The parasitic wasp
Colpoclypeus florus attempts to sting a larva of the oblique-banded
leafroller. Click the image for additional information about
it.
Read the
magazine
story to find out more. |
Rose Gardens: A Thorny Problem for Pesky
Caterpillars By Jan Suszkiw January 7, 2004
Agricultural Research
Service scientists and cooperators are plotting a war of the roses against
apple leafrollers that plague fruit orchards.
Roses--the wild, multifloral kind--are the centerpiece of small
gardens that ARS and Washington State University (WSU) scientists are planting around orchards to
bolster spring populations of the parasitic wasp, Colypoclypeus
florus.
After mating, a female C. florus wasp crawls inside the
cocoon that envelops the apple leafroller's caterpillar stage and deposits
about 20 eggs. Several days later, her maggot-like brood emerge to suck fluids
from the caterpillar, killing it. During the spring, the scientists observed,
only a small percentage of an orchard's apple leafroller population is affected
by such attacks. But during the summer, C. florus can thin the pest's
ranks by more than 50 percent.
Since 1999, ARS entomologists Tom Unruh and Robert Pfannenstiel
and WSU colleague Jay Brunner have sought to overcome the wasp's springtime lag
using "habitat modification." The approach involves planting gardens of wild
rose and strawberry as a refuge for a secondary host of C. florus called
the strawberry leafroller. This doesn't introduce a new caterpillar threat to
orchards, but rather provides the wasp's brood with a host of a suitable size
that's critical to their winter survival.
The result is a bumper crop of new wasps emerging in the spring
to mate, migrate into orchards and attack their primary hosts, Pandemis
pyrusana and the oblique-banded leafroller. Both are pests of apples, pears
and cherries.
In heavily infested areas, apple growers may spray orchards with
insecticide two to four times a season to keep these caterpillar pests from
damaging fruit. But making the orchards more hospitable to the wasps in the
spring could diminish the need for spraying, according to Unruh, at the ARS
Tree Fruit
and Vegetable Insects Research Unit, Wapato, Wash.
A
longer
article about the gardens, now being field-tested in Washington and Oregon,
appears in the January issue of Agricultural Research magazine.
ARS is the U.S. Department of
Agriculture's chief scientific research agency. |