| What Tumlinson found were four
compounds that, in combination, were as attractive to female boll weevils
as live males were. None of the compounds was active alone, which had
made isolation and purification more difficult.
Isolating a pheromone in 1969 was still new research territory, and
the equipment was not very sensitive. Tumlinson had to isolate about
10 milligrams of each compound to characterize it; today, compounds
are routinely identified from 1 microgram and sometimes even from 1
nanogram, a 10,000- to 10-millionfold reduction in sample requirements.
Tumlinson recounts, "To get enough of each compound to determine
the structure, I eventually extracted and steam-distilled 54 kg of boll
Hardee christened the pheromone complex Grandlure, which continues
to be one of the four or five most effective pheromone lures in commercial
During the same period, Joseph E. Leggette, who was then with the BWRL,
made a quantum leap forward in trap design, creating an effective live
trap from an inverted floral paperliner. Several more generations of
refinements were made by a number of ARS researchers until they came
up with the design still being used today. More than 20 million of these
traps have been used in the United States since1987.
"Growers had just been waiting for us to come up with these two
tools to dig into planning an eradication program," Hardee explains.
With a trap and a lure, insecticide use could be targeted to boll weevil
appearance in cotton fields.
Using Biology Against the Boll Weevil
The boll weevil eradication program depends primarily on detection
and carefully targeted insecticide use, unlike the screwworm program
to which it is often compared but which depended on biological controlreleasing
sterile male insects to prevent reproduction. But it was Knipling's
advocacy in both programs for research to understand the two pests'
biology and ecology that laid the groundwork for so much of the boll
weevil eradication program's success.
Researchers had to learn and are still learning about such traits as
how far boll weevils will travel, especially in the face of strong winds;
what other plants attract them; and the insects' diapause, or winter
An ARS team led by Edwin P. Lloyd at BWRL focused on finding a way
to use diapause as an effective time to reduce the boll weevil population
while reproduction slows. In 1968, the team conducted a 5,000-acre "reproduction-diapause"
control technique demonstration in Mississippi. It successfully used
for the first time a system of targeting insecticide applications to
diapausing boll weevils and monitoring pheromone traps.
ARS researchers then gathered all the available researchtheirs
and that of many other scientistsand built a model of an areawide
eradication system that would eliminate boll weevils. The next step
was to find a large cotton-growing area, convince the growers to participate,
and start eradicating boll weevils.
A pilot test of control techniques was run in southern Mississippi
and adjacent cotton growing areas in Alabama and Louisiana from 1971
to 1973. For the first time, it was shown that boll weevil eradication
was finally technologically feasible.
Then, with the support of the National Cotton Council and the approval
of the majority of local growers, a 3-year Boll Weevil Eradication Trial
began in Virginia and northern North Carolina in 1978, conducted by
APHIS with research support from ARS.
The trial proved to be an overwhelming success and established the
operational strategy for all future programs as they spread throughout
"The model that ARS developed has been the key to success in each
new state as growers voted to go for eradication," says Charles
T. Allen, program director of the Texas Boll Weevil Eradication Foundation.
"There has always been so much politics and contention in cotton
production. If the plan hadn't come from ARS and other collaborators,
I'm not sure that growers would have had as much confidence in the possibility
Allen worked for the Texas Agricultural Extension Service with cotton
growers for 20 years before joining the Texas foundation. Until he saw
the eradication program in use, he could hardly believe that he would
ever see the day when the boll weevil would be eliminated. "Now
I think I will see it to completion before the end of my career,"
Costs and Payoffs
At one time, cotton growers applied more than 41 percent of all insecticides
in agricultural use; they regularly sprayed their cotton as many as
15 times a season. In the first season of an eradication program, an
average of seven or eight insecticide applications are timed for the
fall, just before diapause. In subsequent years, insecticide application
is based on finding boll weevils in traps, with an average of five applications
in the second year and only two in the third year.
"Eradication is expensive to begin with, but the payoff is tremendous
as the program moves along," explains Frank Carter of the National
Cotton Council of America. "Early on, our studies showed about
a 12:1 benefit-to-cost return to the cotton industry for every dollar
invested in eradication."
But the economic payoff is really just starting, he points out. Pesticide
costs continue to decrease as eradication succeeds in more and more
states. There will be generations of cotton growers who may never have
to spray for boll weevils. "Every year that happens will be a payoff
of this program," Carter adds.
One ARS contribution in the mid-1990s that helped the economic viability
of the program was finding that lower doses of malathion, the only insecticide
currently used for eradication, are just as effective as higher ones.
This decreased the cost of the program dramatically.
In addition to significantly lower control costs, there are environmental
benefits of trading weekly spraying by individual growers for nationwide
eradication. By reducing the amount of pesticides being used as the
eradication program succeeds, more beneficial insects survive to protect
cotton from other pests. As the ecosystem changes, researchers have
had to conduct additional studies to ensure that no new problems are
created for growers in place of the boll weevil.
There have even been some unexpected payoffs of ARS boll weevil research.
In January 2002, after checking out new ARS research on the boll weevil's
inability to survive in or on compacted cotton bales, APHIS and Peruvian
agricultural officials reached an agreement to remove the mandatory
fumigation of U.S. cotton bales with methyl bromide to prevent spread
of boll weevil. Curtailing fumigation will significantly reduce the
cost of exporting cotton to Peru. A similar agreement has been reached
with Colombia, and discussions are being held with Pakistan and other
Finishing the Job
Although the eradication foundations are closing in on final success,
there remain several major issues on which ARS continues to conduct
research, says entomologist Dale W. Spurgeon with the ARS Areawide Pest
Management Research Unit, College Station, Texas. Spurgeon is also ARS'lead
scientist for the agency's boll weevil efforts.
One issue is the impact of conservation tillage, also called no-till,
on the eradication program. "We have some indications that boll
weevil survival is different in no-till," Spurgeon says. "We
need to understand and adapt to the effects of no-till as it becomes
a more common practice in eradication zones."
Another issue left for research is completing a DNA fingerprint library
of boll weevils so that when one reappears in an eradicated area, its
source can be identified. This will also help identify the most effective
locations for detection traps.
And the effect of weather, especially of extreme events like hurricanes,
on the potential for the boll weevil to reenter the United States from
Mexico also needs study.
"Understanding how and why control measures work is essential
to the continued progress of eradication," Spurgeon says. "If
we don't know why something happens, how can we be ready to correctly
tweak the eradication model to deal with it?"
But Spurgeon and the other ARS boll weevil researchers have created
a Catch-22 for themselves. The program has just about eradicated them
out of places to do their research. Once the boll weevil has been eliminated
from a state, they can't do research there anymore. That's because they
they don't want to inadvertently reintroduce the insect.
"I can't say I'm too upset at the prospect, since complete eradication
has been our goal for so long," he says.By J.
Kim Kaplan, Agricultural Research Service Information Staff.
This research is part of Crop Protection and Quarantine, an ARS
National Program (#304) described on the World Wide Web at http://www.nps.ars.usda.gov.
To reach people mentioned in this article, contact Kim
Kaplan, USDA-ARS Information
Staff, 5601 Sunnyside Ave., Beltsville, MD 20705-5128; phone (301)
504-1637, fax (301) 504-1648.
What a Difference No Boll
The year before boll weevils marched into Georgia in 1915, the state
produced 2.8 million bales of cotton. Less than 10 years later, Georgia's
annual cotton production had fallen to 600,000 bales. By 1983, Georgia
cotton production was down to 112,000 bales harvested from 115,000 acres.
But in 1987, Georgia began a boll weevil eradication program. A decade
later, in 2000, cotton production in Georgia had rebounded to 1.66 million
bales. In this one state alone, the cotton industry, including farms,
gins, warehouses, cottonseed oil mills, and textile mills, provides
53,000 jobs and has an overall economic impact of more than $3 billion
Fear No Weevil
Marshall Grant and his family have been growing cotton in North Carolina
since the 1780s. But boll weevils almost put him out of business between
the environmental and economic costs of control.
"We were spraying insecticides every 5 days until the bolls were
mature. Now that boll weevils have been eradicated from the Carolinas
we're down to an average of one, maybe one and a half sprayings per
year for other pests," Grant says. "The eradication program
has made the difference between there being cotton production here and
there not being any cotton production in North Carolina."
"We Don't Cotton to Boll Weevil Round Here Anymore"
was published in the February
2003 issue of Agricultural Research magazine.