 |
ENTOMOLOGY AND PEST MANAGEMENT |
|
Entomology is the scientific study of insects. Because they are closely related, we will include spiders, mites and ARTHROPOD pests. Gardeners who understand pest life cycles and behavior are better able to determine when control will be most effective.
You probably have about 1,000 species of insects living in your yard. They are all part of nature's complex ECOSYSTEMS and FOOD CHAINS. Of the nearly 100,000 insect species in the USA, only about 600 species are considered pests. Since few insects are actual pests, Master Gardeners must learn which are pests, which are BENEFICIALS, and which do not affect gardening.
Insects play an integral part in our lives. Many gardeners are aware that beneficial insects are necessary to pollinate many fruit and vegetable crops. Other beneficial insects are the source of honey, beeswax, silk and shellac. Insects also help break down dead plant tissue. Some insects capture and eat other insects and are called predators. Other insects have larvae which attack pests by living inside their bodies and these are called parasitoids.
Pest insects and mites may feed on our plants and our homes, or they may carry diseases that infect plants. A few also carry diseases that infect animals, including people. Master Gardeners use the term "pest management" rather than "pest control" or "pest eradication." We now realize that we cannot eradicate or completely rid our gardens and homes of pests. We can only try to keep pest numbers low to minimize damage.
Pest management is a complex job
that involves much more than just spraying with pesticides.
Master Gardeners must learn how to use other pest management
techniques. You will learn how to use beneficial insects
(BIOLOGICAL CONTROLS). You will also learn how to make homes
and gardens less attractive to pests (CULTURAL
CONTROLS).
KEY CONCEPTS
I. Arthropods
II. Insect Pests of Houses, Pets and Humans
IV. Submitting Insects for Identification
V. Orders of Insects and Their Feeding Parts
Return to Introduction
ARTHROPODS
Insects are a class or subgroup of a larger group called of phylum, known as arthropods (ARE-throw-pods). This word means "jointed foot." The arthropod group includes insects, spiders, crayfish, millipedes and similar animals. The various groups within the arthropods are distinguished from each other by the arrangement of their body parts.
Insects are land animals with 3 pairs of jointed legs. The insect group includes many subgroups: termites; grasshoppers, crickets and roaches; earwigs; lice; true bugs; beetles and grubs; butterflies, moths and caterpillars; fleas; flies, gnats and maggots; and bees and wasps.
The word "insect" comes from a Latin word which means "to cut into." This describes how the bodies of insects are divided into distinct regions: head, thorax and abdomen.
People often refer to insects as bugs. This is incorrect. Bugs are a subgroup of insects, just like the beetles, flies, bees and wasps.
There are three characteristics found among all insects:
3 body regions: head, thorax (THOR-ax) and abdomen (AB-doe-men)
1 pair of antennae (an-TEN-e)
3 pairs of legs attached to the thorax
A typical insect is shown in the following illustration.
None of the arthropods, including insects, have a skeleton of bones. Instead, they have a tough outer shell called an exoskeleton. The exoskeleton provides support and protection. In order to grow, arthropods must shed the exoskeleton or molt.
The insect head contains sensory organs, such as the antennae, eyes and mouth. The antennae on an insect are usually easy to see. One pair is always present on the adult form (except scale insects). Though you may call insect antennae "feelers," they are used by the insect to smell. The antennae can be very helpful in identification. They vary by species in number of segments and shape.
Insect eyes are very different from human eyes. Insect eyes do not form an image like our eyes do. Insect eyes are very good for detecting motion which helps the insect escape danger.
Insects have two basic types of mouthparts: chewing and sucking. There are variations of these two basic types. Thrips have RASPING-sucking mouths. Honeybees, wasps and bumblebees have chewing-lapping mouths. Aphids, scales and mealy bugs, have piercing-sucking mouths. Many of us know firsthand about the blood-sucking mouths of fleas, mosquitoes and lice.
The different mouthpart types cause characteristic types of damage which can be used as clues for identification of the pest. Just as you can identify mammals by their footprints, you can determine the kind of insect causing damage to a plant by the feeding print left by the mouthparts.
The thorax is the middle body region. The legs and wings are attached to this region. Number of wings, the VENATION and the presence of wing covers sometimes will be used in identifying insects. Most adult insects have 2 pairs of wings, though some have lost 1 pair (flies) or even both pairs (fleas). Only adult insects have wings.
The 3 pairs of legs on insects are always present on adults. They may or may not be present on immature stages.
The last body region is the abdomen. It consists of 11 or fewer segments. The number of segments is often helpful in identification.
It is a good idea for the gardener to purchase and use a small magnifying or hand lens. Use it to look for insect eggs and to examine plant damage and very small insects. A hand lens helps with critical distinctions among many common insect pests.
Most gardeners can recognize GRUBS and CATERPILLARS. However, they may not be aware that they are the immature stages of common insects. Insects are very different from other animals. They often progress through very different forms called stages, as they develop into adults.
Understanding insect life cycles is important for management of pests. Many insects are easy to manage during one or two of their stages. Pesticides may not be effective against insect eggs or adults, while the soft immature insect may be easily killed. It, therefore, becomes important to recognize these pests in immature stages of their life cycle.
Metamorphosis (met-a-MORE-feh-sis) is the unique developmental process in insects. Metamorphosis is a combination of two Greek words: "meta" which means change, and "morpho" which means form. Complete or complex metamorphosis has the following stages: egg, larva, pupa and adult. We are probably most familiar with this process in butterflies and moths.
Egg: Insects lay fertilized eggs singly or in clusters. At this stage, vulnerability to chemical control is minimal. The egg has a protective covering. These clusters of eggs often are enclosed in a protective material. However, egg clusters can be removed and crushed. Eggs may be laid in protected, hidden locations to avoid exposure to weather and predators.
Larva: When an egg hatches, the larva emerges. Larvae are the feeding, growing, nonreproductive stage of development. During this stage most insects go through a process called molting. Instead of gradually growing larger, the larva eats until its skin cannot expand any further. The old skin splits and is shed. The stage between each molting is called an instar.
Following each molting stage or instar, feeding increases. In the garden, this can be noticed by increased plant damage. It is during the larval stage that most insects cause plant damage. Caterpillars, grubs and maggots are larval stages of moths and butterflies, beetles and flies, respectively.
Control is usually easiest during the larval stages. The larva is feeding and is more likely to ingest pesticides. During molting, the body is exposed to contact pesticides. Infection by natural diseases and attacks by predators or parasitoids are also more likely.
Pupa: (PEW-pah) is a non-feeding, transforming stage. This stage may form a kind of covering, such as the cocoon or chrysalis made by the butterfly. During this stage the insect transforms into the adult stage, often an entirely different form from the larva. At this stage, the only possible control is mechanical, such as crushing.
Adult: Adults are the reproductive stage of insects. They may or may not feed. Some live for a very brief period, even one day or less. Control is possible during this stage of development, but usually more difficult. It is critical to control pests before they reproduce a new generation.
Many insects do not develop through a complete metamorphosis. Instead they become adults through what is called incomplete or simple metamorphosis. Simple metamorphosis involves a gradual change in size, but not form.
The intermediate stage is called the nymph. Nymphal stages look like the adult, but they may have different color markings and the wings are merely pads visible on the thorax. When the last nymphal instar molts, the newly emerged adult expands the wings. The following illustration shows incomplete metamorphosis.
Many insects overwinter in a dormant state. They can be in any stage of development: egg, larva, pupa or adult. In the garden, insects spend the winter in soil or dead plant material. Rough tilling of the soil can expose the insect to fluctuating temperatures that may kill it. Removal and disposal of plant debris also may eliminate overwintering insect stages.
Certain insects have developed a unique system of living. They live in a social colony. There are different forms within the colony that handle different duties. Each group performs separate duties that ensure survival of the colony. Often, a colony consists of winged reproductives, called queen(s) and drone(s), workers with or without wings, and young that often are completely helpless.
In some social insect groups there is a king, or drone, and soldiers which protect the group. Eggs and immatures are cared for and protected by other colony members. The queen usually has the sole job of laying eggs and establishing a new colony, if necessary. Examples of social insects include ants, termites, wasps, and bees.
Introduction | Botany | Soils and Fertilizers | Entomology and Pest Management | Plant Pathology | Plant Propagation | Houseplants | Lawns | Herbaceous Ornamentals | Woody Ornamentals | Vegetables | Herbs | Fruit | Glossary