Group Title: Agricultural research (Washington, D.C.)
Title: Agricultural research
Full Citation
Permanent Link:
 Material Information
Title: Agricultural research
Uniform Title: Agricultural research (Washington, D.C.)
Physical Description: v. : ill. ; 25-28 cm.
Language: English
Creator: United States -- Science and Education Administration
United States -- Agricultural Research Administration
United States -- Agricultural Research Service
Publisher: Science and Education Administration, U.S. Dept. of Agriculture :
Science and Education Administration, U.S. Dept. of Agriculture :
Supt. of Docs., U.S. G.P.O., distributor
Place of Publication: Washington D.C
Publication Date: January 1998
Frequency: monthly[1989-]
bimonthly[ former jan./feb.-may/june 1953]
monthly[ former july 1953-198]
Subject: Agriculture -- Periodicals   ( lcsh )
Agriculture -- Research -- Periodicals   ( lcsh )
Agriculture -- Periodicals -- United States   ( lcsh )
Agriculture -- Research -- Periodicals -- United States   ( lcsh )
Genre: federal government publication   ( marcgt )
periodical   ( marcgt )
Statement of Responsibility: U.S. Department of Agriculture.
Dates or Sequential Designation: Began with vol. 1, no. 1 (Jan. 1953).
Issuing Body: Vols. for Jan./Feb.-Nov. 1953 issued by: Agricultural Research Administration; Dec. 1953-<Sept. 1976> by: Agricultural Research Service; <June 1979>-June 1981 by: the Science and Education Administration; July 1981- by: the Agricultural Research Service.
General Note: Description based on: Vol. 27, no. 7 (Jan. 1979).
General Note: Latest issue consulted: Vol. 46, no. 8 (Aug. 1998).
 Record Information
Bibliographic ID: UF00074949
Volume ID: VID00013
Source Institution: University of Florida
Holding Location: University of Florida
Rights Management: All rights reserved by the source institution and holding location.
Resource Identifier: ltuf - ABP6986
oclc - 01478561
alephbibnum - 000271150
lccn - agr53000137
issn - 0002-161X

Full Text


Fabulous Fruit-
Without Fumigation
Today's bountiful supply of
picture-perfect fruit-luscious cher-
ries, apples, mangoes, grapefruit,
avocados, papayas, carambola, and
bananas-overflows the produce
shelves of supermarkets often as a
direct result of Agricultural Research
Service efforts.
While nature makes possible a
wondrous bounty, the diseases and
insect pests that attack crops after
harvest are also part of nature. That's
why one facet of the ARS research
mission is to find ways to protect
susceptible fruits on their way to
For decades, chemical fumigation
has been the primary means of
protection. But many chemicals have
been taken off the market because of
health and environmental concerns.
So ARS scientists have been working
on alternatives-treatments like
irradiation, heat, cold, traps, and
biological controls in the field.
They're also looking at the host
status of particular fruits and at
insect-free zones, cultural practices,
and management systems that could
eliminate the need for fumigation. For
example, if it can be shown that a
fruit is not host to a specific pest, then
it won't need treatment for that pest.
Fly-free zones designate particular
areas uninhabited by fruit flies and
from which fruit can be shipped. One
such area is in northwest Mexico
along the border of Sonora, where
sterile flies have been released and the
area has been sprayed with chemicals
to rid it of the Mexican fruit fly.
USDA's Animal and Plant Health
Inspection Service (APHIS) has
certified this area free of the quaran-
tine pest, thereby lifting restrictions
on citrus movement.
Effective pest control is essential
not only for fruits slated for U.S.

export and import markets, but also
for internal quarantines between
growing areas in different parts of the
country. An example of an internal
quarantine is the recent discovery of
Mediterranean fruit flies in Florida,
which restricted movement of citrus
from a medfly-quarantined growing
area of Polk County.
We cannot import any product that
may be host to a pest that is not found
in the United States, unless it first
receives an approved treatment to
eliminate the risk of accidental
introduction. We must also have an
approved treatment for any crop that
we export to a country that doesn't
already have some of our pests.
Only two chemicals are currently
available for postharvest fumigation:
methyl bromide and phosphine. Phos-
phine can be used on stored products
like grains, almonds, and raisins, but it
is harmful, or phytotoxic, to fresh
commodities. This leaves methyl bro-
mide, which will be banned in the
United States, effective January 1,
2001-only three crop seasons away.
This impending ban has stepped up
the pace to find alternatives.
Take cherries, for instance. In 1996,
we exported 13,136 metric tons of
fresh cherries to Japan, worth $8
million. Japan required the U.S.
cherries to be treated with methyl
bromide to rid them of codling moth,
a pest that Japan doesn't have and
doesn't want.
ARS scientists are investigating
four alternative ways to protect cher-
ries: irradiation and three heat treat-
ment protocols, two of which are com-
bined with controlled atmospheres
(modified oxygen, humidity) during
storage. Industry has selected irradia-
tion and a heat with controlled atmo-
sphere treatment for commercial use.
Other ARS scientists are studying
the side-effects of these alternatives.
To be approved, a treatment must not
only kill codling moths, but it must do

so without affecting the quality of the
Apples, which also are plagued by
the codling moth, are currently being
shipped to Japan after methyl bromide
fumigation. We're now testing a heat
treatment followed by cold storage. It
has proved very effective for apples,
as well as for pears, which have never
before had a quarantine treatment
because of their perishability.
Hawaii is under a federal fruit fly
quarantine that prohibits shipment to
the U.S. mainland of fresh fruits and
vegetables that are fruit fly hosts. But
ARS is collaborating with the Univer-
sity of Hawaii to use irradiation and
heat treatments to make these fruits
eligible for mainland markets.
The Food and Drug Administration
approved use of irradiation on fruits
and vegetables in April 1986. Trial
shipments of Hawaii-grown exotic
fruits have been sent to a plant in
Illinois where they were irradiated and
then sold in Chicago, Indiana, and
Ohio. Consumer acceptance was
APHIS has approved the irradiation
treatment for papaya, carambola, and
lychee and has written appropriate
regulations. But these cover only fruit
flies, because scientists haven't yet
learned what irradiation doses would
be effective for other pests.
We're testing irradiation on blue-
berries to rid them of quarantine pests
like the blueberry maggot, apple
maggot, and plum curculio. Currently,
methyl bromide is the only approved
treatment for these pests.
ARS' ongoing quest for effective
replacements for fumigation should
ensure the steady movement of fresh,
quality agricultural produce into
international markets while keeping a
steady supply at home.

Kenneth W. Vick
National Program Leader for
Postharvest Entomology

Agricultural Research/January 1998

January 1998
Vol. 46, No. 1
ISSN 0002-161X

Agricultural Research is published monthly by
the Agricultural Research Service, U.S.
Department of Agriculture, Washington, DC
The Secretary of Agriculture has determined
that this periodical is necessary in the transac-
tion of public business required by law.
Dan Glickman, Secretary
U.S. Department of Agriculture
I. Miley Gonzalez, Under Secretary
Research, Education, and Economics
Floyd P. Horn, Administrator
Agricultural Research Service
Ruth Coy, Acting Director
Information Staff
Editor: Lloyd McLaughlin (301) 344-2514
Assoc. Editor: Linda McElreath (301)344-2536
Art Director: William Johnson (301) 344-2561
Acting Photo Ed.: Anita Daniels (301) 344-2956
Staff Photographer: Scott Bauer (301) 344-2957
Information in this magazine is public property
and may be reprinted without permission. Non-
copyrighted photos are available to mass media
in color transparencies. Order by photo number
and date of magazine issue.
Subscription requests should be placed with
New Orders, Superintendent of Documents,
P.O. Box 371954, Pittsburgh, PA 15250-7954.
See back cover for order form.
Complimentary 1-year subscriptions are
available to public libraries, schools, employees
of the U.S. Department of Agriculture, and the
news media. Send requests or comments to:
Editor, Agricultural Research Magazine, Room
408, 6303 Ivy Lane, Greenbelt, MD 20770. E-
This magazine may report research involving
pesticides. It does not contain recommendations
for their use, nor does it imply that uses dis-
cussed herein have been registered. All uses of
pesticides must be registered by appropriate
state and/or federal agencies before they can be
Reference to any commercial product or service
is made with the understanding that no discrimi-
nation is intended and no endorsement by the
U.S. Department of Agriculture is implied.
USDA prohibits discrimination in its programs
on the basis of race, color, national origin, sex,
religion, age, dihabilit. political beliefs, and
marital or familial status. (Not all prohibited
bases apply to all programs.) Persons with
disabilities who require alternative means for
communication of program information
(Braille, large print, audiotape, etc.) should
contact USDA's TARGET Center at (202) 720-
2600 (voice and TDD). To file a complaint,
write the Secretary of Agriculture, U.S.
Department of Agriculture. Washington, DC
20250, or call (800) 245-6340 (voice) or (202)
720-1127 (TDD). USDA is an equal opportu-
nity employer.

Agricultural Research

Heated Air Blasts Papaya Pests 4

Probing Plants' Water Needs I7

Florida Growers Like Lychees and Longans 8

An Ounce of Prevention Equals Pounds of Milk 10

Ubi7-New Tool for Potato Breeders 12

Fire Blight Control, Nature's Way 14

Biological Warfare Against Beet Armyworms 17

Range Reseeding Relies on Rodents 1 0

Keeping Pesticides on Target 20

Bigger, Better Berries Available Soon 21

Foxtail Millet for the Central Plains 22

Hypernodulating Gene Found in Soybeans 22

Science Update 23

Cover: Hawaiian papayas, Carica papaya. Photo by Scott Bauer. (K7932-1)

In the next issue!

0' A new trend in farming calls for restoring the land closest to streams and
rivers with plantings of native vegetation. It's a form of environmental
stewardship that protects waterways by capturing sediment and chemicals
from fields borne in runoff water.

(0 Retail sales of fresh-cut produce are expected to skyrocket to $19 billion
by 1999. "But maintaining quality of fresh-cut produce is a major concern of
the industry and a top Agricultural Research Service priority," says research-
er Kenneth C. Gross.

(0 Tightly compressed bales of freshly harvested hay destined for dairy
cows, beef cattle, or racehorses in Japan can now move swiftly through
agricultural inspections there, thanks to research by ARS scientists.

Agricultural Research/January 1998

r P4


SCOTT BAUER (K7888-16)

F resh, juicy papayas from
Hawaii can be kept free of
live fruit flies with a pack-
inghouse procedure from ARS and
the University of Hawaii.
Once used only on the islands of
Hawaii and Kauai, the hot-forced-air
technique today is on-line at packing-
houses on the islands of Oahu and
Molokai as well. It is credited with
easing entry to profitable mainland
U.S. markets and rescuing jobs that
might otherwise have been lost.
Hawaii's papaya growers pro-
duced about 42 million pounds of the
sweet-tasting fruit, worth about $17
million, in 1996. They specialize in
two varieties-the golden-fleshed
Kapoho Solo and Sunrise, a reddish-
orange type.
"Commercially grown papayas
from Hawaii are so carefully checked
that it's unlikely fly-damaged fruit
would make it to a mainland super-
market," says ARS entomologist
John W. Armstrong at Hilo, Hawaii.
"Our hot-forced-air process is simply
extra insurance."
Called a quarantine treatment, hot-
forced-air is one of three federally
approved techniques. The treatment
is similar to another option, called
vapor heat, but differs in that vapor
heat uses humidity differently.
Another approach, irradiation,
requires equipment not yet available
in Hawaii.
Hot-forced-air kills three different
kinds of crop-damaging fruit flies-
the Mediterranean fruit fly, oriental
fruit fly, and melon fly.
At the packinghouse, papayas are
placed in a chamber typically made
of stainless steel. Hot air, forced over
the surface of the fruit for at least 4

ARS entomologist John Armstrong (left)
and Jerry Vriesenga, president of Dole Food
Company Hawaii, discuss hot-forced-air
treatment for papayas that have been
partially tree-ripened.

hours, heats it to 1170F. Then the
fruit is cooled for about an hour.
Heat-treating papayas ensures that
pestiferous fruit flies can't hitchhike
to vulnerable farms, orchards, and
backyard gardens on the U.S. main-
Each of the three fly species,
already ensconced in Hawaii, "could
readily adapt to the warm, mild

The female Mediterranean fruit fly, shown
here on a coffee fruit, can deposit eggs 5
millimeters deep in papayas.

climates of California, Florida, or
other Sunbelt States and wreak
agricultural havoc," says Armstrong.
Medfly, for instance, "ranks as one of
the world's worst agricultural pests,
capable of attacking the fruit of more
than 300 different kinds of plants."
The 1995-96 outbreak of medfly in
southern California cost an estimated
$13 million.

Insect Offensive
The medfly, oriental fruit fly, and
melon fly each employ the same
extremely successful mode of attack,
says Armstrong.
"Females use their tubelike
ovipositors to pump tiny eggs into
the flesh of ripening fruits and
vegetables. Young maggots, or

Agricultural Research/January 1998

larvae, hatch from the eggs. They
use the fruit or veggie for food and
housing and turn it into a decaying,
unmarketable mess. The developing
larvae drop to the ground, form their
next lifestage-a pupa-while in the
soil, and later emerge as adult flies."
To garner regulatory approval,
Armstrong and colleagues tested the
hot-forced-air technique with a
research-size chamber at the ARS
Tropical Fruit, Vegetable, and
Ornamental Crop Research Labora-
tory in Hilo. Their experiments
began in 1987 and required more
than a quarter-million fresh papayas,
plus some 1.8 million laboratory-
reared fruit flies.
Armstrong did the work with
Steven A. Brown of ARS at Hilo;
James D. Hansen, now with ARS at
Wapato, Washington; Edward T.
Uyeda of USDA's Animal and Plant
Health Inspection Service and
Benjamin K.S. Hu, now retired from
that agency; Michael R. Williamson,
professor of biosystems engineering
with the University of Hawaii,
Manoa; and Paul M. Winkelman of
Quarantine Technologies Interna-
tional, Ltd., Honolulu.
ARS has registered the process
with the U.S. Patent and Trademark
Office. The University of Hawaii has
filed a patent application for the hot-
forced-air equipment.
Sunrise Packers on Kauai started
using hot-forced-air in 1993, the first
in Hawaii to do so. A new packing-
house for Kauai, expected to be up
and running in 1998, will boast two
new hot-forced-air units.
Hawaii Fruit Growers on Molokai
chose hot-forced-air in 1997 for their
first-ever papaya shipments to the
U.S. mainland. Those sales were so
successful that the co-op is now
building a second unit.
Dole Food Company Hawaii on
Oahu now has mainland U.S. mar-
kets for fresh papaya as well, thanks


to two hot-forced-air chambers that
the company installed in 1997. Dole
converted 600 acres of no-longer-
profitable sugarcane fields to papaya.
"We've rehired or newly hired
more than 80 people to work in
papaya production," says Dole Food
Company Hawaii president, Jerry D.
Vriesenga, "and we expect to hire
many more as the project grows."
Hot-forced-air also zaps medflies
and oriental fruit flies that might be
concealed in grapefruit and oranges,
according to experiments by Arm-
strong and co-workers. They tested a
total of about 6,500 Marsh White and
Marsh Red grapefruit, plus navel and
Valencia oranges, with funds from
the California citrus industry.
Their technique would serve as an
alternative process, should medfly or
oriental fruit fly-perhaps stowaways
in luggage or parcels of illegal
fruit-ever gain a foothold in main-
land citrus groves.-By Marcia
Wood, ARS.

Bill Pfeil (left), manager of Hawaii Papaya
Growers, and ARS entomologist John
Armstrong assess quality of papayas after
hot-forced-air treatment.

John W. Armstrong and Steven A.
Brown are at the USDA-ARS Tropi-
cal Fruit, Vegetable, and Ornamen-
tal Crop Research Laboratory, P.O.
Box 4459, Hilo, HI 96720; phone
(808) 959-9138, fax (808) 959-4323,
e-mail *

Michael Williamson (center), professor of biosystems engineering at the University of
Hawaii, Monoa, and Jerry Vriesenga (right), president of Dole Food Company Hawaii,
monitor papayas delivered by Dole employee Chris Awa for hot-forced-air treatment. Use
of lattice-bottom containers ensures uniform heating during treatment.

What Works in Hawaii Is Also
Good in Texas
A citrus pest that frequently shows
up in Texas-the Mexican fruit fly-
succumbs to hot-forced-air treat-
ments, according to 3 years of labora-
tory tests by ARS scientists.
Entomologist Robert L. Mangan
and plant physiologist Krista Shellie,
who are with ARS at Weslaco, Texas,
experimented with grapefruit, Valen-
cia oranges, and tangerines from
Texas' Rio Grande Valley. They
killed the insects by heating fruit until
their centers reached 113F and
holding that temperature for at least
110 minutes. The heat also protected
against spoilage organisms.
Federal officials are considering
the findings in proposing heat treat-
ments for Texas citrus.
Though gentler on citrus than
methyl bromide fumigation or cold
storage, heat treatments take time and
could cause costly delays in fruit-
handling operations. To sidestep this
problem, Mangan and Shellie com-
bined hot-forced-air with another
technology-controlled atmosphere.
They heated fruit with air containing
only 1 percent oxygen, compared to
the 21 percent in normal air.
"Low oxygen," explains Shellie,
"puts fruit in a slow-ripening, sleep-
ing state while it helps kill fruit flies."
Pairing the techniques, Mangan
and Shellie trimmed treatment time
for grapefruit from 5 hours to 3-1/2.
In 1996, growers in the Rio Grande
Valley produced about 332 million
pounds of fresh-market citrus with a
value of $57 million. The Weslaco
scientists are seeking corporate
partners to commercialize their citrus
treatments.-By Ben Hardin, ARS.
Robert L. Mangan and Krista
Shellie are in the USDA-ARS Sub-
tropical Agricultural Research
Center, 2301 S. International Blvd.,
Weslaco, TX 78596; phone (956) 565-
2647, fax (956) 565-6652, e-mail
mangan@pop. *

Agricultural Research/January 1998

Probing Plants' Water Needs
Automated time domain reflectrometry system measures soil moisture.

E very home gardener can
appreciate the desire to put
on only enough water-no
more, no less-to grow the best
tomatoes or the prettiest rose bush on
the block. For companies that grow
roses or tomatoes for a living, that
desire becomes a critical need.
Steven R. Evett and Robert J.
Lascano are collaborating to put
together a computerized irrigation
system that measures and calculates
how much water to apply every half
It's a simple concept, Lascano
says: "Replace just as much water as
the plants have used and you'll get
maximum yield with minimum
water." He is a soil physicist at Texas
A&M University in Lubbock who is
working with Evett, other scientists at
Texas A&M University, and Dy-
namax, Inc., of Houston, Texas.
Lascano designed the automated
system for applying irrigation water.
Evett is a soil physicist at the
USDA-ARS Conservation and
Production Research Laboratory in
Bushland, Texas. He designed the
automated time domain reflectometry
(TDR) system needed to determine
when to irrigate.
The measurement is done with
stainless steel probes placed in the
ground at varying depths, from a few
inches down to several feet.
A computer-controlled TDR
instrument sends an electronic pulse
through a buried cable to the probes.
The longer it takes for the pulse to
travel through the probe, the more
soil water. The probes work in most
irrigated agricultural soils, and one
TDR system can handle up to 241
probes, although the cable length is
limited to about 100 feet from the
USDA has signed a cooperative
research and development agreement
with Dynamax, which is now manu-
facturing the TDR system.

Evett says the probes are key
because they directly measure how
much water is left in the soil for
plants to use. He also designed the
software that controls the TDR system
and translates the probe signals into
water measurements.
The computer turns the water
pumps on and off at pre-determined
soil moisture levels, using software
written by Lascano.
Evett and Lascano have received
inquiries about the system from
managers of greenhouses, tree nurser-
ies, orchards, and vineyards.
The fully automated system may be
suited only for horticultural use, but
other farmers could use the probes
"They can install the probes
permanently anywhere they want,
with no limit on numbers of probes,"
says Evett. "They can drive around
their fields, stop at each probe and
connect the cable tester to each probe
for a reading. A laptop computer
translates the readings. This is fast
and easy. It's sometimes a practical
alternative to neutron probes that
require a license and special training
because of their radioactive content."
Lascano has grown cotton with an
automated drip irrigation system for 4
years. He says the tests have been
very successful so far and that auto-
mation could be used with other crops
and other irrigation systems. It could
also be used to study the effects of
pests and farm practices on crop water
use.-By Don Comis, ARS.
Steven R. Evett is at the USDA-ARS
Conservation and Production Re-
search Laboratory, P.O. Drawer 10,
Bushland, TX 79012; phone
(806)356-5775, fax (806)356-5750, e-
mail *

Software is available for
download on the USDA-
ARS Conservation and
Production Research
Laboratory web site at

TACQ.EXE time domain
reflectometry system
control software. Also look
for the system documenta-
tion in file
TACQ WPD.ZIP. You will
need the PKUNZIP.EXE
program to unzip the
documentation into Word-
Perfect files.

predicts crop water use.
Available, along with
source code and example
data files and documenta-
tion, in the self-extracting

Note: These programs are
supplied for information
purposes solely. No war-
ranty is intended, nor is any
service or support for these
programs provided.

Agricultural Research/January 1998

Research shows these fruits are not havens forfruitflies.

seemingly unending string
of hot, sunny days produces
an ideal environment for
growing tropical and subtropical fruit
at the southern tip of Florida.
Two unusual tropical fruits-
lychee and longan-are now impor-
tant commercial crops there. In 1996,
Florida growers harvested 1.37
million pounds of lychees, valued at
$2.75 million, and 875,000 pounds of
longans worth $1.75 million.
Last year, scientists at the ARS
Subtropical Horticulture Research
Station in Miami, Florida, ensured the
status of these fruits as viable com-
mercial crops by proving that neither
the longan nor the lychee hosts the
dreaded Caribbean fruit fly.
Entomologists Michael K.
Hennessey (now with the U.S. Envi-
ronmental Protection Agency) and
Walter P. Gould were aided by ento-
mologist Jennifer L. Sharp and plant
pathologist Raymond G. McGuire.
"Florida lychee and longan grow-
ers ship their fruit throughout the
United States," says Hennessey. "But
California had considered putting an
embargo on the fruit because it was
thought capable of harboring the
Caribbean fruit fly."
Working with the Lychee and
Longan Committee of the Tropical
Fruit Growers of South Florida, Inc.,
Hennessey and Gould developed a
protocol that proved neither fruit to
be infested by this pest. It has been
approved for use in California.
"This could very easily have been
a case of an internal quarantine of
two fruit crops that are easy to grow
here in south Florida," Gould ex-
plains. "But with the help of local
growers, we proved that these fruits
pose no agricultural risks."
The reddish-looking, exotic lychee,
a favorite fruit in Southeast Asia, is
about the size of a walnut and easily
peeled to expose sweet insides that
can be eaten fresh, canned, or dried.

Lychees, Litchi chinensis.

Also sweet tasting, longans are about
the size of grapes and grow in bunch-
es. A hard, tan-colored peel covers
white fruit that clings to a single seed.
For the research project, south
Florida growers supplied fruit from
six lychee groves (Mauritius and
Brewster varieties) on early-, mid-,
and late-season sampling dates. Of
the 450 fruits collected, a third were
held as a control, while the remainder
was exposed for a day to numerous
fertile female Caribbean fruit flies.
"We confirmed the fertility of the
flies by exposing them to guava, in
which the flies readily lay eggs,"
Gould explains. "We also made cuts
on one group of lychees, providing an
enticing place for egg laying."
But, to no avail. After exposure,
the lychees were held for 30 days to
allow time for any eggs laid in the
fruit to hatch and emerge as maggots.


Growers Like




Agricultural Research/January 1998

"After carefully inspecting each
lychee, we found no maggots or
larvae, indicating that no eggs had
been laid," says Gould. "During the
2-month fruiting season, we also
placed fly traps in each sample grove
and inspected them weekly. We found
no flies."
Hennessey and Gould repeated the
procedure with Kohala longans-and
again with top-quality longans and
lychees from the packinghouse.
"Again, we got the same results: no
flies," Gould reports.
Using guava as a control, Hennes-
sey tried one more test: covering
bunches of longans and lychees on
the trees with pollination bags hold-
ing five fertile Caribbean fruit flies.
After 24 hours, there was no
evidence that the flies had infested the
longans or lychees, but they had
attacked the guavas. After 30 days,
there was still no sign of attack on the
longans or lychees, but the guavas
were heavily infested.
As a backup, in case the fruit had
become infested, McGuire evaluated
fruit quality after irradiation and a
cold treatment, developed by ARS, of
longans and lychees. Both fruits held
up well under irradiation, maintaining
acceptable market quality. However,
chilling caused surface discoloration
of longans.
"There's an expanding market for
tropical fruits, in part because health-
conscious consumers are including
more fruits and vegetables in their
diets and want a variety to choose
from," says Hennessey. "Our aim is
to keep that supply plentiful."-By
Doris Stanley, ARS.
Walter P. Gould, Raymond G.
McGuire, and Jennifer L. Sharp are
at the USDA-ARS Subtropical Horti-
culture Research Laboratory, 13601
Old Cutler Rd., Miami, FL 33158;
phone (305) 238-9321, fax (305) 238-
9330, e-mail miarm@sun.ars- *




.1'.' '


~~, ~J;'

*y -...'
",?. :* *
** * i".

. e

This coming spring, Pennsylvania
dairy farmer Larry Lohr will treat his
cows just once with a wormer. That
should hold them until the end of the
grazing season, when he brings them
back in from pasture, says Agricultur-
al Research Service parasitologist
Lou Gasbarre. Then, Gasbarre recom-
mends one more treatment... just for
safe measure.
Even with the extra treatment, it
will be three fewer than Lohr gave his
cows in 1996 to battle the brown
stomach worm-Ostertagia ostertagi.
This roundworm makes its home
in the stomachs of dairy and beef cat-
tle in temperate regions worldwide.
Ostertagia accounts for 80 to 90 per-
cent of the worm problem in U.S.
beef and dairy cattle, costing the in-
dustry more than $2 billion annually.
The most common estimates put pro-
ducer costs at about $20 per animal
per year, says Gasbarre, who is with
ARS' Immunology and Disease Re-
sistance Laboratory in Beltsville,
Thanks to Gasbarre's recommen-
dation to take a prophylactic ap-
proach to the worm, Lohr's cows kept
a 3-pounds-per-day increase in milk
production last summer-that's 6
percent more milk-compared to the

same months in 1995 and 1996. And
they had "significantly higher body
weights," says Lohr.
Those increases in milk production
and body weight also had an environ-
mental benefit. Nitrogen that went
into the increased animal production
wasn't excreted in urine onto the pas-
ture, where a large portion of it would
have been susceptible to leaching into
the groundwater.
Lohr is among the first of a grow-
ing breed of dairy producers trying to
increase their net income by letting
cows feed themselves during the
growing season rather than cut, dry,
and store the feed and then serve it to
them later. Since he began pasturing
his cows 12 years ago, Lohr says he
has had "real good success. My annu-
al feed costs dropped about $150 per
cow." And it has increased efficiency
so much he has been able to increase
his herd from 45 to 100 cows.
When Lohr set up the intensive ro-
tational grazing system, no one ad-
vised him how to keep the brown
stomach worm from nibbling into his
profits. Although he routinely treated
his cows with a wormer during the
grazing season, milk production in-
creased after the treatments but then
dropped again, he says.

Lohr suspected that worms might
be causing this roller coaster effect.
He mentioned the problem at a meet-
ing at the Pennsylvania State Univer-
sity Center for Grazing Research and
Education, where he represents dairy
producers. Fellow center member,
ARS soil scientist Bill Stout, contact-
ed Gasbarre about the problem.
Together, the two scientists applied
for and received a grant from the Sus-
tainable Agriculture Research and Ed-
ucation Program, known as SARE,
for a 3-year study of Lohr's farm.
Funded by USDA to encourage low-
input production, SARE is adminis-
tered by the University of Vermont
for projects in the Northeast.
During the 1995 and 1996 grazing
seasons, Gasbarre observed Lohr's
operation. He also mixed worm-free
calves raised at the Beltsville center
in with Lohr's cows in order to mea-
sure infection rates. Lohr has 19
fenced, 1-1/2-acre paddocks on which
he rotates the cows daily.
With this scheme, the animals eat
the grass when it's most nutritious.
But it also fits into the worm's life cy-
cle perfectly for keeping infectious
larvae at high levels, says Gasbarre.
"The eggs take 10 to 14 days to be-
come infectious after they are passed

Agricultural Research/January 1998

in the feces. Normally, cows avoid
grazing near feces, where the para-
sites are heaviest. But in heavily
grazed paddocks, like this farm, cows
eat everything," he says. "There are
no tufts left."
With a 19-day rotation, the cows
were grazing each paddock shortly
after the eggs that had been deposited
in the previous rotation developed
into infectious larvae. The animals
kept becoming reinfected until the
worms built up to a critical level-
dropping milk production and animal
Gasbarre says some scientists and
veterinarians are not convinced that
worms reduce milk production, ani-
mal weight, or reproduction in fe-
males. They think cattle have enough
immunity to suppress infection.
But the evidence from Lohr's farm
belies that notion.
Gasbarre recommended that Lohr
treat his cows in the spring right after
they had made their first rotation
LOUIS GASBARRE (K7905-13) through all
19 paddocks.
That way,
any larvae
that survived
the winter
Sao8would be
h. picked up
and killed.
"The cows
act as big
cleaners," he
b'r don't pass
Cross-section of one es for 17p
brown stomach worm eggs for 17
larva looped inside a to 20 days
gastric gland. Magni- after they've
fled about 800x. been infect-
ed. By treat-
ing them after 19 days in contamina-
ted paddocks, it kills off the worms
before the eggs can pass out and

To estimate the number of brown stomach
worms in a pasture, researchers place a
worm-free calf on grass for a measured
length of time, then check for parasite eggs
in its feces.

And the theory worked, judging by
the worm-free calves that Gasbarre
mixed in with Lohr's herd throughout
the study.
Before treatment, the calves
passed the same number of eggs as in
the previous year. By the end of Au-
gust, only about 10 percent of the
calves had any eggs in their feces at
all. And these had only one or two,
says Gasbarre.
"Instead of a roller coaster effect,"
says Lohr, "we've evened out our
milk production."
In 1995, Lohr wormed his cows
five times. Last year, under the pro-
phylactic approach, he wormed them
three times. This year, it will drop to
two treatments-one in the spring, af-
ter the first 19-day rotation, and an-
other at the end of the grazing season.
Lohr will have to continue treating
his cows each spring to retard larvae
build-up, Gasbarre says. But pasture
levels are so low now that the second
treatment is just for insurance. "It's
more expensive to clean up the prob-
lem than to prevent it.
"We don't want the animals to
never see a parasite," he adds. "They
need to build up some exposure to
stimulate their immune systems. But
you want to keep the exposure below
a level where the parasites over-
whelm the immune system."
Gasbarre emphasizes the impor-
tance of considering health issues
when setting up animal management

"Lohr would not have gotten to this
point if he had been advised to man-
age his pastures for parasites-using
prophylaxis," he says.
He recommends that producers treat
their animals once, then watch the
weather and give follow-up treatments
"The larvae thrive in cool, wet
weather. A prolonged dry spell will
slow them down, especially combined
with hot weather," says Gasbarre.
As part of the funding for this
study, the Northeast SARE review
committee wanted to know how many
other producers in the region felt they
had a worm problem and what man-
agement practices might be contribu-
ting to it. Stout and Gasbarre devel-
oped a questionnaire that was sent to
2,000 livestock producers-from
Maine to Maryland.
Nearly 800 responded, and the re-
searchers are still analyzing the data.
Preliminary indications are that 40
percent of the respondents didn't
know if worms were a problem on
their farm. One-third reported worms
to be a moderate problem, while a lit-
tle more than one-quarter didn't think
they had a worm problem. Lohr is now
among those without a problem.
"It proves the system will work if
done properly," he says. "If farmers
have a problem, they should go after an
answer."-By Judy McBride, ARS.
Louis C. Gasbarre is at the USDA-
ARS Immunology and Disease Resis-
tance Laboratory, Bldg. 1002, 10300
Baltimore Ave., Beltsville, MD 20705-
2350; phone (301) 504-8509, fax
(301) 504-5306, e-mail
William L. Stout is at the USDA-
ARS Pasture Systems and Watershed
Management Research Laboratory,
Curtin Rd., University Park, PA
16802-3702; phone (814) 863-0947,
fax (814) 863-0935, e-mail *

Agricultural Research/January 1998

Ubi7-New Tool for Potato Breeders

tomorrow's potatoes might
easily fend off rot-causing
microbes, thanks in part to a
friendly gene known as ubiquitin7.
ARS researchers snipped part of the
gene, hooked it onto a soft-rot-
fighting gene, and inserted this new
combination into experimental
In preliminary laboratory and
greenhouse tests, the tubers resisted
attack by the microorganism that
causes soft rot, according to William
R. Belknap of the Agricultural Re-
search Service's Western Regional
Research Center in Albany,
The piece of the ubiquitin7, or
ubi7, gene that scientists prize is
called a promoter. Its job: to turn a
gene on. To a genetic engineer, a
strong promoter is an invaluable tool.
For more than three decades,
scientists have known that promoters
borrowed from one gene can be fitted
onto another to boost the second
gene's effectiveness. Ideally, the
borrowed promoter also dictates when
and where within the plant the gene
should turn on.

Plant physiologist William Belknap uses a
DNA synthesizer to make rot-fighting genes
for experimental potatoes.

Ubi7 captured the attention of
Belknap's team because wounding
turned on that gene in tubers analyzed
in their laboratory.
"When wounding occurs," says
Joan E. Garbarino, "rot may follow.
We reasoned that hooking rot-fighting
genes to the ubi7 promoter would
make the anti-rot gene more effective
when tubers were damaged-the time
they need protection the most."
That is what happened in Garbar-
ino's laboratory tests with quarter-
inch-thick slices of greenhouse-grown
potatoes. The tubers had the ubi7
promoter, hitched to the anti-rot
genes, working inside.
To simulate the injury that might
occur as potatoes make their way
from field to table, Garbarino stabbed
the slices with a toothpick, then
exposed them to the rot-causing
organism, Erwinia carotovora. After
5 days, tubers with the ubi7-driven
anti-rot genes had 85 to 96 percent
less decay than those without this
gene-promoter combination. Slices
from conventional potatoes turned
watery with decay.
Garbarino works in Belknap's
laboratory under a cooperative
research and development agreement
initiated in 1994 between Demeter
BioTechnologies, Ltd., of Durham,
North Carolina, and ARS. The
company developed the rot-resistance
genes used in the experiments. ARS
and Demeter are seeking a patent for
the ubi7 promoter.

Not Just a Problem in Potatoes
The E. carotovora bacterium that
causes soft rot gets its name from
carrots, the crop in which it was first
isolated and named. A soil-dwelling
microbe, it invades potatoes and other
crops either in the field or in storage.
The rot causes afflicted tissue to
become soft and watery and then turn
slimy and foul-smelling.

E. carotovora also ruins other
vegetables and fruits including
cucumbers, onions, tomatoes, lettuce,
and some ornamental plants like iris.
"We refer to Erwinia carotovora as
the 'flesh-eating bacteria' of the plant
world,'" says Richard D. Ekstrom,
Demeter's president. Though ARS
tests have been limited to potatoes,
the scientists anticipate that these
other crops might also benefit from
new protection offered by Erwinia-
resistance genes linked to the ubi7
gene's adept promoter.
Potatoes need antimicrobial
protection because damage from
machinery and routine jostling and
tumbling during harvest and handling
"is unavoidable, despite the concerted
effort by growers and shippers to
handle tubers gently," says Belknap.
In their laboratory experiments,
Belknap and Garbarino worked with
David R. Rockhold of the Albany
center and former Albany colleagues
Timothy M. Rickey and Teruko

Joan Garbarino, a research scientist with
Demeter BioTechnologies, Ltd., examines
greenhouse potato plants containing
Demeter's microbe-resistance genes.

Agricultural Research/January 1998


For their lab tests, ARS plant physiologist William Belknap and Demeter's Joan Garbarino
will harvest tubers from these genetically engineered potato plants.

Belknap provided dozens of the
genetically engineered tubers to ARS
scientists at Aberdeen, Idaho, for the
1997 growing season. They're com-
pleting the first-ever outdoor tests of
the anti-rot genes hitched to the ubi7
ARS plant pathologist Dennis L.
Corsini and geneticist Joseph J. Pavek
lead those experiments. They're
scrutinizing the high-tech tubers not
only for soft rot resistance, but also
for size and other traits important to
growers and consumers.
Previously at Albany, the team had
discovered another ubiquitin gene,
which they named ubi3. In early tests,
it seemed the ubi3 promoter should
turn on genes in wound tissue when
injury occurred. "But we couldn't get
that to happen," Garbarino says. "We
saw ubi3 go to work in wounded and
nonwounded tissue alike, even in
leaves, for example."
However, an increasing need-
worldwide-for new promoters has

meant that plant genetic engineering
researchers have been anxious to try
out ubi3. So far, Belknap has shipped
the promoter to more than three dozen
labs in the United States and abroad.
"We make ubi3 available free of
charge to any molecular biology lab
that needs it," says Belknap. "It seems
to be a good all-purpose promoter for
switching a gene on and leaving it on."
To home in on the ubi3 and ubi7
genes, Belknap used a ubiquitin-
seeking molecular probe from Peter
H. Quail of the University of Cali-
fornia at Berkeley and ARS Plant
Gene Expression Center at Albany.
The probe derives from the ubiquitinl
gene that was discovered by Quail,
former Albany colleague Alan H.
Christensen, and others.
Potatoes are America's most
popular vegetable. U.S. potato grow-
ers produced about 25 million tons of
the tubers in 1996, worth about $2
billion. Though some are raised for
fresh-market sale, most are processed

into fries, chips, dehydrated flakes, or
other top-selling products.-By
Marcia Wood, ARS.
William R. Belknap is in the
USDA-ARS Crop Improvement and
Utilization Research Unit, Western
Regional Research Center, 800
Buchanan St., Albany, CA 94710;
phone (510) 559-6072, fax (510) 559-
5775, e-mail
Dennis L. Corsini and Joseph J.
Pavek are in the USDA-ARS Small
Grains and Potato Germplasm
Research Unit, 1691 South 2700
West, Aberdeen, ID 83210; phone
(208) 397-4162, fax (208) 397-4165,
Peter H. Quail is with the USDA-
ARS and University of California at
Berkeley Plant Gene Expression
Center, 800 Buchanan St., Albany, CA
94710; phone (510) 559-5900, fax
(510) 559-5678, e-mail *

KEN HACKMAN (K7812-18)

. 1 .
Tests of potato genetic material, or DNA,
loaded onto an agarose gel, reveal the
presence of an experimental gene.

Agricultural Research/January 1998

Plant pathologists Virginia Stockwell (ARS) and Oregon State University's Kenneth Johnson inspect Bosc pear trees
and prune out fire-blight-affected branches.

A pples and pears are big
business for both large and
small fruit growers in the
Pacific Northwest. Washington,
Oregon, and California produce more
than 6 million tons of the two fruits
annually, worth more than $2 billion.
Research by ARS and university
scientists is helping the growers
manage one of the industry's major
disease challenges, fire blight. In
addition to the standard chemical
controls, growers are beginning to
have access to another tool: biologi-
cal control.
The bacterium Erwinia amylovora
causes the blight. Wind, rain, and
insects carry the bacteria to fruit
blossoms. Warm, wet weather helps
the bacteria reproduce. Once a large

population builds up, the bacteria can
infect the blossom and spread inter-
nally through the stem. Fire blight
isn't a problem every year, but when
it does flare up, growers can spend
thousands of dollars removing infect-
ed tree limbs.
In the 1950's, the antibiotic strepto-
mycin became the treatment of
choice. Copper and other chemicals
joined the arsenal later.
But the favored streptomycin began
losing its effectiveness in the 1970's
because E. amylovora was showing
resistance-at least in California.
In 1988, ARS plant pathologists
Joyce E. Loper and Rodney G.
Roberts spearheaded an effort that
showed streptomycin resistance was
taking hold in Washington. Since

then, ARS plant pathologist Virginia
0. Stockwell has found streptomycin
resistance in Oregon.
"Unfortunately, streptomycin
sprays for fire blight control are less
reliable than in the past," Stockwell
says. She and Loper work at the
Horticultural Crops Research Labora-
tory in Corvallis, Oregon. Roberts is
at the Tree Fruit Research Laboratory
in Wenatchee, Washington.
To help growers manage the
streptomycin resistance, the ARS
scientists intensified their work-and
helped with university research
already under way-on biological
control options.
The first commercial biological
control product went on the market in
1995 after years of testing. Blight

Agricultural Research/January 1998

Ban, produced by Plant Health
Technologies of Boise, Idaho, uses a
beneficial bacterium, Pseudomonas
fluorescens Pf-A506. This strain of
Pseudomonas competes with the fire
blight organism for nutrients on
blossoms, keeping the numbers of
Erwinia low enough to avoid severe
infection. The key is to give the
biocontrol organisms a head start so
they can build up a large population
before the pathogen arrives.
Steven E. Lindow, plant patholo-
gist at the University of California-
Berkeley, discovered Pf-A506 in
1979 as beneficial for reducing fire
blight and frost damage. To confirm
its effectiveness, ARS scientists
contributed 5 years of testing to
Lindow's 16 years. Working with
Oregon State University plant
pathologist Kenneth Johnson, Stock-
well and Loper also found that Pf-
A506 maintains optimum effective-
ness if freeze-dried.
Another important finding: The
biocontrol can be used safely with
antibiotics-but not with copper,
which is also used for fire blight
control. Now they're testing Pf-A506
in combination with other biocontrol
organisms, such as E. herbicola C9-
1. Although this bacterium is related
to the pathogen that causes fire
blight, it is a different species and
does not hurt the fruit trees. In fact,
C9-1 produces antibiotics that inhibit
the growth of E. amylovora. Plant
Health Technologies hopes to use
C9-1, once registration with the U.S.
Environmental Protection Agency is

More Biocontrols on the Way
A new technique developed by
ARS plant pathologist Larry Pusey in
Wenatchee is speeding up the search
for effective biocontrols. The tech-
nique allows efficient, year-round
screening for naturally occurring

organisms with the potential to
suppress E. amylovora.
Pusey's method uses crab apple
nursery stock. These trees are cheap
and readily available because they
are used by growers to help pollinate
apple orchards.
Pusey gets the small trees from
nurseries in December or January. He

The first commercial
biological control
product went on the
market in 1995 after
years of testing. It
uses a beneficial
bacterium strain that
competes with the fire
blight organism for

uses some and holds others dormant
until needed. By stripping leaves off
trees that have already provided
blossoms and adding a growth
hormone, he can induce individual
trees to bloom twice in 12 months.
Currently, he gets new stock every
year, but he thinks he can manipulate
the trees to provide blooms twice a
year for 2 or 3 years before new ones
are needed.
Pusey developed a laboratory
assay that uses live blossoms plucked
from greenhouse trees to test for
effectiveness of an organism in
controlling fire blight. He is now in a
position to pre-screen thousands of
new organisms and conduct in-depth
studies with those that are especially
promising. Previously, researchers
had to assess the value of potential
biocontrols by growing them on

sliced pear fruit, which is very
different from the flower tissue the
slices are meant to represent.
"Our lab results closely mirror
what happens in actual field studies,
or what would happen assuming that
field studies could be done. Fire
blight is not a problem every year. If
the right weather conditions aren't
present, we can't successfully field-
test new organisms," says Pusey.
Pusey has one natural bacterial
strain that seems very promising. He
has applied for a patent and private
industry has shown interest in further

Consistently Inconsistent
Because biological controls are
living organisms, they don't always
perform consistently over a wide
range of conditions. Loper and
Stockwell in Corvallis are trying to
resolve that problem at a genetic
"Variability is a huge obstacle to
using biocontrol in agriculture,"
Loper says. "The goal of our work is
to identify sources of variability so
that we can use biocontrol organisms
more effectively."
When sprayed on trees, Pf-A506
often establishes well on pear or ap-
ple blossoms. But it sometimes dies
off rapidly and does not persist long
enough to suppress the fire blight
pathogen. On the plant surface, bac-
teria face drying out desiccationn)
and temperature changes, Loper says.
Her goal is to manipulate beneficial
bacteria genetically to help them
thrive under adverse conditions.
In Pseudomonasfluorescens Pf-5,
a strain related to the active bacterial
agent in Blight Ban, Loper identified
a gene called rpoS that governs how
bacteria respond to environmental
stresses like desiccation. Stockwell
and Loper are now doing field tests
to see if rpoS influences the capacity

Agricultural Research/January 1998

of Pf-A506 to survive on blossoms or
to suppress fire blight.
ARS' commitment to fire blight
control doesn't stop at the orchard
fence. Plant pathologist Roberts has
worked for the last 11 years on inter-
national plant quarantine issues relat-
ed to fire blight. The West Coast fruit
industry depends heavily on exports
to maintain profitability and good do-
mestic prices, but the presence of fire
blight in the United States has limited
development of new markets in Asia,
Europe, and Australia.
Roberts' work showed that com-
mercially produced apples from
Washington do not pose a significant
risk of carrying the fire blight patho-
gen to countries where fire blight
does not occur. Roberts also led a
team that confirmed the effectiveness
of a postharvest chlorine treatment
now used for all apples exported to
Similar research with pears done
collaboratively by Roberts and Pusey
kept open the Brazilian export
market-currently valued at $35
million annually-and might allow
future exports to Chile, should U.S.
growers attempt to develop a pear
market there.-By Kathryn Barry
Stelljes and Dennis Senft (retired),
Joyce E. Loper and Virginia 0.
Stockwell are at the USDA-ARS
Horticultural Crops Research Labo-
ratory, 3420 N.W. Orchard Ave.,
Corvallis, OR 97330; phone (541)
750-8760, fax (541) 750-8764, e-mail
Larry Pusey and Rodney G.
Roberts are at the USDA-ARS Tree
Fruit Research Laboratory, 1104
North Western Ave., Wenatchee, WA
98801; phone (509) 664-2280, fax
(509) 664-2287, e-mail
pusey @ *

Plant pathologists Virginia Stockwell (left) and Joyce Loper examine genetically engineered
bacteria on a colony counter.

Agricultural Research/January 1998

Biological Warfare Against

Beet Armyworms

B beneficial insects are often
victims of "friendly fire"
when farmers spray insecti-
cides to battle crop-damaging beet
But now, a more selective ap-
proach is in the works at two Agri-
cultural Research Service labs in
Mississippi. Scientists there are re-
cruiting two of the armyworm's most
formidable natural enemies, and it
looks to be a grisly affair.
One recruit is a natural insect
pathogen known as a Spodoptera
exigua nuclear polyhedrosis virus
(SeNPV). It liquefies the bodies of
armyworms it infects but poses no
danger to humans, animals, or
helpful predators like big-eyed bugs,
which eat other crop pests.
The SeNPV organism is also
harmless to the scientists' other re-
cruit: Cotesia marginventris, a wasp
that parasitizes armyworms.
Exploiting the virus as a biological
control agent is the goal of entomolo-
gists Randy Bell and Doug Streett,
who are at ARS' Southern Insect
Management Research Laboratory in
Stoneville, Mississippi. In nature, the
SeNPV virus inhabits the soil. But
the researchers showed it can be for-
mulated and sprayed onto cotton
plants as a so-called biopesticide.
When they tested the approach in
field studies, about 60 percent of
armyworms died within 4 days of
chewing on the virus-treated plants.
Once ingested, the virus replicates
millions of times inside the worm's
body, turning the pest's tissues into a
dark, slushy mess.
"These particular pathogens are
very host-specific and kill rather
quickly compared to other NPV,"
says Bell, who is retired but serves as
a consultant at the Stoneville lab.
This summer, another round of
field studies on cotton is planned in
collaboration with Dupont Chemical
Company scientists. Of particular

interest will be use of a feeding
stimulant to ensure worms get an
unhealthy dose of the lethal virus.
Meanwhile, about 130 miles east,
entomologist P. Glynn Tillman is
perfecting techniques for rearing the
Cotesia wasps and other helpful para-
sites at ARS' Biological Control and
Mass Rearing Research Unit located
near Starkville, Mississippi.
Tillman envisions unleashing Co-
tesia to attack armyworms that
plague greenhouse-grown crops. This
would help growers save on insecti-
cides and costly, uncomfortable pro-
tective gear that must be worn to ap-
ply the chemicals indoors.

A biological control agent, nuclear
polyhedrosis virus, killed the beet
armyworm at top.


Like the SeNPV virus, the wasp
also depends on the armyworm to
further its own reproduction and sur-
vival. After mating, a female Cotesia
can lay eggs in 30 armyworms a day,
and once parasitized, the caterpillars
are as good as dead. Within days,
they become a nutritious meal for
hungry wasp larvae that hatch from
the eggs. After emerging from their
hosts, the larvae spin a cocoon, pu-
pate, and become adult wasps.
Armyworms sometimes evade
chemical sprays by hiding beneath
plants' leaves. But they may not be so
lucky when a parasite like Cotesia is
released. "That's because the wasps
will actually go to where the pests
are," says Tillman.-By Jan
Suszkiw, ARS.
P. Glynn Tillman is in the USDA-
ARS Biological Control and Mass
Rearing Research Unit, P.O. Box
5357, Mississippi State, MS 39762;
phone (601) 323-2230, fax (601) 323-
0478, e-mail
Randy Bell and Doug Streett are at
the USDA-ARS Southern Insect Man-
agement Research Laboratory, P.O.
Box 346, Stoneville, MS 38776;
phone (601) 686-5231, fax (601) 686-
5421, e-mail *

Entomologists Randy Bell and Patricia lillman searcn a cotton nela ror evidence or
infestation and damage by beet armyworms.

Agricultural Research/January 1998

Range Reseeding Relies on Rodents

'.,~. *81

Kangaroo rats and their relatives are
responsible for more than 90 percent of the
germination and establishment of Indian
ricegrass seedlings.


.. . .* _

Animal ecologist William Longland
inspects Indian ricegrass growing in
Nevada's Great Basin during the Hot
Springs Mountain granivore study. The pen
in the background was designed to allow
access to rodents but exclude other seed-
eating animals.


A key to establishing range-
land plants may be the
kangaroo rats and chip-
munks that eat the seeds.
Land managers often reseed areas
disturbed by fire or mining to hold
the soil in place, provide food for
livestock and wildlife, and ward off
invasive weeds. When possible, they
try to use plants native to the area
they are planting. But their success
can depend not only on soil type and
precipitation, but on the local animals
as well.
"A revegetation plan is likely to
fail if rodent populations aren't
considered," says Agricultural
Research Service animal ecologist
William S. Longland.
That's because Longland and
others have found that certain native
plants depend on rodents for germi-
nation in the wild. Longland works at
the ARS Ecology of Temperate Des-
ert Rangelands Laboratory in Reno,
Nevada. He's studying local wildlife
to develop the best strategies for es-
tablishing native plants on the range.
Two of the most economically
important plants in Nevada's Great
Basin are Indian ricegrass and the
shrub called antelope bitterbrush. The
basin extends from the Sierra Nevada
and Oregon-Idaho border east to the
Wasatch Range in Utah and south to
the Mojave Desert.
"In the winter, many Western
ranchers rely on rangeland grasses to
feed their cattle, and mule deer
depend on shrubs like antelope
bitterbrush," says ARS rangeland
scientist James A. Young, who leads
the Reno laboratory.
Frosty Tipton is one of those
ranchers. He feeds about 1,100 cows
on 250,000 acres of owned and
leased land.
"If we didn't have access to
rangeland, we'd have to put up hay
for the winter," he says. "But we
don't own enough land to produce up

Agricultural Research/January 1998


Research technician Charlie Clements (left)
and animal ecologist William Longland
inspect bitterbrush, which is a major
source of browse for mule deer.

to 1 ton of hay needed for each cow
per month-I don't know what our
ranch would do without the winter
range," he says.

Planting's a Costly Affair
Replanting with native seeds can
get expensive. Indian ricegrass seeds
cost between $5 and $30 per pound,
depending on whether the variety is
commercially grown or locally
harvested from the wild. Antelope
bitterbrush seed costs up to $18 per
pound. For comparison, a non-native
grass, crested wheatgrass, sells for
only $1.70 per pound.
That's where understanding the
seed-eating granivores comes in.
Longland just finished a 4-year
study of Great Basin granivores,
including birds, ants, and rodents. He
found that birds have little influence,
because other granivores generally
beat them to the seeds. Ants eat the
seeds or take them too far below
ground to germinate. But the rodents
can be essential.

Labor That's Wild and Free
In field experiments, Longland
discovered that kangaroo rats and their
relatives were responsible for more
than 90 percent of the germination and
establishment of Indian ricCgra

"These rodents gather hundreds of
seeds in their cheek pouches and then
bury them in shallow hiding places,
or caches," Longland says. "Later,
they'll return and eat the seeds, but
some get missed. The caches put the
seeds in an ideal location for germi-
nation and protect them from other
rodents and ants," he says. Scientists
also believe that chemicals or
friendly microbes in the cheek
pouches break the seeds'
dormancy, another needed
step before seedlings can
Steven B. Vander Wall,
an animal ecologist with
the University of Nevada at
Reno, found that antelope
bitterbrush has an ever
greater association with
chipmunks and squirrels.
In contrast to these
beneficial effects on natural
seedlings, however, rodents
can hamper artificial
revegetation efforts by
eating the planted seeds.
"With some traditional
reseeding operations,
rodents will go up the
closely spaced rows of
shallow-planted seeds just
like they're in a buffet
line," Longland says. The long
Seeds ca
A Battle of Wits in vario
new Ind
Young, Longland, and
colleagues have come up with two
strategies for outwitting the crafty
The first is to plant fewer seeds-
but at a greater depth and more
widely spaced than traditional
seeding operations. "Normally, the
shallow-planted seeds would have a
better chance to germinate," says
Young. "But planting deeper seems
to deter the rodents, so a greater
percentage of the total planted stays
in place long enough to sprout."

Another plus: An ultra-low
seeding rate reduces the cost of native
plant restoration up to 25-fold.
Since this technique was devel-
oped in 1994, it has become the
standard for seeding Indian ricegrass
in the Great Basin. The tricky part is
getting the seed drills to plant the
seeds sparsely. Adding an inert
material like vermiculite or rice hulls
in the drill box allows the equipment

g-tail pocket mouse, a close relative of kangaroo rats,
cheek pouches characteristic of this family of rodent,
rried in the pouches as the mouse forages are then bi
us locations, aiding the distribution and establishment
ian ricegrass stands.

to work normally but spreads out
placement of the seeds.
The second approach takes advan-
tage of the animals' natural tendency
to cache seeds.
"Kangaroo rats and other caching
rodents don't eat most of the seeds
they collect until later," Longland
says. The new method, still under
development, would allow the
rodents to cache the newly planted,
desired seeds. Then, land managers

Agricultural Research/January 1998

would provide a cheaper commercial
seed that the rodents prefer, such as
millet. This cheaper seed would be a
decoy, or sacrifice-recovered first
from the cache, since the rodents like
it better, leaving more of the native
seeds in the ground to germinate.
"Our tests to date indicate this
could work," Longland says. Rodents
did like the millet better than the
native plant, four-wing saltbush. But
so far, they haven't found
anything the animals like
better than Indian ricegrass.
The most immediate
practical application for
Longland's work may be as
a predictive tool.
"If we know which
rodents live in an area that
has been disturbed, we
should be able to estimate
how the area will recover
without artificial reseed-
ing," he says.
For example, in 1985, a
fire burned 6,800 acres near
Flanigan, Nevada, by the
California border. Land
managers planted seeds to
stabilize the area. The next
year, lush growth of Indian
ricegrass appeared-but it
was not from the seeds in
the revegetation mixture.
buried "If we'd had a good
t of understanding of the rodent-
Indian ricegrass ecology at
that time, we might have
been able to save the time and money
that went into the reseeding," Long-
land says. "In some cases, disturbed
areas will recover naturally."-By
Kathryn Barry Stelljes, ARS.
William S. Longland is at the
USDA-ARS Ecology of Temperate
Desert Rangelands Laboratory, 920
Valley Rd., Reno, NV 89512; phone
(702) 784-6057, fax (702) 784-1712,
e-mail *


Keeping Pesticides on Target

W hen scien-
tists in the
ARS Appli-
cation Technology Research Unit at
Wooster, Ohio, focus their technolo-
gy, it's delicate crystalline shapes of
pesticides that come into view.
A combination of high magnifica-
tion, x-ray technology, and computer
imaging software makes it possible
for the scientists to see individual
crystals of pesticides dried on the
surface of a plant leaf.
Charles Krause, an Agricultural
Research Service plant
pathologist, says the CRAIG TAPAN/CH_
combined technolo-
gies-called electron
beam analysis, or
EBA-offer research-
ers a way to pinpoint
precisely where
pesticide products are
going on the plant.
Information from the
closeup pictures also
allows scientists to
determine the chemical
makeup of a particular
Within the 100,000-
times magnification of
a scanning electron
microscope, some
individual fungicide
crystals look much like
snowflakes resting on
the leaf surface. Each Scanning ele
chemical formulation Magnified aL
has unique characteris-
tics that make it
possible for scientists
to identify the com-
pound used. For example, the fungi-
cide chlorothalonil has a distinct
crystalline shape. Another type of
fungicide, copper hydroxide, appears
as small granules. Such knowledge
helps scientists determine what
specific chemicals are reaching
intended targets.

To capture a picture of the object
being viewed, scientists use a type of
x-ray analysis and digital imaging
software built into the EBA equip-
ment. This allows them to get clear,
sharp photographs of individual
chemicals and store them on a
computer disk just like any other
computer file.
"Digital imaging is safer, more
efficient, and less expensive than

citron mlcrograpn oI a
pout 4000x.

conventional photographic film
processing," says Krause. "The
process uses no toxic chemicals that
present disposal problems. And we
can use this digital image in a variety
of ways, either to analyze or archive
samples or to send them as electronic
mail over the Internet to other

The develop-
ment and use of
EBA has
evolved along with computers,
Krause says. It improves scientists'
ability to evaluate pesticides at the
point of delivery. This is important
because of increasing concern over
their impact on the environment.
Traditional residue analysis
targets one or two different aspects
of the chemical. Electron beam
analysis can directly detect the
whole spectrum of chemical ele-
ments present in
the residue.
"Our goal is
to ensure that all
of the control
agent reaches
the target
surface-not the
soil, the worker,
or the environ-
.ment. We want
all of the control
agent to go
where it is
needed. This is a
key step in
integrated pest
strategies," says
Dawn Lyons-
Johnson, ARS.
Charles R.
Krause is in the
Research Unit,
Ohio Agricultural Research and
Development Center, 1680 Madison
Ave., Wooster, OH, 44691; phone
(330) 263-3672, fax (330) 263-3841,
e-mail *

Agricultural Research/January 1998

F ruit salads, ice cream, and
pastries may soon be bursting with
new berry varieties from the Agricul-
tural Research Service.
Five just-released cultivars of
blackberries, blueberries, and straw-
berries promise to delight not only
consumers, but growers ranging from
home gardeners to commercial
"In general, these berries ripen
before or after the typical growing
season, making fresh fruit available
longer each summer," says geneticist
Chad E. Finn. Finn developed and
released the berries with cooperation
from other ARS scientists and
Oregon State University. He works at
the ARS Horticultural Crops Re-
search Laboratory in Corvallis.
Another advantage, says Finn, is
that many of the new cultivars
produce much larger fruit than their
existing commercial counterparts.
The two new blackberries are
prime examples. Black Butte berries
are among the world's largest.
Averaging 2 inches long and 1 inch
in diameter, they are almost twice the

size of most fresh blackberries.
Siskiyou is also large and especially
sweet. This berry starts ripening a
couple of weeks ahead of the main
berry season, to hit the fresh market
early; later fruit from the same vines
can go into yogurt, ice cream, and
bakery products.
"Both of these large blackberries
are quite attractive to pick-your-own
operators and large commercial
growers," says Charlie Boyd, who
propagates the berry plants at Cedar
Valley SCOTT BAUER (K7773-2)
Nursery in
"Siskiyou has
established a
niche market
and com-
mands a
Chandler, a
also bears
very large
fruit. This late
berry comes
in after the
industry l
standard, Black Butte blackberries
Bluecrop. blueberries were released
While most Agricultural Research Se
While most University.
ripen over a 3-
week period, Chandler provides ripe
fruit for 4 to 5 weeks.
Chandler was initially selected and
developed by Arlen Draper at the
ARS Fruit Laboratory in Beltsville,
Maryland. Mark K. Ehlenfeldt, a
geneticist at the ARS Blueberry/
Cranberry Research Laboratory in
Chatsworth, New Jersey, completed
its development and cooperative
release with ARS in Oregon.

I coi

Two new strawberries, Firecracker
and Independence, also produce
berries longer. "These strawberries
begin ripening around the 4th of July
and extend the season up to 3 weeks,"
says Finn. A less obvious benefit to
the extended season, he says, is that
growers can keep their field workers
employed longer.
An order to your favorite berry
nursery this winter should ensure the
new varieties arrive for spring plant-
ing. Growth and ripening will vary, of
course, de-
Spending on
location and
you grow these
berries your-
self or just
enjoy them
from the
(where they
should show
up in a few
years), you'll
be doing your
body a favor.
Berries are
high in fiber
and vitamin C
but low in
SChandler recent research
operatively by the by ARS and
e and Oregon State others indi-
cates that
and blueberries contain high levels of
antioxidants and other chemicals that
help a person stay healthy.-By
Kathryn Barry Stelljes, ARS.
Chad E. Finn is at the USDA-ARS
Horticultural Crops Research Labo-
ratory, 3420 NW Orchard Ave.,
Corvallis, OR 97330; phone (541)
750-8760 or 750-8759, fax (541) 750-
8764, e-mail +

Agricultural Research/January 1998

Foxtail Millet for the
Central Plains

"Farmers have learned at our field days that the time-
honored practice of growing winter wheat, then letting
land remain fallow, or cropless, is a waste of precious
moisture and cuts into their profit margins," says Randy
L. Anderson. "Now, they're discovering that there's
enough moisture on the central Great Plains for a crop
rotation that includes foxtail millet, along with wheat.
"Best of all, growers net more profit with new crop
rotations," he says.
Foxtail millet joins other crops like proso millet and
sunflowers in crop rotations that are slowly replacing the
older routine of wheat one year, then fallow the next.
The area gets about 16-1/2 inches of precipitation
annually, or 33 inches every 2 years. That's more water
than a single wheat crop needs during the 2 years. Adding
another crop, like millet, before wheat safely harvests the
surplus water while leaving enough for a successful
wheat crop.
Growers would plant foxtail millet as a forage for
livestock. Proso is grown for its grain.
"One foxtail millet variety, Golden German, provides
up to 6,100 pounds of dry matter per acre. That compares
with about 3,800 pounds from Manta, another variety,"
says Anderson. He is an Agricultural Research Service
agronomist at the Central Great Plains Research Station
near Akron, Colorado.
But Manta provides 13 percent total protein versus 10
percent for Golden German and two other varieties,
White Wonder and Butte. Manta also matures up to 3
weeks earlier than the other three varieties. An earlier
harvest extends the period before the winter wheat is
planted. That allows more precipitation to accumulate
and thus helps ensure the success of subsequent crops.
Farmers could have their cattle graze foxtail millet that
is cut and left in windows. This would eliminate the cost
of baling, handling bales, storing them, and then feeding
to livestock.
Anderson cautions farmers that foxtail millet serves as
an alternate host for the wheat curl mite, the insect that
transmits wheat streak mosaic virus. Wheat streak can cut
yields by up to 50 percent. He recommends farmers spray
a herbicide or till soil to kill all millet plants after harvest.
This eliminates the mites and prevents future virus
transmission.-By Dennis Senft, formerly with 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,
e-mail *

Hypernodulating Gene
Found in Soybeans

By boosting nitrogen fixation in soybeans and other le-
gumes, farmers might be able to cut down on the nitrogen
fertilizer they apply to other field crops grown in rotation.
Agricultural Research Service scientists in the Plant
Physiology Research Unit at Urbana, Illinois, have identi-
fied a single gene that regulates hypernodulation in soybean
root systems. "We're now attempting to map the gene and
produce a soybean cultivar that has this trait and also pro-
duces high yields in the field," says plant physiologist
James E. Harper.
On their roots, soybeans and other legumes create nod-
ules that are tiny homes for a type of bacteria that takes
nitrogen from the air and enzymatically converts it to am-
monia that plants can use for growth and seed development.
Scientists speculate that the more nodules a plant pro-
duces, the more nitrogen is left in plant tissues to be re-
turned to the soil when the plant dies and decomposes. This
extra nitrogen is then available to a following crop.
Conventional soybean cultivars provide about 40 pounds
of residual nitrogen per acre. If hypernodulated soybean
lines were to double the residual nitrogen returned to the
soil, this would provide over half of the nitrogen needs of
most corn varieties.
ARS scientists know that the chemical signal to regulate
nodule formation in the soybean root comes from above
ground-from young leaves--during the first 4 weeks of
plant growth. But they don't know what the chemical is or
how it signals plant roots to regulate nodule number.
"If we can learn what this chemical is and how it works,
we can use the information to regulate hypernodulation in
soybean lines for commercial use," says Harper.
Hypernodulated soybean lines can circumvent the natu-
ral nodule suppression that exists in commercial cultivars.
For example, a typical commercially available soybean cul-
tivar generates 70 to 200 nodules on its root system during
the first 4 weeks of growth. A hypernodulated mutant soy-
bean generates up to 1,000 during the same period.
Harper proved by using rooted leaf cuttings that the hy-
pernodulation signal comes from young soybean leaves.
His research group also showed that the signal is common
between soybean and mung bean plants. They did this by
grafting a hypernodulated soybean shoot to a mung bean
root, inducing hypernodulation on the mung bean.
If scientists can identify the nodule control signal, they
may be able to induce hypernodulation in other legumes.-
By Dawn Lyons-Johnson, ARS.
James E. Harper is in the USDA-ARS Plant Physiology
and Genetics Research Unit, University of Illinois, 331
ERML, 1201 W. Gregory, Urbana, IL 61801; phone (217)
244-6670, fax (217) 333-6089, e-mail *

Agricultural Research/January 1998

Feeding Soil Microorganisms To
Reduce a Water Pollutant
Conservation tillage can cut the
risk that atrazine, a popular weed
killer, will reach groundwater. This
tillage approach leaves some or all of
the previous crop's stubble on the
surface. As the stubble decays, or-
ganic matter builds in the top soil
layer. Beneficial microbes that thrive
in the carbon-enriched topsoil can
break down atrazine before it leaches
into groundwater. Agricultural Re-
search Service scientists based in
South Carolina came up with the
finding when they examined how
various tillage practices affect atra-
zine's fate in Iowa glacial till soils
and South Carolina sandy coastal
soils. The research could lead to
more environmentally friendly farm-
ing practices. ARS scientists also
study herbicide leaching and runoff
at other locations including Belts-
ville, Maryland; Tifton, Georgia;
Ames, Iowa; Morris, Minnesota; and
Stoneville, Mississippi.
Jeffrey M. Novak, ARS Coastal
Plains Soil, Water, and Plant Re-
search Center, Florence, South Caro-
lina; phone (803) 669-5203, e-mail

Some Texas Wheats Don't Bow to
Hessian Flies
Two top wheat breeding lines for
Texas resist the Hessian fly. One line
has two bonuses: high yield and re-
sistance to leaf rust. Discovery of the
fly resistance by Agricultural Re-
search Service scientists is timely be-
cause the Hessian fly was first found
in west-central Texas in 1997. Long a
notorious pest in the central plains, it
entered the United States in the 18th
century. If the resistant lines continue
yielding well and have other desir-
able traits, growers may get new
commercial varieties within 5 years.
Until then, they can consider avail-
able varieties such as 2180. 2163.

..ocr.e- i paate

2165, 2157, and Pecos. These resist
the fly in west-central Texas and in
Kansas. But growers need to weigh
their other traits, such as disease re-
sistance and yield potential. In Texas
in 1997, Hessian flies damaged 95
percent of the 48,000 acres of wheat
in McCulloch County alone, with a
$2.45 million loss in yield, according
to estimates from a Texas A&M Agri-
cultural Extension Service agent.
Chemical treatment is expensive, so
resistant wheat varieties have tradi-
tionally formed the main defense
against the insect.
J. H. Hatchett, ARS-USDA Plant
Science and Entomology Research
Unit, Manhattan, Kansas; phone
(913) 532-4719, e-mail
jhatchet @ oz. oznet.ksu. edu

Hessian fly, Mayetiola destructor.

Computer Program Helps the Bee
Business Keep Buzzing Along
Beekeepers can turn to their PCs to
manage the business more profitably.
BK-ECONOMICS ("BK" stands for
beekeeping), a free computer program
available from Agricultural Research
Service scientists, includes a spread-
sheet to track loans and equipment,
labor, vehicle, and insurance expendi-
tures. Plus, it has a database compo-
nent to help beekeepers market
honey. The database holds 49 years of
state-by-state honey values and
average production from individual
bee colonies. This can help beginners
determine how much honey-and
money-they can expect. For
example, beekeepers in Georgia can

expect an average of 50 pounds per
year per colony; in California, 90
pounds. A colony is two or more
typical white boxes or hives, each
containing nine frames of honeycomb.
The program also helps beekeepers
locate apiculture specialists, calculate
loan terms, and simulate business
expansion. This can help beginning
apiarists decide whether to buy or
lease new equipment or to make do
until later. BK-ECONOMICS runs on
IBM-compatible and MacIntosh
computers and is available through the
researchers on 3-1/2-inch floppy disks.
Gloria DeGrandi-Hoffman, USDA-
ARS Carl Hayden Bee Research
Laboratory, Tucson, Arizona; phone
(520) 670-6481, e-mail or

C Supplements Deter Cataracts
New findings confirm that long-
term use of vitamin C supplements re-
duces the risk of cataracts. Seventy-
seven percent fewer early-stage cata-
racts appeared in women who took the
supplements daily for more than 10
years, compared to those who didn't.
Cataracts-a clouding of the eye's
lens-are believed to result from oxi-
dation of proteins within the lens. Vi-
tamin C prevents oxidation. The study
of 247 women was conducted by sci-
entists at an Agricultural Research
Service-funded research center in Bos-
ton, in collaboration with the Harvard
University Nurses Health Study. Sup-
plement users took at least 500 milli-
grams of vitamin C daily, in addition
to food and multivitamin sources. The
findings corroborate a 1992 report
linking 10-plus years of the supple-
ments with far fewer cataract surgeries
among nurses in the Harvard study.
Paul F. Jacques, Jean Mayer USDA
Human Nutrition Research Center on
Aging at Tufts University, Boston,
Massachusetts; phone (617) 556-
3237, e-mail

Agricultural Research/January 1998

U.S. Department of Agriculture PETER E HILDEBRAND
Agricultural Research Service FOOD & RESOURCE ECONOMICS DEPT Paid
63Room 408 Lane PO BOX 110240 agriculture
6303 Ivy Lane
Greenbelt, MD 20770 GAINESVILLE FL 32611-0240 95
Official Business
Penalty for Private Use $300
To stop mailing FE
To change your address ___ I
Please return the mailing label from
this magazine.


* *
Visit for the latest news and information com-
S ing from USDA's Agricultural Research Service.

Want to find a story that ran in Agricultural Research
S magazine last year? Go to
S key.htm and use your browser's find function to search for story titles, key-
Swords, or principal scientists that appeared in past issues.

Subscribe to Agricultural Research

for $29.00 per year ($36.25 foreign addresses)
Visa and Mastercard accepted.
Prices subject to change.

Fax your order: (202) 512-2250
Phone your order: (202) 512-1800
Order by mail: New Orders, Superintendent of Documents
P.O. Box 371954, Pittsburgh, PA 15250-7954

University of Florida Home Page
© 2004 - 2010 University of Florida George A. Smathers Libraries.
All rights reserved.

Acceptable Use, Copyright, and Disclaimer Statement
Last updated October 10, 2010 - - mvs