Joint Venture Pays Ag Dividends
Entomologist Robert Jones examines a weevil species closely
related to the boll weevil. It was collected from flower buds on a Hampea
longipes tree in Mexico.
U.S.-Mexico research nets benefits in pest management, crop improvements on
both sides of the border.
Pilot Rene Davis tips the black nose of the sleek Aero Commander down toward
the river snaking through the pancake-flat land 1,000 feet below.
"It used to be called Rio de las Palmas, the River of Palms," his
voice crackles through the headphones, barely audible above the roar of the
Through the early morning mist, there's no great abundance of palms to be
seen lining the silvery river, but the water's span also looks a bit too slim
to warrant its modern name: Rio Grande, the big river. From our bird's-eye
view, the Rio Grande looks no more than a stone's throw in width, the watery
equivalent of a backyard fence where neighbors lean to exchange informative
In recent years, quite a few scientists with USDA's Agricultural Research
Service have been "going to the fence" on a regular basis to talk to
their Mexican counterparts about problems that affect the land on both sides of
the Rio Grande.
There's always plenty to talk about, according to Edgar G. King, Jr.,
director of the ARS Subtropical Agricultural Research Laboratory.
Pilot/photographer Davis works at this Weslaco, Texas, lab just 7 miles from
the U.S.-Mexico border.
Entomologist Juan A. Morales-Ramos checks on the health of
adult Catolaccus grandis wasps emerging from their pupae. They will be
used for testing in laboratory and field experiments.
"Within about 80 miles of Weslaco, there are nine bridges and a ferry
crossing that link the United States to Mexico," says King. "A lot of
agricultural products go back and forth over those bridges every day.
"By working with the scientists in Mexico and sharing
information," he says, "we benefit U.S. consumers by ensuring the
agricultural commodities that come in are high-quality and safe, at a
reasonable price, and in good supply. At the same time, our research
facilitates the export of products such as apples to Mexico.
"For many years, there have been people like Whetten Reed of USDA's
Foreign Agricultural Service and Luis Galan Wong of Mexico's Universidad
Autonoma de Nuevo Leon (UANL) at Monterrey, who have understood the value of
this cooperation and worked hard to make it happen."
Entomologist Robert W. Jones, who is working on biodiversity studies at El
Colegio de la Frontera Sur in Chiapas, Mexico, concurs on the importance of
cooperative efforts across the border.
"Insect pests do not recognize political borders," Jones notes.
"This means that to manage insect pests most effectively and with minimal
environmental impact, we must consider both sides of the border as a single
Adds insect geneticist Nina M. Barcenas Ortega, "Mexico is the home of
many natural enemies that control native pests in their natural environment.
Collaborative research with American scientists allows the discovery of
potential natural enemies for the development of sound integrated pest
Barcenas is with Mexico's Colegio de Postgraduados en Ciencias Agricolas,
which is located just east of Mexico City, at Texcoco.
U.S. and Mexican scientists are working together on a
technology for eradicating the Mexican fruit fly. Here, Mexican citrus grower
Antonio Cantu (left) and ARS entomologist Donald Thomas (second from left)
oversee culling of oranges bound for a juice plant.
A classic example of border-crossing pests is the boll weevil, estimated to
cost the U.S. cotton industry $300 million annually.
"The cotton that we grow in the lower Rio Grande Valley originated in
Mesoamericathe Mayans and Aztecs used cotton fiber in their
clothing," says King. "And the boll weevil originated in southern
Mexico and parts of Central America, most likely on a tree called
When, in the early 1890's, the boll weevil migrated northward to begin
gnawing its way across the U.S. Cotton Belt, it was not, unfortunately,
followed by any of the natural enemies that kept it in check on its native
It wasn't until 1967 that USDA scientists brought from Mexico a little wasp
with the big name, "Catolaccus grandis," as a potential
biological control against the weevil. [See also "Evicting the Boll
Weevil," Agricultural Research, March 1994, pp. 4-10.]
Tiny C. grandis displayed an impressive appetite for boll weevil
larvae. But because practical means of rearing the wasp on boll weevils
appeared to pose an insurmountable problem, there was no interest in
The starting point for a workable wasp diet, King believed, was a solid
biological understanding of the wasp itself. That came to the Weslaco lab via
Juan A. Morales-Ramos, a Mexican entomologist who is now with ARS on a
The task of developing a wasp diet was first tackled by ARS entomologist
Antonio A. Guerra, in collaboration with scientists and students from the
Universidad Autonoma de Nuevo Leon at Monterrey.
Since September 1993, the artificial diet has been sufficiently improved at
Weslaco by visiting Mexican scientist M. Guadalupe Rojas, Morales-Ramos, and
King to produce wasps for field releases. This achievement is an important
milestone in the biological control world.
This type of U.S.-Mexican teamwork in science isn't new. And it's not even
particularly unusual, according to Charles A. Onstad, director for ARS'
Southern Plains Area, headquartered at College Station, Texas.
"In the early 1990's, Floyd Horn [then director of the ARS Southern
Plains Area and now USDA deputy undersecretary for research, education, and
economics] asked all ARS scientists to document activity they had going on with
Mexico," Onstad recalls. "He received a list of 50 or 60 projects
that were already under way in ARS labs all over the country."
Among the leaders was the Weslaco lab, which has a long history of
outstanding cooperation with Mexico's UANL, according to UANL Secretary General
Reyes S. Tamez Guerra. "These cooperative research efforts have resulted
in the training of new Mexican scientists, as well as the implementation of new
technologies in the field of biological control of insect pests that damage
several crops important to both countries," he says.
The flourishing U.S.-Mexico scientific partnerships became more formal,
beginning in 1993 with a series of meetings between the national program staffs
of both USDA and its Mexican equivalent, the Secretaria de Agricultura,
Ganaderia, y Desarrollo Rural.
"Our scientists have gone to Mexico, met their scientists, and toured
their facilities. Mexican scientists have come here to work with us on problems
of mutual interest," says Onstad. "It's an equal partnership."
As part of a joint experiment with ARS scientists at Weslaco,
Jesus Vargas, an entomologist with INIFAP's Rio Bravo Experiment Station, will
release these parasitic wasps in Mexican cotton fields.
Another prime example of this partnership is the cotton breeding effort
under way by ARS plant geneticist Charles G. Cook. Although Cook is based at
Weslaco, he often works at Las Huestecas, near Tampico on Mexico's eastern
There, in cooperation with Ernesto Salgado of the Institute Nacional de
Investigaciones Forestales y Agropecuarias (INIFAP), Mexico's equivalent of
USDA's Agricultural Research Service, Cook is trying to develop fast-growing
cotton that might "outrun" some pest attacks.
"That far south in Mexico, they don't plant cotton until June or July.
So when the cotton comes out of the ground, the insects are sitting there,
waiting," Cook says. "If we could get cotton in and out quicker, we
could reduce the amount of chemicals farmers have to spray to fend off those
Cook and Salgado have produced several very short-season lines, including
Texas 121, which offers another advantage of importance on both sides of the
"The leaves are hairless. This makes the plant less hospitable to
whiteflies, because a plant's hairs give the insects someplace to attach their
eggs and provide anchors for the larvae," Cook explains.
ARS entomologist Jimmy R. Raulston has long had his eye on a different
pest: Helicoverpa zea. Also known as the corn earworm, cotton bollworm,
soybean podworm, or tomato fruitworm, it costs U.S. farmers nearly $1 billion
annually in crop losses and control expenses.
"There's a major migration of as many as 7 billion corn earworm moths
out of Mexico's Rio Bravo area, usually in early June," says Raulston, who
is based at Weslaco. "Rio Bravo is Mexico's biggest irrigated corn-growing
region, with about half a million acres of corn planted each year." In
Mexico, the Rio Grande is called Rio Bravo.
To gauge the threat to crops and provide an early warning to U.S. growers,
Raulston and Jesus Loera, an INIFAP entomologist at Rio Bravo in the Mexican
state of Tamaulipas, routinely take soil samples from up to 120 Mexican fields,
checking for developing earworm larvae. When those larvae mature into airworthy
moths, the corn in the Mexican fields will be too old for their tastes, so
they'll head for greener crops in the United States.
Raulston and fellow ARS entomologist Dale W. Spurgeon are also spending time
these days investigating the boll weevil.
Nina M. Barcenas Ortega (left), an insect geneticist at
Mexico's Colegio de Postgraduados, and student Victoria Gomez Tovar work with
USDA agencies to develop insecticide-resistant Catolaccus grandis wasps.
"Cotton producers in Texas plow down their harvested fields in
September, and there's no cotton available for the insects until March or
April," says Raulston. "So the weevils are without a host during a
cool spell and go into diapause. That's a period of temporary dormancy, when
normal development is arrested," he explains.
"But down in southern Tamaulipas, cotton is harvested in December and
January and not planted again until June or July, so those weevils have to get
through a hot, dry spell with no host plant. We need to find out the survival
mechanisms of the Mexican weevils and whether they might come to the United
States and interfere with efforts to eradicate the weevil here."
In cooperation with Loera, Raulston and Spurgeon have begun trapping boll
weevils at 18 locations across Tamaulipas. A second set of traps is operated by
INIFAP entomologist Jesus Vargas. Several of the traps are near Mexican schools
where teachers and students help collect the insects for closer study at
Weslaco and at ARS' Areawide Pest Management Laboratory at College Station,
Craig L. Wiegand takes a broader view of Mexican agricultureusually
from about 400 miles up in space. A soil scientist in the ARS Remote Sensing
Research Unit at Weslaco, Wiegand has used satellite images to determine soil
salinity and agricultural potential of Mexican farm fields.
"In Mexico, there are about 14.8 million acres of irrigated land, of
which about 4.9 million acres are salt-affected," Wiegand explains.
"Salt is always naturally present in soil and in irrigation water. If you
don't add enough water to leach the salt down, it gets left in the root zone.
At the same time, if you over-irrigate soils that are poorly drained, a shallow
saline water table forms."
Evidence of the salt's impact is visible in LANDSAT satellite images that
register healthy plants as a deep-red color, with troubled areas depicted as
Weed scientist James Smart (right) checks the condition of a
cotton plant in conservation-tillage plots at the ARS Subtropical Agricultural
Research Laboratory's north farm with grower Juan Minana (center) and Jaime
Sanches, president of the Impulsora Agricola de Matamoros, S.A. de C.V.
"We've been doing this kind of work with sugarcane in the United States
since about 1992," Wiegand says. "Scientists from the Mexican
Institute of Water Technology at Jiutepec saw our work and asked us to work
In early 1994, Wiegand went to Mexico and helped select wheat fields there
for use as benchmarks. The fields' soil salinity and grain yields were
measured, then compared with satellite images to calibrate the images with the
By running digitized information from the images through a production
equation, the scientists translated the satellite's pictures into potential
yield figures for all the wheat fields in an irrigation district.
"Being able to show the salinity in a field helps the farmer decide
what to grow in that field," Wiegand says. "For example, wheat's more
tolerant of salt than corn and can be grown in fields where corn won't
Leonard Lane's interest in Mexican soils is more down-to-earth. A
hydrologist at ARS' Southwest Watershed Research Center at Tucson, Arizona,
Lane has been studying Mexico's challenging Tepatate soils since the late
"When the good soil in Mexico's highlands erodes, the volcanic ash
that's beneath it solidifies like soft concretethat's Tepatate,"
"The farmers have to go in and break it up with bulldozers, then
pulverize it. It will grow things, but not too well. Our problem is how to
build the soil back up with long-term sustainable agriculture."
Information on the Tepatate soils of Mexico will be incorporated by ARS soil
scientist L.D. Norton into USDA's Water Erosion Prediction Project (WEPP) at
the ARS National Soil Erosion Research Laboratory at West Lafayette, Indiana.
Assisted by Celestino Cervantes (left), entomologist Donald
Thomas checks grapefruit for exit holes made by Mexican fruit fly maggots. This
information will help assess the effectiveness of wasp parasites released at an
INIFAP experiment station near Montemorelos.
"The purpose of WEPP is to predict erosion of various types of
soils," says Lane. "Moving into these areas of Mexico gives us
additional information for the database."
Licking the Tickand Fruit Flies and Bee Mites
While much media attention has been lavished on the northward advances
through Mexico of Africanized honey bees, those aren't the only winged denizens
of Central America to capture ARS scientists' attention.
Back at Weslaco, entomologist Robert L. Mangan and coworkers in the Crop
Quality and Fruit Insects Research Unit are concentrating on ways to combat
fruit flies on crops ranging from citrus and avocados to more exotic mangos,
guavas, and other tropical fruits.
"We have a field station at General Teran in the Mexican state of Nuevo
Leon where we study the natural fruit fly population, test traps and sampling
methods, and do anything that involves large numbers of insects," says
"The Mexicans have also paid for us to build a forced hot-air chamber
in Tapachula to do work on guava, which they're interested in," he says.
To manage honey bee parasitic mites and document Africanization
of domesticated and feral honey bees, Mexican beekeeper Jose Santos Rodriguez
collaborates with ARS researchers at Weslaco.
"You can bring citrus, mangos, and most other fruit into the United
States and do the research here. But guava is so heavily infested with fruit
flies that it can't be brought in, so the chamber had to be built down there.
We already know hot air will kill the insects. We just don't know what the
product will be like after that treatment," says Mangan.
ARS and Mexican scientists have also teamed up to combat pesticide-resistant
ticks on cattle and tracheal and varroa mites in honey bees.
"In Mexico, the southern cattle tick, Boophilus microplus, has
developed resistance to organophosphates and pyrethroids," notes
entomologist John E. George, who is in the ARS Tick Research Unit at Kerrville,
"Right now, coumaphos is the only approved chemical for use in
cattle-dipping vats at the U.S. Mexico border. If pesticide-resistant ticks
were to be introduced across the border, we could lose control of these
disease-spreading ticks rather quickly."
Before scientists can study pesticide-resistant ticks to see what makes them
different, they must be able to quickly identify the pests. But current tests
can take as long as 90 days to provide that identification.
"We started work about 2 years ago with INIFAP and Texas A&M
University on developing molecular probes to detect whether a tick has the
genes for pesticide resistance," says George.
"Also, the ARS Veterinary Entomology Laboratory at College Station is
trying to determine the biochemical mechanisms that enable ticks to be
resistant. I'm hopeful that within 3 years we'll have a probe that could give
us the identifications we need in just a few days."
The Weslaco lab plays a key role in monitoring changes in populations of the
much-publicized Africanized honey bee.
"We had a trap line along the U.S.-Mexican border and in central
Tamaulipas, about 150 miles south of the border," recalls insect
geneticist Anita M. Collins, formerly head of the Honey Bee Research Unit.
Manuel Giron holds a plastic bag containing weevil-infested,
male floral buds collected from a Hampea longipes tree in the Chiapas,
"Originally, the intent was to study the process of Africanization of a
honey bee population. But the traplines also served as an early warning system
for the United States, as far as the location of the Africanized bees. Now,
from a scientific standpoint, we want to know how much interbreeding of
Africanized and European honey bees is occurring in the Mexico-Texas
Body size measurements of captured bees are made in a Mexican lab in Ciudad
Victoria. Then sampled bees are sent to Weslaco, where scientists use
ARS-developed computer software to compare the bees for distinctions ranging
from wingspans to differences in their honeycomb wax.
Mexico made bee history of another kind in 1980, with the discovery there of
the first tracheal mites in the Western Hemisphere outside of Brazil and
"Tracheal mites have been in bees in Europe since at least the turn of
the century," says entomologist William T. Wilson of the Honey Bee
"But they eventually got into Brazil and Colombiaand finally
Mexicothrough people bringing in queen honey bees, probably from
Within a few months of Wilsons initial report in 1980 of the arrival
of tracheal mites in Mexico, they had spread to half of Mexico's 32 states. By
1984, the mites were in U.S. bee colonies, where they now cause millions of
dollars in damage annually.
Entomologist Guadalupe Rojas, co-inventor of an artificial diet
for Catolaccus grandis, displays a unit used in rearing this biocontrol
In 1984, working with commercial beekeeper David Cardosa at Allende, Nuevo
Leon, Wilson developed a treatment to kill the mites as bees breathed menthol
vapors in the hive. Later, Wilson worked with Celina Garza of the Universidad
Autonoma de Nuevo Leon on use of formic acid, a synthetic version of a
component of bee venom, as a fumigant against the mites.
"In all these various projects, we're looking for ways to more
efficiently and economically protect American agriculture from exotic problems,
promote export of U.S. products, and meet consumer demand for a wide array of
food and fiber products," says deputy undersecretary Horn.
"Mexico is our neighbor. The Mexican people are a significant market
for us, and clearly their fate is tied to ours. There are many advantages to
this type of scientific teamwork." By Sandy Miller Hays,
Mangan is at the USDA-ARS
Agricultural Research Laboratory, 2413 East Highway 83, Bldg. 200, Weslaco,
TX 78596; phone (956) 447-6316, fax (956) 447-6345.
E. George is at the USDA-ARS
Insects Research Laboratory, 2700 Fredericksburg Rd., Kerrville, TX,
78029-9184; phone (830) 792-0303, fax (830) 792-0302.
Watershed Research Laboratory, 2000 East Allen Road Tucson, AZ 85719.
"Joint Venture Pays Ag Dividends" was
published in the September 1995 issue of
Agricultural Research magazine.
A Diet As Good As the Real Thing
The first essential for devising an appropriate artificial diet was
knowledge about the chemical composition of immature boll weevils, the
preferred diet of the Catolaccus grandis wasp.
Entomologist Guadalupe Rojas and ARS scientists learned that this parasitic
wasp applies a venom to its host that changes the host's chemical makeup so it
never matures. The venom also liquefies the internal portion of the host,
making it easier to consume and digest.
The scientists have now simulated the composition of the liquefied boll
weevil with synthetic chemicals. Feeding tests show that C. grandis
wasps find the simulation to be acceptable. Using the artificial diet is
greatly simplifying the mass-rearing of this biocontrol agent for boll weevils.
A patent application has been filed for the artificial diet and rearing
system. A cooperative R&D agreement with Integrated BioControl Systems of
Lawrenceburg, Indiana, will speed commercial development.