NATURAL ENEMIES.

Otago Witness, Issue 3865, 10 April 1928, Page 12

NATURAL ENEMIES.

. idicct pests of various kinds cause enormous losses throughout the world. They prey upon plants as well as upon animals, and their numbers are as the sands along the seashore. They assume a multitude of forms, and they display amazing adaptation. We have been told that every living thing has a purpose. It is -extremely difficult, however, to understand why mankind should be made the victim, indirectly at any rate, of such a vast array of pests—for our sins maybe. That the existence and activities of the different enemies have been beneficial in many directions is obvious, but it would seem that the benefits have been enormously outweighed by the disadvantages experienced.

There are two means of checking the ravages of insect pests—prevention and remedy. By preventive methods the appearance of the pest is forestalled, and either the surroundings are made too unpleasant to induce it to stay, or the crop is maintained in so vigorous a condition that the insects are unable to effect any permanent injury upon it. Remedial measures usually involve the application to the infested crop of substances which will either kill the insects or drive them away. For a long time, when considering means of coping with the insect pests that afflict the world, attention was devoted almost exclusively to the possibilities of poisonous substances which could'be applied to the objects of attack in such a manner that they would be rendered partially or wholly immune. For instance, in the case of the codlin moth we find entomologists, chemists, and others concerned working together, and they ultimately evolved the system of spraving the trees and fruits with an arsenical preparation to the great benefit of producers and consumers. Again, it was discovered that lice and ticks could be controlled by immersing the animals in certain solutions chemically prepared, and that cut worms could be prevented from destroying cereal crops by distributing poisoned baits. If it be asked why crops are so frequently ravaged by insects, the answer is that in growing vast numbers of the same kind of plant to the exclusion of other plants the cultivator has upset the natural balance of vegetation. Having interfered with the natural growth, it is necessary to safeguard our crops of cereals, fruits, and so on from the raids of the insect hosts, and it is a significant fact that more attention is being given to the discovery and utilisation of natural enemies of the destructive pests of recent years. As a consequence, the economic entomologist is, in a sense, a live wire. It is recognised that the work he is engaged upon has immense possibilities, and that he may ultimately revolutionise the popular attitude toward the problem of insect pest control. In - the course of time, we shall doubtless become familiar with ■ the predacious and parasitic insects. It will take time, though, and while waiting we may-well encourage those of our feathered friends which feed on ■ noxious insects. It is true that these , in some cases'. require payment for their services, and take that, payment in the form of grain, fruit, etc. It is doubtful, however, if the toll taken is more than fair, considering the benefits which they confer. In the United States at present there is a fast growing appreciation of the economic usefulness of different kinds of birds, and special efforts are being put forth to induce the people to encourage the breeding of them . 0 that they the more, effectively perform the work for which nature has designed them. It is interesting in the above connection to note that a move is to be made by the Wanganui River Trust to have the whole of the Wanganui River declared a sanctuary for bird life.’ This is a move in the right direction. It appears that at the present time it is a customary picnic pastime on this river to pot ducks and others of the feathered tribe for the fun of the thing. No use is_made of the birds. It is high time amusement was stopped.. It waspoipted out by the members of the trust -that the bird lifeofthe river was a valuable adjunct lending charm to the general surroundings, and from a tourist point of; view alone it was worth proAt the present finio.'it was ilS carry firearms on to, the trust’s reserves.’-/ . ’’