Other advantages to the implementation of
biological controls are
environmental and economic sustainability.
Classical biological control is
causally in the short term
as it can be expensive and time-consuming to produce,
evaluate, and transport
biological control agents to release sites.
However, if populations of
natural enemies becomes
self-sustaining in the new habitat,
the cost of control decreases.
In comparison, the cost of
augmentative biological control remains
about the same over time
as augmentative biological control generally
involves multiple introductions of the control agent.
Conservation biocontrol can be quite
affordable as the measures taken in
this approach do not include
direct manipulation of the population of natural enemies.
Overall, the future of biological control seems bright.
New technologies that make biological control
more economical are constantly being developed.
These include the use of
mechanized applicators as well as banker plants,
which provide additional resources to
support populations of beneficial insects.
In addition, the development of
new highly specific insecticides allows
the integration of
biological controls with chemical controls,
and promote the integration of
biocontrol into IPM systems.
Despite the many advantages of biological pest control,
this approach is not without its limitations.
First, like most integrated pest management tactics,
biological control requires a thorough understanding
of the biology and
ecology of all species within
the habitat prior to implementation.
Understanding these factors is necessary to
ensure the efficiency of biological control.
For example, annual cycles of
temperature and day length may affect the ability of
a natural enemy to control pests in
the year round crop production of many greenhouses.
A short day length may limit
the efficiency of visual predators,
while some natural enemies
have obligatory [inaudible] requirements,
and can only be suitable control agents
at specific times of the year.
Lack of information about
the target pest and its natural enemies can inadvertently
result in unintentional and unexpected damage
to both natural and managed systems.
Unfortunately, there are several instances
where a lack of research has
resulted in a biological control system
that has backfired on the manager.
Take for instance, the case of the Asian ladybird beetle.
This predator was originally
imported into North America as
a biological control agent for
aphid pests throughout the 20th century.
The beetle helped to suppress aphid populations,
but they also ended up competing
with native ladybird beetles.
Due to the Asian lady bird
beetle's high reproductive capacity
and resilience to environmental extremes,
this introduction has resulted in an ecological shift.
The Asian ladybird beetle is now one of
the predominant lady bird species
in many regions of North America.
If a biological control agent has abroad diet range,
its impact on the pest can be diluted through
the consumption of non pest species.
Parasitoids and predators that are host specific are
generally more effective as biological control agents,
as they will efficiently search out and attack
specific pests with little impact on non-target species.
On the other hand,
the use of biological control agents
with a restricted host range,
may mean that multiple species are
required to control a pest complex,
which can increase the cost of management.
The diversity of plants grown in
some agroecosystems can further
complicate the use of biological controls.
Many nurseries can have over 1000 cultivars
of different plants growing in the same facility.
This means there will be a greater diversity
of pests to be controlled,
many of which may not be controlled
by commercially available agents.
The release of multiple
biological control agent needs to be
specifically timed in response to
pest phonology and population densities.
If other types of control tactics are
used to control some of the pest species,
they will need to be compatible with
the biological control agents.
Natural enemies of different species
can also interfere with each other.
They may compete for resources or be vulnerable
to predation by the other natural enemies.
These interactions get more complex as
plant and pest diversity increases.
