and sprouted the next season),
jointed goatgrass, and downy brome-have been reduced by
up to 75 percent in his studies near Akron, Colorado.
Anderson found that timing of nitrogen fertilizer place-
ment can help growing wheat more than it helps downy
brome. Usually, farmers apply fertilizer at seeding time, a
practice that benefits both wheat and weeds. But if fertilizer
is applied about 5 months before planting, wheat can get
ahead of the downy brome. That's because wheat roots
extend deeper into soil than those of downy brome and can
extract fertilizer that's moved a couple of inches down.
Then, because the wheat is taller, downy brome grows in its
shade and loses more of its ability to compete.
Two other practices make it more difficult for downy
brome. Switching to a taller wheat like Lamar, rather than
growing the more traditional shorter varieties like Tam 107
and Vona, also cuts sunlight to the weeds," says Anderson,
who is at ARS' Central Great Plains Research Station. And
seeding 65 pounds of wheat seed per acre rather than the
current 40 pounds results in more shading, too.
These easy-to-use farm practices reduced growth of
downy brome by 40 percent and, likewise, its weed seed pro-
duction. Following the technique for two growing seasons
cut this weed population by 75 percent. In other tests using
these same practices, Anderson reduced jointed goatgrass
and rye populations by 35 percent.
Anderson says farmers will experience some yield reduc-
tions, because taller wheat varieties don't produce as much
grain as shorter ones. But, he adds, if growers get their weed
problems behind them, they can switch back to shorter vari-
eties and then come out ahead.
Additional research shows that crop rotations also play an
important role in reducing annual weed problems. Adding a
summer annual crop like corn or sunflowers to the tradition-
al winter wheat/fallow scheme lengthens the time before the
next wheat crop. This allows farmers a chance to apply her-
bicides that kill weeds but do not affect the summer annual
crop.-By Dennis Senft, ARS.
Randy L. Anderson is at the USDA-ARS Central Great
Plains Research Station, P.O. Box 400, Akron, CO 80720-
0400; phone (970) 345-2259, fax (970) 345-2088, email
Agricultural Research/May 1997
Fuzzy Logic for More Rational RDAs
I t controls Japanese subways, air-
conditioning systems, and cam-
corders. And it may one day assist
health professionals in setting objec-
tive Recommended Dietary Allowanc-
es (RDAs) if ARS nutritionist Eric 0.
Uthus has his way.
It's fuzzy logic-a mathematical
approach to problems that can't be
defined precisely, such as how much
of a particular vitamin or mineral an
individual needs to consume each day.
That amount varies, depending on
many factors including the person's
age, gender, heredity, and intake of
other nutrients, says Uthus, a biochem-
ist at the Grand Forks (North Dakota)
Human Nutrition Research Center.
What's more, use of scientific data
to set an RDA requires judgment calls.
For instance, the process poses ques-
tions like: Do we want to saturate
body tissues with enough of the vita-
min to provide a 30-day reserve or a
60-day reserve? There is no specific
number that will satisfy everyone in-
volved in determining the RDA.
"Fuzzy logic enables us to deal
with situations that are not clear-
cut," says Uthus. "It should make
the RDA process more objective."
Uthus teamed up with German
physicist Bernd Wirsam to develop
a prototype for establishing an RDA
for zinc. Co-owner of a company
that uses fuzzy logic to optimize in-
dustrial processes, Wirsam was the
first to apply the method to nutri-
tion. He developed a computer pro-
gram to describe the range of in-
takes of specific nutrients-from de-
ficiency to excess.
The program then calculates,
based on the nutrient composition of
the foods an individual eats over the
course of a week, how closely that
total diet meets all the requirements,
as defined by the German Society of
Nutrition. And it suggests small
changes in the diet that allow the in-
dividual to meet recommendations.
The mathematics of fuzzy logic
were developed in the 1960s by the
chairman of the electrical engineering
department at the University of Cali-
fornia, Berkeley. The Japanese adopt-
ed it in the 1980s to control hundreds
of household appliances and electron-
ics products that must cater to vague
human concepts, such as "the air is
cool." Fuzzy logic defines "cool" in
Unlike classical logic in which
something belongs exclusively to one
set or the other, in fuzzy logic there is
no distinct border separating sets.
Something can belong to two or more
sets-on a binary scale of 0 to 1. But
its membership in all of the sets must
add up to 1.
Uthus explains: "If we asked 100
people what room temperature is
comfortable, we would get a range of
answers. These values would fall into
a bell-shaped curve with, perhaps,
most of the people saying that 70F
was ideal. So the closer the temperature
is to 700F, the greater its membership in
the 'comfortable' set. But while 70F
may be comfortable to the majority, it
may be too cool to some and too warm
to others, giving it partial membership
in the "cool" and "warm" sets.
Likewise, when volunteers are given
a particular vitamin or mineral in grad-
ed amounts, there is no definite border
where one intake is deficient and a
slightly higher intake is adequate. It's a
range of values. Wirsam uses fuzzy
logic to convert these ranges into a sin-
gle number, says Uthus, who provides
nutritional data and expertise.
A Grand Forks colleague helped to
select two fairly sensitive biochemical
indicators to use in developing the pro-
totype curve for zinc. The amount of
zinc in red blood cells is a good indica-
tor of zinc deficiency, he says, because
it falls off rather quickly as intake de-
creases. For the other end of the curve,
zinc excess, they used the activity of
Agricultural Research/May 1997
Health -- -
DeathI I I r
0 5 10 15 20 25 30 35
Zinc Intake, mg/day
FUZZY LOGIC CURVE FOR ZINC CONSUMPTION
[Shows relative health status of individuals with varying intakes of zinc]
superoxide dismutase in red blood
cells. This enzyme requires a balance
of copper and zinc to function prop-
erly, so its activity drops when zinc
intake is excessive.
Wirsam uses these findings to de-
scribe fuzzy sets based on five in-
takes: zero intake, minimum intake-
the least amount needed to prevent
deficiency, optimum intake-the
amount that confers the most health,
safe upper limit-the most that can
be consumed without causing any
toxicity, and toxic intake.
Using this method, the researchers
came up with a zinc RDA of 9 milli-
grams per day. That's well below the
15 mg recommended for adult males
by U.S. and German committees but
close to a 1993 recommendation by
Europe's Scientific Committee for
Food, says Uthus.
"Intuitively," he notes, "9 mg
looks good when considering the
fuzzy logic curve [see diagram] be-
cause this intake is at the peak, or op-
timal level, of the curve, while the
recommended value of 15 mg is not."
Uthus emphasizes, however, that
the recommendation is based on
scanty data and is meant to demon-
strate the principle of using fuzzy
logic to set RDAs.
"The model I envision," he says,
"is one in which variables could be
easily added as new information
comes to light. A highly developed
model could be used to study how
other nutrients interact with a given
vitamin or mineral to alter its require-
ment."-By Judy McBride, ARS.
Eric 0. Uthus is at the USDA-ARS
Grand Forks Human Nutrition Re-
search Center, P.O. Box 9034, Uni-
versity Station, Grand Forks, ND
58202-9034; phone (701) 795-8382,
fax (701) 795-8395, e-mail
A Breakdown of Cultural Barriers
Scientists in the ARS Corn and
Soybean Research Unit at Wooster,
Ohio, have developed a novel way to
cut out the insect middleman in their
research with corn viruses. They've
pioneered a method for transmitting
viruses to plants directly, without
using insects as vectors.
"There are many technical and
economic advantages to being able to
transmit viruses without using
insects," says plant pathologist
Raymond Louie, Jr. Development of
the method was a necessary step for
research progress, he says.
Previously, plant viruses such as
maize streak and maize rough
dwarf-which inflict millions of
dollars worth of damage on corn
crops in developing countries-could
only be studied by using vectors such
as leafhoppers and planthoppers.
These insects transmit and spread the
viruses naturally when they feed on
Until recently, scientists have had
to obtain, breed, and maintain
specific insects known to serve as
vectors of the viruses they've wanted
to study. This complicated the
Some insects could not be brought
into the United States, thus prohibit-
ing research on some viruses. Other
insect vectors had to be cultured in
the laboratory, which is an expensive
and labor-intensive process.
Scientists at Wooster experiment-
ed with a variety of transfer methods
that not only delivered the plant
viruses to the plant host, but allowed
the researchers to isolate a specific
virus and reduce the risk of contami-
nation by other viruses.
"We often have a problem in
studying viruses because insects may
carry and transmit more than one
type," says Louie. "With manual
transmission, we can be sure we are
infecting the corn plant with a known
virus. This capability offers us the
opportunity to study the effects of
infection by either a single virus or a
mix of viruses"
Using insect pins mounted on an
ordinary engraving tool, ARS re-
searchers have been able to success-
fully transfer all major corn viruses
into mature corn seeds that were first
presoaked for about 2 hours in water.
The tool vibrates the pin, which is
pushed through a drop of virus and
into the seed's vascular system.
When done properly, this allows the
virus to enter the corn embryo within.
Scientists say bypassing insect
vectors will allow them to more
easily isolate viruses for characteriza-
tion, help them to determine the
virulence of a particular virus without
contamination from other viruses,
and lead to more accurate identifica-
tion of resistant germplasm.-By
Dawn Lyons Johnson, ARS.
Raymond Louie, Jr., is in the
USDA-ARS Corn and Soybean
Research Unit, Ohio Agricultural
Research and Development Center,
1680 Madison Ave., Wooster, OH
44691; phone (330) 263-3836, fax
(330) 263-3841, e-mail
Agricultural Research/May 1997
Helping Honey Bees Fight Mites
Here's a surprisingly simple and practical tactic.
I f honey bees would build smaller cells-the six-
sided cubbyholes that are a hive's basic architectural
units-these beneficial insects might better with-
stand devastating parasitic mites.
"Commercial beekeepers nationwide have lost about
half their hives over the past several years to infestations
of tracheal mites that originated in Europe and varroa
mites from Asia," says ARS entomologist Eric H.
Erickson. "The 1990s have been even harder for feral, or
wild honey bees. A combination of mite attacks and the
harsh 1996 winter killed up to 90 percent of feral honey
bees in some parts of the country."
"Cold weather kills honey bees, and bees already
stressed by parasites are especially vulnerable," says
Erickson, research leader at ARS' Carl Hayden Bee
Research Laboratory in Tucson, Arizona.
Tracheal mites lodge in the breathing tubes of adult
bees, suffocating them, while varroa mites suck blood
from both the adults and pupae. Tracheal mites were first
spotted in this country in 1984, varroa mites in 1987.
"During the winter of 1995-96, we had both colder than
normal winter temperatures and widespread mite infec-
tions," Erickson says. "My own backyard was affected. I
used to see bees on my citrus trees, but I didn't see any
buzzing around last summer."
Erickson's research team has found improved honey
bee survival through several research strategies. The latest
is to get the bees to build smaller than usual cells to rear
their young and store
their young and store JACK DYKINGA (K7585-1)
honey in. w
The scientists did
this by installing in
the hive sheets of
starter cells that are
smaller than those
typically used by
cially managed honey
bees use these starter
cells as a blueprint for
building their honey-
comb. With wax they
selves, they form
thousands of cells to
create the many floors K
of the honeycomb. Although the 22-percent smaller size o
right cannot easily be seen, the tighter
The smaller the starter bees better survive varroa mite infesta
cells, the smaller the
cells the bees them-
"We've seen a 40-percent survival rate in varroa mite-
infected hives equipped with honeycombs that have the
smaller, more natural-sized cells that bees would create on
their own," says Erickson. "Hives with the larger commer-
cial starter cells died out.
"Through experiments, we've learned that honey bees
survive a varroa mite infestation better if they have combs
with a diameter 22 percent smaller than what we've used
in the past."
Although the reason why this happens isn't clear yet,
Erickson suspects that building smaller cells may be easier
on the bees, so they can better cope with the stress of a
In nature, bees build honeycombs that appear shelter
skelter. But at the turn of this century, beekeepers learned
how to harvest more honey by providing bees with a
frame containing a wax base. Bees build onto this base to
form a tidy honeycomb that beekeepers easily remove to
harvest the honey. Today, beekeepers align up to 10
frames in a hive.
Honey bees pollinate crops worth about $10 billion
annually. If it weren't for bees carrying pollen from male
flower parts to female parts, there wouldn't be any apples
or almonds. Other crops like some citrus and strawberries
could have their yields slashed by as much as half.
ARS scientists at Tucson are seeking to identify
beehives that appear to have escaped the mites. If further
studies determine that the bees in them are naturally
resistant, the queens
W N could form a genetic
base for developing
strains of bees.
are also working on a
long-term study of
bees' immune re-
sponse to mite at-
Eric H. Erickson is
at the USDA-ARS
Carl Hayden Bee
2000 E. Allen Rd.,
Tucson, AZ 85719;
rter honeycomb cells on the
re natural spacing helps honey phone (520) 670-
s. 6481, fax (520) 670-
6493, e-mail ehejr@
Agricultural Research/May 1997
Sweeping Away Weeds
A common farm tool, the sweep
cultivator, can reduce most of the
threat from downy brome in Pacific
Northwest winter wheat fields.
Downy brome and other bromes
infest 14 million acres of western
winter wheat. They rob yields to the
tune of $300 million a year. But ARS
scientists have found that the broad,
flat sweep cultivator-if used right
after wheat is harvested-makes the
field's weed seeds germinate quickly.
Weeds can then be easily killed by
herbicide or cultivation in the fallow
year. Unless forced to sprout, how-
ever, the seeds stay dormant through
winter. They germinate a year later-
when a new wheat crop is planted.
"Sweeping" weeds also helps protect
the soil from erosion. It doesn't
invert soil or chop straw left to shield
the soil surface, unlike some mechan-
ical approaches to weed control.
Frank Young, USDA-ARS Nonirri-
gated Agriculture Weed Science
Research Unit, Pullman, Washington,
phone (509) 335-1551.
Lure Could Stop Gypsy Moths
From Finding Mates
The love life of the gypsy moth-
the worst insect pest of trees in the
eastern United States-may suffer
some aerial sabotage. Scientists are
refining technology for using aircraft
to deliver tiny sex-attractant dispens-
ers to the tree canopy. There, they
would saturate the air with a synthet-
ic form of the female moth's chemi-
cal sex attractant or pheromone. This
would confuse male moths trying to
home in on real females, and the
pests would be unable to produce
tree-defoliating caterpillar offspring.
The dispensers are soft plastic beads
or flakes less than 3 millimeters in
size. They would be used as an
insecticide-free defense against
isolated or low-level infestations of
the pests. In studies, the fake phero-
mone prevented nearly all the moths
from mating. The number of fertile
egg masses on the pheromone-
protected trees was cut by 75 to 100
percent compared to trees in untreat-
ed plots. Earlier versions of the
dispensers wore a sticky coat so
they'd stay attached to tree leaves,
branches, or trunks. But scientists
want to test dispensers without the
coat, to see if this will avoid clogging
the nozzles of plane-borne spray
equipment. In late June they'll test-
spray a nonsticky version of the
flakes over 225 acres of forest in
Augusta County, Virginia. Originally
from Europe, the gypsy moth attacks
many species of trees in a region
stretching from New England west to
Michigan and south to North Caroli-
na. Kevin Thorpe, USDA-ARS Insect
Biocontrol Laboratory, Beltsville,
Maryland, phone (301) 504-5139.
Harvesting guayule at a University of
Arizona test field near Tucson.
Guayule Latex Process Is Licensed
A Philadelphia company, Yulex
Corp., has received a license to use
an ARS-patented procedure for
making hypoallergenic latex from the
rubber of guayule ("why-YOU-lee"),
a native southwestern shrub. Guayule
is known to botanists as Parthenium
argentatum. It's grown experimen-
tally in California, Arizona, New
Mexico, and Texas. But the Yulex
license may signal an important new
step toward making guayule a
commercial crop. It is estimated that
at least 20 million Americans suffer
from allergies to certain proteins in
natural latex derived from rubber of
Hevea brasiliensis, the Brazilian
rubber tree. High-quality guayule
latex may offer a safe alternative for
people with Hevea allergies, accord-
ing to preliminary medical tests. ARS
collaborated in the tests with the
Woodland Clinic Medical Group in
Woodland, California; Rhode Island
Hospital in Providence; and Johns
Hopkins University School of
Medicine in Baltimore, Maryland.
Katrina Cornish, USDA-ARS West-
ern Regional Research Center,
Albany, California, phone (510) 559-
Less July Thirst Means More
Cotton plants yielded 5 to 11
percent more by drinking smaller,
more frequent sips of the same
amount of irrigation water they
would normally get in July. ARS
scientists developed the approach in
California's Imperial Valley. In a 3-
year test, they applied about 1-1/2
inches of water every 5 days in July.
The traditional regimen calls for 3
inches every 10 days or 5 inches
every 15 days. Many people have
thought this necessary to flush away
crop-damaging salts. But the scien-
tists found no salt buildup in the top
6 inches of soil. The frequent July
irrigations also reduced heat and
moisture stress on the plants and
seemed to make them less attractive
to silverleaf whiteflies, major pests of
Southwest cotton. Chang-Chi Chu
and Thomas J. Henneberry, USDA-
ARS Western Cotton Research
Laboratory, Phoenix, Arizona, phone
Agricultural Research/May 1997
U.S. Department of Agriculture
Agricultural Research Service
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Greenbelt, MD 20770
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w- A new high-cholesterol
diet proves just right for rear-
ing beneficial insects, and it
costs less than a hundredth
of the old diet.
w- An arborsphere at
Kearneysville, West Virginia,
sheds some new light on the
causes of fire blight, a
multimillion-dollar disease of
pears and apples.
a Supplementing foods with
folic acid-as will be required
in 1998-may yield unex-
pected benefits by reducing
cardiovascular disease and
strokes in elderly people.