Insect Enemies and their Control

[music] This is an entomologist, a person who specializes in the study of insects. Many of the thousands of kinds of insects these scientists study are helpful to mankind. Fruit flies, for example, are useful in studies of heredity. Bees and other insects are helpful in pollinating flowers. Some insects act as scavengers, eating bits of dead animal and plant matter. However, there is a small but very important segment of the total insect population that destroys our crops, endangers our health, the health of our domestic animals and damages our homes. By understanding the habits of insects, their life cycles, their structures, and their physiology, entomologists are able to carry on a more effective battle against the enormous damage that harmful insects cause us. Entomologists are often called upon to identify insect specimens found in plants. Quarantine inspectors, some of whom are entomologists, prevent infested plants from coming into the country. Corn, for example, is a crop that is attacked by an insect pest accidentally brought into the United States. The European corn borer. The cornbore moth lays eggs on the unders sides of corn leaves in June. These hatch into destructive larve, which in turn are followed by a second generation of moths and larve in early August. The second brood larve eat and destroy the stalks and ears. To combat this pest, some farmers delay their date of planting. This results in the corn being small and having little food value for the first generation larve when they are ready to hatch. Planting insectresistant varieties of corn also reduces crop damage. One of the common measures of control against the European cornb is the application of chemical insecticides. Control measures against insect pests are absolutely necessary for the production of our fruit crops. One insect which does damage to the apple crop is the coddling moth. The coddling moths lay their eggs on the leaves and twigs of apple trees in the spring. The larve feed briefly on the leaves and then eat their way into the apples. After feeding on the seeds within the cores, the larve leave the apples and find a sheltered place to spin their cocoons. These cocoons are on a discarded wooden box. The larve in the cocoons can be destroyed by burning such containers and other debris that accumulate in apple orchards. Frequent spraying of apple trees with insecticides during the growing season also helps prevent damage from the coddling moth. Each year, cotton crops are damaged by the larve of the bullw weevil. The adult weevil's long snout is used to bore an opening in the bowl which contains the developing cotton. The insect lays eggs in the hole it makes and the larve which hatch begin to eat inside the bowl. The result of this destruction is no cotton or at best short discolored fiber which has little commercial value. Dusting cotton fields from the air with insecticides is an effective method of protection from the bullw weevil. There are many kinds of insecticides needed to control insects. Some will kill chewing insects such as grasshoppers while others will destroy sucking insects such as aphids. Aphids and other insects are also eaten by birds. Birds are an important natural control of insects and so conserving our bird life is another way of controlling harmful insects. Some insects are killed by other insects. This parasitic wasp is depositing her eggs in a caterpillar. The larve get their nourishment from the body of the insect host. Then the larve spin cocoons which we see on the skin of this caterpillar. Eventually the infested insect dies. Orange trees and other citrus fruits are sometimes injured by the cottony cushion scale. A small sucking insect which feeds on the trees and fruit. Lady beatles are a natural enemy of the cottony cushion scale and they are sometimes placed in groves. The lady beetles destroy the scale. But insects do damage other than to our crops. Some insects, such as the common housefly, are dangerous to our health. Flies carry disease germs on the hairy portions of their legs. House flies feed on decaying matter in which they also lay their eggs. The eggs in turn hatch into larve called maggots. By wrapping garbage and by sealing containers, we can prevent adult flies from reaching wastess where they may lay their eggs. Screens will protect our homes against flies, mosquitoes, and other insect pests, too. Mosquitoes are blood sucking insects. The Cullex and Aedes mosquitoes are mainly a nuisance, biting their victims and causing minor irritation. But some mosquitoes are serious threats to health. The anophles mosquito, for example, carries the microorganism causing malaria. Mosquito larve live in water and breathe through tubes which penetrate the surface of the water. To destroy these larve, safe insecticides are used which form a film on the water. The chemical film kills the larve by contact with them. Considerable damage is done in our households every year by another insect, the common clothes moth. Damage is not done by the adult moth, but by the larve, which feed on woolen fabric. Garments can be protected against closed moths by dry cleaning and by using paradicchlorobenzene crystals. The vapors from these crystals keep away the adult moths that lay the eggs. Termites are insect pests which also infest homes in a different way. They may be found in the ground or in wooden structures of buildings. The food of termites is wood or cellulose in some form and within their intestines are microscopic protozoa which digest the cellulose. Treating the soil around foundations of buildings with a long-asting chemical is the preferred method of preventing termite damage. The chemical forms a toxic barrier which termites cannot penetrate. This was once a beautiful elm tree. We can see what caused its destruction by peeling off the dead bark. Here we see the pattern of marks made by the burrowing of the European elm bark beetles which carry the Dutch elm disease fungus. Infected trees are removed and burned in order to destroy breeding places of these insects and prevent Dutch elm disease from spreading to healthy trees. The war against all insect pests is a neverending struggle. Methods are being continually applied to combat insects that destroy food crops. Insects that affect our health and insects that cause damage to our property. All of us benefit from the many different control methods which are used in the continuing fight against harmful insects. [music] >> [music]