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Did you know that 97% of insects most
commonly seen in our gardens or homes are considered either beneficial or
innocuous? That fact may be a little hard to believe when aphids sometimes
turn crispy green lettuce into something resembling dry sheets of brown
paper. Nonetheless, it is true that nature has provided us with all kinds of
assistance for our horticultural ambitions.
Beneficials come in a remarkable variety of
shapes, sizes and functions. Using function as the determining criterion, they
can be divided into four basic types: predators, parasitoids,
decomposers / recyclers and pollinators.
I. Predators:
Predators are insects and other beneficials that hunt for a living. They catch,
kill and eat other insects. In general, predators are free-living and as large
as or larger than their prey. Predators are typically general feeders: they
consume several or numerous prey over the course of their lives and they may
feed on a wide variety of prey.
Some types of predators,
such as hover or syrphid flies, are predatory only as immatures or larvae. Hover
fly larvae tend to prey primarily on aphids, mealybugs, scale insects and other
soft-bodied insects. In contrast, adult hover flies feed on the nectar and
pollen from flowers and may serve as pollinators.
Other types of predators start hunting as
soon as they hatch into larvae and continue their predatory role throughout
adulthood. Common examples of this group are lady beetles, some species of
lacewings and ground beetles. Many predators are generalists; they eat a wide
variety of prey, such as assassin bugs and the praying mantis. A few are
specialists and will dine on only one species or on a few closely related
species.
Spiders can also serve a vital role as
predators. Spiders are abundant and widespread and, best of all, a natural
controller of insect populations. Spiders are beneficial predators that reduce
pest populations. They oftentimes play a primary role in biological control of
pests in and around homes, yards, gardens and crops.
Lizards make up one of the most diverse and
successful groups of modern reptiles. Several types of lizards occur and none
are harmful to humans or pets. In fact, these lizards are beneficial, as they
prey on a wide variety of small insects such as crickets, cockroaches, moths,
grubs, beetles, flies and grasshoppers. They do not chew their food but swallow
it whole.
II. Parasitoids:
Parasitoids are another kind of desirable natural pest control. Parasitoids are
different from parasites in several important ways. Most importantly for our
purposes, a parasitoid always kills its host, while a parasite usually weakens
its host but rarely kills it. Rather than changing hosts as some parasites do in
order to complete the life cycle, parasitoids develop on or within a single
host.
In some parasitoid-host systems, the parasitoid is close to the same
size (as a full-grown larva) as its host whereas a parasite is much smaller than its
host. In contrast, other parasitoids are very small in size compared to their
host's size. The adult stage of most parasitoids are small to tiny, such as
members of the braconid wasp family. Braconid wasps do not pose any threat to
humans as they do not sting.
The life cycle of a parasitoid is unusual.
Most of the time, it begins when the adult female lays her eggs in or on the
host. When the eggs hatch, the larvae consume the host gradually, ensuring that
their unsuspecting prey stays alive until the larval parasitoid pupates and
is able to survive without the host. Parasitoids tend to be highly
host-specific. They choose one species as a host or, in some cases, a group of
closely related species on which to raise their young.
III. Pollinators:
In contrast to the aforementioned groups, this group of beneficials
is more widely known and appreciated. Pollinators have long been recognized for
their contributions to mankind’s welfare and comfort.
Without pollinators,
there would not be any apples,
pears, cherries, citrus fruit, coffee, melon, cucumbers, melons, squash or
many other common feeds. Just think how difficult morning would become for many
of us without coffee! It is estimated that pollinators are worth at least 20
billion dollars annually just in the United States.
The best known “flower duster” is, of course,
the honey bee. Some less well-known pollinators, such as hover flies, do double
duty as beneficial insects. As adults, they pollinate flowers and, as larvae,
they prey on aphids and other soft-bodied insects.
Many other insects also accomplish pollination. Wasps are important pollinators
of some plants. Some beetle, midge, and even thrips or ant species play a vital
role in pollination of certain flowers. Some butterfly species also pollinate to
a small degree. Various moths are important pollinators for some wildflowers and
various commercial crops such as tobacco.
In today’s world, many pollinators’ existence is threatened. Crops are
decreasing production because of the shortage of pollinators. We have ignored
their value and indiscriminately annihilated them with habitat destruction,
chemicals, and other carelessness. So please take the time to understand their
benefits. Work to keep them healthy.
IV.
Decomposers /Recyclers:
Without the lowly held and underappreciated members of decomposer/recycler group, we would be quite literally over our heads
in dead bodies and organic wastes. A decomposer’s job begins when
some other organism’s life ends. Within that dead organism’s body, essential
nutrients are tightly locked into various chemical compounds.
Decomposers break down the more complicated
compounds into a simpler form usable to themselves and to other life forms. Carbon, nitrogen and other raw
elements that are absolutely essential to all life are released back into the
air, water and soil through the waste products of this group.
The humble earthworm is a decomposer deluxe.
Five hundred thousand earthworms in one acre of soil can produce as much as 50
tons of fertilizer and create drainage equivalent to 2,000 feet of 6 inch
drainage pipe. And these are just the side effects of processing enormous
amounts of plant litter! Other decomposers are the larval stages of love bugs
and crane flies as well as springtails, certain nematodes, bacteria, protozoa
and fungi.
Summary:
Mother Nature has been generous indeed. She seems to have provided us
with antidotes for most of the gardening dilemmas we have.
Now all we have to do is to learn to use them
wisely! We hope that the information provided within this Beneficials in the
Garden web page will help toward that end. We also hope to provide assistance
with recognizing and identifying the array of beneficials likely to be found in
your home garden and landscape!
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