Illinois Natural History Survey Reports

              1
I LLINOIS
NATURAL
HI STORY
S U R V E Y
I N S I D E
Aphid Speciation on
Pinyon Pines
2
Early 1800s Land Cover
in Illinois
3
Urban Ecology, Part II
4
Land Use and Quail
Population Biology
5
Species Spotlight:
Mourning Cloak
6
Naturalist's Apprentice:
Nymphalid Search
7
Continued on back page
The goal of a biological control
program is to control a pest while
having a minimal effect on non-target
species. Past biological
programs based on this principle
have proven to be successful and
safe alternatives to conventional
control prac-tices.
There
is a growing
concern in
both scientif-ic
and public
forums, how-ever,
about
the impact of
introduced
biologi-cal
control
agents on
nontarget
hosts and na-tive
natural
enemies.
An insect
pest against
which many
natural en-emies
have
been released
is the gypsy
moth, Lymantria dispar. Acci-dentally
introduced into the east-ern
United States from Europe in
1869, the caterpillar stage of the
gypsy moth can cause damage to
500 species of trees and shrubs,
most notably oaks and aspen.
The parasitic wasp Pimpla dis-paris
was fi rst introduced for con-trol
of gypsy moth in the 1970s,
and continues to be released in
Illinois’ Got a Brand-new Bagworm Para-some
northeastern states. Female
P. disparis lay their eggs into the
pupae of moths. The larval stage
of the parasites kills the developing
moth and adult wasps eventually
emerge from the pupal case.
In hindsight, it is not clear why
P. disparis was considered a good
biological control agent suitable for
release. For instance, a parasite be-ing
considered for biological con-trol
should not have a very broad
host range, but P. disparis is a gen-eralist
and attacks members from
at least 13 moth families. Also,
parasitism rates of gypsy moth by
P. disparis are frequently minimal,
sometimes as low as 1–2%, which
further argues against the release of
this species.
P. disparis has steadily ex-panded
its geographical range
well beyond areas where the
gypsy moth has been detected.
Clearly, P. disparis is attack-ing
and surviving in nontarget
hosts. The effects of P. disparis
on nontarget moth populations
have not been documented and
little is known about the life his-tory
of this introduced parasite
in Illinois. Although the gypsy
moth is not established in central
Illinois, P. disparis is present and
is frequently recovered from the
evergreen bagworm, Thyrid-op-
A female parasitic wasp (Pimpla disparis) attempting to parasitize a bagworm inside its
bag. Photo by Michael Jeffords, INHS Offi ce of the Chief
Autumn 2002
No. 373