The Rural Voice, 1988-07, Page 19Guelph, works with "classical" biolo-
gical control methods: he introduces
enemies like parasites and predators to
control insects and weeds. Classical
biological control operates on the
premise that a pest is a pest because it
either has no natural enemies or those
present are not effective enough. By
finding an effective enemy and intro-
ducing it into the area, pest numbers
can be reduced to non -damaging
levels.
Finding a suitable enemy often
isn't easy. It may involve searching
many different areas of the world.
Exotic enemies are used in most cases
because the pests are usually exotic
themselves, accidentally introduced
from elsewhere. For example, efforts
to control the southern green stink bug
in Australia resulted in two separate
releases of parasites, one from Egypt
and one from Pakistan. When the
Egyptian parasite became established
but did not control the pest, another
search turned up a variety of the same
species in Pakistan. This second para-
site found the Australian conditions to
its liking and thrived. Full control of
the stink bug was won in the mid -60s.
Two Canadian pests, the alfalfa weevil
and the cereal leaf beetle, have been
controlled by similar methods.
Dr. Laing points out that in most
countries these sorts of importation
and release programs are tightly con-
trolled. In Canada, one must apply to
the Plant Quarantine Division of Agri-
culture Canada in Ottawa, giving rea-
sons why the insect is being imported,
why it is beneficial, how it is to be
shipped, and how it is to be handled.
When a permit is issued and the
shipment arrives, it is taken to a quar-
antine facility to be opened. These
facilities are completely sealed units,
even down to air supply, so if the
insects escape from their containers
into the room they still cannot escape
from the room. All live material is
reared in this room, Dr. Laing says,
and everything that comes out of the
shipment is examined. Unwanted
organisms are destroyed in an incin-
erator on the site. Only then can the
insects be taken to a laboratory for
experimentation. Another permit must
be obtained before the insects are
released, although the original import
permit may have a release clause.
If the insect is released, there are
three possible outcomes: it may not
survive, it may become established but
not decrease the pest population, or it
may become established and perman-
ently control the pest population. The
third outcome is obviously the aim of
classical biological control: to estab-
lish a self-sustaining system that
works forever, without human inter-
vention. This is the essence of biolo-
gical control: once it is successful, the
problem takes care of itself.
Dr. Laing is also involved with
another form of biological control:
the augmented release of a native par-
asite. Parasite numbers are artificially
increased in the lab and then released
back into the environment. The goal
is to increase the density, and the ef-
fectiveness, of the natural population.
This is the essence
of biological control:
once it is successful, the
problem takes care of
itself... .
The problem for industry
is that when a control
method is perfected, it
enters the public domain.
Industry cannot patent
the control organism or
govern it in any other
way to get a return on
its investment.
Dr. Laing is now working with
Trichogramma, a small egg parasite
which is used all over the world to
control pests. A North American
species is being tested for use against
the spruce budworm. The big differ-
ence between this technique and
classical techniques is that the control
is not permanent. The parasite must
be released periodically to keep the
pest in check.
In Winnipeg, Dr. Morris is work-
ing to increase insect diseases that
occur naturally. He's also inundating
crops using microorganisms in the
manner of an insecticide spray. Dr.
Morris has been instrumental in
developing the bacterium Bacillus
thuringiensis — Bt as it is commonly
called — for use against the spruce
budworm in forestry. He has now
turned his attention to agriculture, and
is developing strains and application
methods effective against crop pests.
He is also working with nematode
worms that are insect parasites.
Dr. Morris says that Bacillus
thuringiensis is a naturally occuring
pathogen which has been isolated
from many lepidopterous insects
(butterflies and moths). When grown
under certain conditions, the bacter-
ium forms a spore and produces a
toxic protein in crystal form. If the
crystal or the spore is eaten by a larval
lepidoptera, it destroys the lining of
the gut, killing the insect directly or
causing a bacterial infection that will
eventually kill the larva. The spore/
crystal complex of the variety kurstaki
is now being produced commercially
and can be sprayed onto crops to
control some lepidopterous pests.
Bt and other insect pathogens such
as viruses and fungi, Dr. Morris says,
are particularly attractive alternatives
to chemical insecticides because thay
have very little effect on non -target
parasites and predators. The effec-
tiveness of Bt, for example, is largely
dependent on conditions in the insect's
gut (which are governed by the
insect's physiology and the food it
eats), and so Bt generally does not
affect non -target life.
According to Dr. Morris, different
strains of Bt can be used against
different types of insects. The variety
isrealensis is toxic to mosquito and
blackfly larvae, and is being used
effectively in some provinces to
control these insects. Another strain
has been shown to affect the beetle
larvae, and Dr. Morris says that two
products — one for the control of the
Colorado potato beetle and the other
for the sunflower beetle — are close to
being marketed.
Nematode worms may also be an
effective way to control insects, Dr.
Morris says. The nematodes are
naturally occuring parasites of soil -
dwelling insects. Dr. Morris says they
are an interesting biological phenom-
enon because they carry bacteria toxic
to insects. The immature stages of the
JULY 1988 17