Putting the Bite on Plum
Curculio Weevils By
June 6, 2001
Anyone who has ever bitten into a "wormy" apple will appreciate
the efforts of Agricultural Research
Service chemist Fred J. Eller, who has developed and patented a pheromone
bait that can give fruit growers an early warning of plum curculio weevils.
Pheromones are chemicals secreted by animals, especially insects, that
influence the behavior or development of others of the same species, often
acting as a sex attractant.
Plum curculio weevils, Conotrachelus nenuphar, attack
apples, peaches, cherries, pears, apricots and plums in the southern and
eastern United States. Adult female weevils lay eggs under the skin of
developing fruits, causing yield loss and scarring. Normally, growers become
aware of the pests only after the eggs are laid, when a telltale "crescent
moon" blemish appears on the fruit. Once this moon appears, the fruit is
permanently scarred. The plum curculio is only one-quarter inch long, with a
brown and gray body, and a long snout. The female beetle lays her eggs inside
pome and stone fruit, causing "wormy" fruit.
Eller, based at ARS National Center for Agricultural Utilization
Research at Peoria, Ill., identified the pheromone released by the male
curculio weevil. The chemical attracts both female and male curculios. He
incorporated the chemical, called grandisoic acid, into a trap that was
originally designed for boll weevils by ARS researchers in Mississippi. Eller
placed several traps baited with the chemical attractant in orchards at blossom
time. He found significantly more weevils in the baited traps than in the
More work is needed to expand the use of the pheromone and to
add volatile compounds, such as fruit odors, to enhance the attractiveness of
the pheromone and capture weevils even at low densities. Currently, other
researchers at the ARS Appalachian Fruit
Research Station, Kearneysville, W.Va., are combining the pheromone that
Eller identified with apple odors to make a more attractive lure for the plum
Ultimately, a pheromone-baited trap may one day offer a reliable
monitoring tool to help growers reduce pesticide use by spraying only after
pest populations are detected and prior to significant crop damage. ARS is
seeking companies to license the technology.
ARS is the chief scientific research agency of the
U.S. Department of Agriculture.
Scientific contact: Fred J. Eller, ARS
New Crops and Processing
Research Unit, Peoria, Ill., (309) 681-6232, fax (309) 681-6686,