Pepper Weevils: New Trap Aids IPM
Entomologist Fred Eller places a pheromone-baited weevil trap
among bell pepper plants. (K5759-2)
Midspring comes to the Deep South and a vegetable grower hopes for bumper
crops of bell and jalapeno peppers. But a crop consultant hired for
troubleshooting examines a fallen pepper, cuts into it, and finds a pepper
Just one Anthonomus eugenii larva among 100 peppers could be a
harbinger of serious yield losses later in the season. For pepper
weevilslike their boll weevil cousins on cottonmultiply rapidly;
with life cycles of about 3 weeks, generations eventually overlap.
The consultant knows that unless something is done soon, more and more
damaged peppers will begin to fall to the ground and rot. Lightly infested ones
will be unmarketable. Who wants a weevil in a salad?
Enter the spray rigs. Though larvae munching inside the peppers won't likely
be stopped, spraying insecticide about once a week could kill the overlapping
generations of adult female weevils flying about.
But such frequent insecticide applications through the months-long harvest
season impede natural control of other pests. They also complicate the harvest
because of the waiting periods required between each spraying and picking
before workers can re-enter fields.
Juan R. Anciso, a Texas Agricultural Extension Service entomologist at
Edinburg, says pepper weevils often aren't discovered and sprayed soon enough
to save a crop. Last spring, in the lower Rio Grande Valley, some pepper fields
were plowed under unharvested, he says, losing growers hundreds of thousands of
The weevils destroy all types of peppers in southern-tier states and
throughout Mexico and Central America. Economic losses in the United States are
estimated at $23 million per year.
Now ARS scientists have taken the initiative in helping integrated pest
management (IPM) come front and center to the weevil war.
A new, commercially available insect trapping system detects pepper weevils
usually 2 or 3 weeks before field scouts find either the adult weevils around
plants or larvae in fruiting peppers.
"Developing an attractant/trap system that could reduce the need for
insecticides by defining when and if applications were neededthat was our
goal," says Robert J. Bartelt, an ARS entomologist at the National Center
for Agricultural Utilization Research (NCAUR) in Peoria, Illinois.
Anciso says each spraying that can be avoided often saves the grower about
$15 per acre in insecticide costs alone.
Seeking the Come-Hither Pheromone
Responding to the need for a synthetic attractant, entomologists Bartelt and
Fred J. Eller began research in 1990 to identify volatile chemicals produced by
They took the 1/8-inch-long adult weevils from their laboratory colony and
anesthetized them with carbon dioxide to determine the sex of each.
Then they collected and chemically analyzed the volatiles produced when
single weevils fed on jalapeno peppers.
By 1993, the scientists applied for a patent on a combination of six
chemicals that mimicked the pheromone released by male pepper weevils. Three of
the six commercially available chemicals were already being used as part of the
synthetic boll weevil pheromone.
The chemical mixan aggregation pheromoneis a signal to both
female and male weevils that a good source of food is nearby and other weevils
are already present. Field tests in Texas, California, Florida, New Mexico, and
Mexico proved that the pheromone in sticky traps had potential as a weevil
population monitoring tool.
The time was ripe for private industry to become involved in further
development of the pheromone for practical field use. ARS formed a cooperative
research and development agreement (CRADA) with Trece, Inc., of Salinas,
California, to determine the best component blend, dose, pheromone dispenser,
and trap design to use in commercial pepper fields.
As with four previous CRADA's, Trece teamed up with ARS entomologists and
chemists to try refining the invention into user-friendly and commercially
successful forms, combining expertise in engineering, manufacturing, and
"We had found the CRADA program to be really successful, and we saw an
opportunity to serve the pepper-growing industry," said Bill Lingren,
Though the pepper industry is small, it is one of the fastest growing, as
peppers are being used in many processed foods.
In mid-1994, as research continued on improving formulations for sticky
traps, the company reported sales had been brisk for its first Pherocon pepper
weevil trap, available to growers through agricultural supply firms.
The ARS technology, patented in late 1994, was licensed to Trece on an
"Experience we're gaining from pepper weevil research may someday prove
useful for IPM of related Anthonomus pests, including cranberry weevil,
strawberry bud weevil, and apple curculio," says Eller, who is now in the
NCAUR's Food Quality and Safety Research Unit.
If presently used insecticides become no longer commercially available
because of regulatory bans or because target pests become resistant to
insecticides, IPM that includes monitoring traps could take on greater
Each pepper weevil trap, containing only 10 milligrams of synthetic
chemicals, is designed to release about 10 millionths of a gram per hour and to
monitor up to a hectare, which is about 2.5 acres.
Other IPM-oriented pepper weevil research is being conducted by ARS
entomologist Donald A. Nordlund in Weslaco, Texas. He says at least seven
parasites attack the pest, including Catolaccus hunteri, a cousin of the
C. grandis that feeds on boll weevils. [See "Evicting the Boll
Weevil," Agricultural Research, March 1994, pp. 4-10.]
If an artificial diet for C. hunteri or some other parasite can be
developed, it may be possible to mass-rear and release them so they can prevent
the usual buildup of pepper weevils as the season progresses. This control
approach is known as augmentation.
Alternatively, mass releases of the parasites after pepper crops have been
harvested may suppress weevil populations in wild plant hosts, such as
nightshades, before the next growing season.
Feasibility studies on mass release of parasites to control pepper weevils
may encourage commercial parasite rearing. Nordlund notes that production of
natural enemies of pest insects is an expanding industry.
While pepper growers look forward to new biological control technology,
keeping a close watch on weevil populations so as to make insecticide
applications more efficient is the most environmentally friendly development so
far, says Eller. -- By Ben Hardin, ARS.
Bartelt is in the USDA-ARS
Bioprotection Research Unit, and
Eller is in the
Food Quality and
Safety Research Unit, National Center for Agricultural Utilization
Research, 1815 N. University Street, Peoria, IL 61604; phone (309) 681-6541.
"Pepper Weevils: New Trap Aids IPM" was
published in the April
1995 issue of Agricultural Research magazine.