In Tennessee, growers go to weevil I roundups
and rodeos, where they collect weevils for re-release on their properties.
Since 1989, as part of a research program, weevils have been released along
roadways and in pastures at more than 300 sites in 61 counties. Growers
themselves have released weevils at several hundred more sites.
Not just any weevil, however.
Tennessee farmers and other landowners are propagating, collecting, and
releasing the head weevil, Rhinocyllus conicus Froelich, and the rosette
weevil, Trichosirocalus horridus (Panzer), which is native to Europe.
Musk Thistle Is the Enemy
These two types of weevils feed, develop,
and reproduce specifically on thistles and are quite fond of musk thistle,
Carduus nutans L.,an exotic plant which is actually classified as a noxious
weed in many parts of the United States.
The musk thistle was introduced
into Tennessee from Europe in the 1940s, and it invades pastures, croplands,
orchards, nurseries, highway and railroad right-of-ways, and urban landscapes.
Farmers and other landowners have battled
thistle infestations for several decades, primarily by using chemical herbicides,
mowers, and garden hoes. Unfortunately, these methods provide only localized,
temporary control, primarily because musk thistle grows in many areas that
are inaccessible, impractical, and uneconomical for herbicide use or mowing.
Even in well-managed areas,
plant reduction may be only temporary, as seeds from surrounding plants
may re-infest.
IPM Approach Began in 1989
Use of plant-feeding weevils to fight musk
thistle is part of a multiyear, interagency IPM program that was started
in 1989 because of concerns about environmental pollution, groundwater
contamination, and increased pesticide costs.
The project has involved
partnerships with the Federal Highway Administration, the Tennessee Department
of Transportation, the University of Tennessee Agricultural Experiment
Station, and the University of Tennessee Agricultural Extension Service.
It has been led by Jerome F. Grant and Paris L. Lambdin.
The program incorporates
use of chemical herbicides, mowing, and biological control agents (i.e.,
plant-feeding weevils). The feeding activities of the head and rosette
weevils reduce the musk thistle's reproductive capability, viability, and
survivability.
Plant-Feeding Weevils Now Well Established
Nine years after the program began, these
plant-feeding weevils are well established in Tennessee. Involvement of
growers is critical to the program's success, and these growers continue
to learn not only at weevil roundups and rodeos, but by attending education
and field days and county meetings, where they receive hands-on exposure
to weevil identification and biology-
Until weevils are established
in all thistle-infested counties in Tennessee, plant-feeding weevils will
be transferred from several field reservoir sites to other areas.
Program results to date show:
Program Expanded to Four States in 1993
Because of the regional impact of musk thistle,
this program was expanded in 1993 into a multistate, multi-institution/agency
project to include cooperators in Georgia, North Carolina, and Virginia
as well as Tennessee.
This regional project
emphasized farmer education technology transfer, and the functional integration
of research for sustainable management of musk thistle in ongoing farm
systems. In each participating state, weevils were collected from field
insectaries and released on farms, at nurseries, and along highways.
Savings similar to those
in Tennessee have been realized in these other states.
This regional IPM program
should provide a long-term, areawide economical and environmentally compatible
method of suppressing thistle populations in the southeastern United States.
Research was supported
by the Tennessee Department of Transportation, the Federal Highway Administration;
the University of Tennessee through its Agricultural Experiment Station;
and Sustainable Agriculture Research and Education/Agriculture in Concert
with the Environment, Southern Region.
 The
rosette weevil, Trichosirocalus horridus, has been widely released as part
of an IPM program against musk thistle. |
 Weevil
roundups and rodeos give growers hands-on exposure to weevil identification
and biology. As an extra benefit, growers receive weevils for release onto
other thistle-infested lands. |
For more information contact:
| Karen Vail
University of Tennessee Entomology and Plant Pathology Section P.O. Box 1071 Knoxville,TN 37901 (423) 974-7138 |
Ron Seward
University of Tennessee Entomology-Plant Pathology 605 Airways Boulevard Jackson, TN 38301 (901) 425-4718 |
