Biological Insect Controls
The ultimate goal in treating harmful insects in the landscape is
reducing the risk of insecticide exposure to people and animals through
alternative controls.
One of those controls is the use of certain biological organisms,
byproducts of biological organisms and products that affect the growth
and development of pests to manage pest populations.
Several of these natural organisms have been isolated and harnessed
for use in order to control a variety of agricultural pests.
Natural predators
Predators are the most recognized biological control organisms. These
are active hunters that are usually larger than their prey and they
must consume large quantities of prey to complete their life cycle.
They play a limited but important role in pest management.
The most commonly recognized predators are lady bugs and lacewings.
Lady bugs typically
prey on all stages of aphids, scale insects and spider mites. Lacewings
feed primarily on aphids.
Predators do not typically produce the rapid results homeowners expect
and therefore may not be aesthetically acceptable. Other limitations
include the need for hundreds of predators to effect any major control.
Parasites
These are organisms that live in or on another organism (called the
host) typically to the parasite's benefit and the host's detriment.
Wasps develop inside the host after eggs are laid in or on the host
by the female wasp.
Parasites are more efficient biological controls because they are
host specific.
The use of insecticides should be carefully managed when parasites
and predators are present to avoid disrupting the natural predator
prey balance.
Nematodes
These are soil-inhabiting worms that are parasitic on plants and animals.
They have been most most effective against beetle and moth borer larvae.
Bacteria
These are single-celled organisms and the oldest commercially marketed
biological insecticides. Bacteria must be ingested in order to cause
toxicological effects on the pest. Most pathogenic bacteria contain
a crystalline sport and toxin. When the spore enters the pest's digestive
enzymes to eat holes in its gut, thereby releasing the bacteria and
gut contents into the blood. These events lead to an infection that
eventually kills the pest.
Fungi
These are multi-cellular organisms closely related to plants that
cause diseases in a variety of pests. They infect the pest through
spores that require moisture and humidity in order to germinate and
penetrate
the outer skeleton of the pest. Infected pests die from toxins produced
by the fungus.
Viruses
These are incomplete cellular organisms composed of either DNA or
RNA. They are entirely host dependent, relying on the host for their
development and replication. Naturally occurring viruses frequently
control caterpillar and sawfly outbreaks.
Overview
Biological control methods can be used as part of an overall integrated
pest management (IPM) program to reduce the legal, environmental, and
public safety hazards of chemicals. In addition, it may be a more economical
alternative to some insecticides. Unlike
most insecticides, biological controls are often very specific for
a particular pest. Other helpful insects, animals, or people can go
completely unaffected or disturbed by their use. There is less danger
of impact on the environment and water quality.
