Insect Control (1973)

I the earth is filled with many forms of animal life of all these forms the insects are the most numerous insects by their pollinating activities make possible the growth of an orange tree a rose a pea clover and cotton they provide us with honey beeswax and silk they are food for many kinds of birds and fish the world could not exist in its present form without them while insects are necessary and valuable in maintaining the natural world as we know it certain insects are harmful to man they attack the food crop he is planted and the forest he wishes to grow they carry him spread disease endangering man's health and a health of his domestic animals when this happens the insect becomes a pest but threat to man you for many thousands of years man's only defense against the pest insect was hand picking it from the plant or making attempts to drive it away for hundreds of years ignorance permitted deadly epidemics of insect-borne diseases to ravage human populations but his time passed man's knowledge of the lifecycle of insects increased he was sometimes able to time his planting or harvesting to avoid a pest by discovering their breeding places he was able to destroy them but more effective and reliable controls were needed during World War 2 the chemical compound DDT was discovered to have the capability of killing insects it revolutionized man's ability to control pests DDT prevented typhus epidemics in Europe and was used extensively in the destruction of the malaria carrying mosquitoes in the tropics but DDT was not the final solution to the pest problem with the steady rise since World War two in the application of pesticides to the environment has come the growing realization that they can be dangerous not only to the insect they are meant to destroy but to birds fish and other forms of life including man extensive study of the effects of DDT has alerted us to the dangers of the widespread application of poisonous substances to the environment but the need to control injurious insects remains the question arises how can we prevent pest insects from doing harm to us and at the same time how do we not harm ourselves and those animal species we need one answer is biological control or the development and use of non chemical means to control harmful insects work being done with the gypsy moth illustrates the different approaches to non-chemical insect control now being investigated the gypsy moth is a forest affiliating insect it was first brought to this country in eighteen sixty nine by naturalist to wish to develop a silkworm hardy enough to survive the New England winters the moth escaped from his laboratory and because it had no natural enemies in its new environment soon multiplied and spread causing extensive damage to the forests of the northeastern United States a variety of steps taken to destroy or halt the spread of the moc over the past century have failed the young gypsy moth caterpillar hatches in the late spring it grows rapidly feeding on a great variety of leaves this is the gypsy moths troublesome stage when it actually de folie eights large areas of woodland you in an attempt to halt the destructive insect scientists are now investigating non-chemical means of bringing it into balance with its environment research efforts began in the laboratory gypsy moth eggs are collected in the forest and brought to the laboratory to be reared this beginning is the most critical part of the biological control research program a continuous supply of healthy insects for use in the experiments being conducted is assured one possible way of controlling harmful insects is by spreading disease among them entomologists have discovered two microorganisms that are fatal to the gypsy moth a virus and a bacterium when fed to the moth larvae in the laboratory they cause the larvae to die but the laboratories one thing the field quite another to be effective the virus and bacteria must work in the forest scientists set up experimental plots in areas infested with gypsy moths as an example of the problems faced in the forest that researchers knew that even the best spraying methods could not cover every leaf of every tree because the moth larva could not be controlled unless they ate the virus or bacterium entomologist designed a feeding preference experiment to discover if the insect could sense the presence of the sprayed material on the leaf the results of the experiment would be used as a guide in preparing the spray to be used in the forest the scientists also discovered that the virus was destroyed when exposed to the rays of the Sun the material had to be found it would protect the sprayed virus in another experiment researchers mixed the virus with many different liquids and sprayed the mixture in the forest after spraying leaves were collected and taken into the laboratory there they were fed to the laboratory reared insects to see if the mixture was effective in protecting the virus from the sun's rays the most effective mixture would be used in larger sprains while research continues in this type of biological control of harmful insects other approaches are being investigated entomologists now know that many kinds of insects are the natural enemies of other kinds insects do more to keep themselves under control than man could ever do the use of natural insect enemies to control harmful insects is another aspect of biological control a predator insect is one that devours its prey a parasite lays its eggs inside another insect the egg will hatch and the young insect will feed and grow inside its host when it has grown it will emerge killing the host insect to find out what parasites present in the forest will attack the gypsy moth cages containing gypsy moth pupae the last growth stage before the insect becomes an adult are placed in the forest by using this method entomologists found that this small wasp like insect was a parasite of the gypsy moth pupae research has indicated that it may in sufficient numbers be used in the control of the moth researchers continue to search the forest for more parasites and predators of the gypsy moth they continue laboratory experiments to better understand the relationship between a parasite and the insect it will lay its eggs in another approach non-chemical control of harmful insects is the idea that they may somehow be kept from reproducing the female gypsy moth is a poor flier weighted down by the unfertilized egg she carries she tends to stay in one place to attract the male she sends out a powerful odor the male finds her and fertilizes the eggs scientists have learned how to manufacture the sex attractant of the moth they have placed the attractant entraps to find out if they are able to catch the mail before he finds the female Forest entomologists also think that large amounts of the attractant sprayed by plane over a forest may confuse the male moth to such a point that he will be unable to find a female it may work in two ways by spraying a large amount of the attractant over an area thus creating many attractive points the male may be unable to pinpoint where the female is or by having to fly from point to point in his search he may simply be worn out and stop searching prior to spraying researchers place male and female moths who are ready to mate in the forest after spraying they locate the female and bring her and the egg she has laid back to the laboratory they will then determine if the eggs have been fertilized and can judge the effectiveness of the sex attractant as a means of control before we know whether or not any of these non chemical control techniques will work against pest insects more research is needed but man in turning to biological controls takes his lesson from the natural world by observing seeking to understand and utilizing its intricate system of checks and balances we may achieve control over injurious insects without harming or destroying the other living creatures who share the earth you