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Of course, not all
members of the insect family are pests of plants. Some
of them are predators and parasites of other insect
species. These can be the gardener's friends and go by
the name of beneficial insects.
 In nature, everything
eventually comes into a balance unless some outside
factor interferes. For every insect that eats on plants,
there are other living organisms that feed on them.
Beneficial insects have
many positives for the home landscape gardener. First of
all, they can do that job that many people rely on
pesticides to do. This can helps save money and prevent
contamination of the environment with sprays. Once
established, they do not have to be reapplied like
pesticides.
Of course, there are also
some difficulties associated with relying on beneficial
insects to control your pests. As with any "organic"
approach, they will not totally eliminate the pests.
They will eventually form a relationship with their prey
so that when pest numbers are high, beneficial insect
numbers will rise to meet the challenge. However, they
cannot eat them all or the beneficial insect would be
out of business too. So, there are always at least some
of the pests around resulting in some damage to the
landscape plants.
Also, if you are going to
depend on beneficials, you have to go all the way.
Spraying pesticides for other problems on your property
(or maybe even on adjacent properties) may kill off the
beneficial insects along with the targeted pests. |
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PREDATORY INSECTS |
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Just like in the larger
animal kingdom, predator insects make their living by
killing and eating other insects. They are usually
larger than their prey and do them in by chewing them up
or sucking the juices out of their bodies. To develop
fully, predators need a lot of food so they need large
populations of their prey (i.e. plant pests) to survive
and multiply. |
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Syrphid Fly Larvae
- These insects are related to bee flies or hover
flies. They are brightly covered with yellow and
black stripes that look like yellow jackets. The
larvae feed on
aphids,
scale and small
caterpillars
and can keep low populations in line.
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Cecidomylid Larvae
- Members of this fly family are predators of
aphids,
scales,
thrips and
spider
mites. The adults
are nocturnal and are not often seen. Larvae kill
their prey by sucking out the body fluids. They go
through about six generations per growing season.
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Ladybird
or Ladybug Beetles
- These members of the Coccineilladae Family are
good predators of
aphids,
scales,
whiteflies and
spider mites. About 400 species are native to
North
America and they are voracious eaters. More on
Ladybugs...
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Lacewings
- Known for its lacy, net veined wings, this member
of the Chrysopidae Family is a predator of
aphids,
mealybugs,
leafhoppers,
thripss, scales, spider mites
and the eggs of moths. As the larvae develop, their
sticky bodies accumulate dead bodies and debris from
their environment which give them a strange
appearance. There are two generations per year.
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Predaceous Bugs - Some of the group of
insects called "true bugs" such as the tarnished
plant bug are plant pests. However, there are
several others in the group that are predators.
These good guys fall into two categories. The
assassin bugs are large, brown or black bugs. They
eat
aphids,
leafhoppers, scale and caterpillars. The
second group called damsel bugs have the same menu
of insects. Both types will also feed on other
predators such as ladybird beetle larvae.
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Predaceous Mites - These creatures feed
on others of their kind, i.e.
spider mites. If the
population of the prey increases, these predaceous
mites can reproduce rapidly to respond.
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PARASITIC INSECTS |
These are mostly
species of wasps and flies that are smaller than the
prey insects that they live on. Adults lay their
eggs either on or in the victim. The larva feed on
the juices and organs of the host. Unlike other
parasites who do not kill their hosts, parasitic
insects generally continue to eat until their host
is dead.
The group of
parasitic insects would include:
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Tachinidae
Flies - There are over 1,300 species of
this type of fly in North America. Most of them are
parasitic insects that feed on caterpillars and the
larvae of beetles. They tend to be medium to large
as adults with dull coloring and prominent bristles.
Unlike most other insects, this group of flies
generally do not lay eggs. Instead, the inject fully
develop tiny instar larvae directly in or onto the
host insect. When they are done feeding, only the
"skin" of the host is left. They attack several
different species of hosts.
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Ichneumon Wasps - These slender bodied
wasps have long antennae and permanently extended
ovipositor (rear end egg depositer) which may be as
long as the wasp's body. This is a very large size
group of wasps that vary quite a lot. Generally,
they are either internal or external parasites
caterpillars, beetle larvae and sawflies.
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Braconid Wasps - This is another group of
parasitic, non-stinging wasps similar to the
Ichneumon wasps but smaller. Their hosts include
caterpillars, beetles (larvae and adults), maggots,
sawflies and
aphids.
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Egg
Parasites - Many of the tiny wasps also
attack the eggs of members of the Family Lepidoptera
which includes most caterpillars that turn in to
butterflies and moths. They spend the winter inside
the eggs of the host species.
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Note: We
have provided some general information and
observations on this topic aimed at the home
gardener. Before you take
any serious action in your landscape, check
with your state's land grant university's
Cooperative
Extension
Service for the most current,
appropriate, localized recommendations. |
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