Man versus Insect

Sun (Auckland), Volume III, Issue 673, 27 May 1929, Page 8

Man versus Insect

Pests Threaten World Food Supply

MAN’S fight against liis enemy the insect has become a struggle for existence. Scientists cannot yet determine who will win. New Zealand, along with other countries, is experimenting' feverishly with parasites, in which man sees his strongest hope for ultimate victory.

TRILLIONS of money have been

saved to New Zealand in recent years by the work of the Cawthron Institute at Nelson in fighting insect pests. Something like £400,000 a year is saved the sheep-raising industry alone by the successful parasitisation of the common blowfly, and other enemies of animal and plant growth have been forcibly driven back.

But the rapid spread of insects throughout the world 'has assumed more than a mere money-saving job. It has become a struggle for existence; the survival of the fittest. Man or insect must win. There is not food on earth for both of them.

In some countries crops are threatened by complete extinction and orchardists are facing ruin. The earth is inhabited by about 120,000 species of beetle, and by winged pests, including flies, numbering many more than that—altogether about a quarter of a million kinds of insects for man to fight in his efforts to retain for human consumption the food of the world. MAN’S FOOD ATTACKED “Will the insects starve us?” asked an eminent American scientist when recording that million" of money have been poured into tbe battle against borers, moths and beetles-—in some cases with little result—and complaining that through insects and plant diseases we are now losing 10 per cent, of all food raised. Parasitic recruits from overseas are carefully transported to New Zealand at intervals to help in the campaign. Fruit and flowers; vegetables and grain crops suffer the ravages of insects which originally ■were imported in more or less strange circumstances. The “lady-bird” beetle has been used extensively and successfully in clearing fruit trees of blight and other visitations, and some of these tiny beetles were sent from Australia to California to help in clearing out the fluted scale from the fruit crops there. Insects migrate from country to

country in unexpected ways. Foreign timber is reputed to be responsible for the arrival in New Zealand of several species of pests. Bunches of fibrous matter, too, often harbour these stowaways. America and Continental countries are leading the world in this research, but New Zealand is coming in annually for a great share in the crusade. The elimination of one problem brings with it the hirth of another, and science i 3 ever busy in its battle with this living pest.

Fate has played its part in the spread of pests. A gust of wind which blew round tbe corner of a house in an American town in the late ’sixties of last, century upset the efforts of a French scientist named Trouvelot, who was experimenting with the brown moth and the moth of the silkworm. A box was overturned and the eggs scattered. For ten years nothing happened. Then a swarm of caterpillars began to over-run the country. They left trees standing bare mile after mile, and started off the plague of the gypsy moth. Now, after many years fighting, the moths are reputed to be more numerous than ever before. VORACIOUS MOTHS

So voracious are the caterpillars of the gypsy moth that a man with a similar appetite would require two or three tons of food a day! Corn borers, too, have given scientists many hours of anxious thought, but the Ichneumon fly, an effective parasite, has been found to be unerring .in its search for the borer. This fly lays its egg through the tough layer of the corn stalk, and in every case marks accurately the spot opposite the busy borer. Presumably it listens to the borer at work; then instinctive judgment does the rest.

Delicate instruments, by which the grain insects may be heard working deep in a stored heap of grain, have been brought to the aid of man, but hordes of insect pests are still sweeping his domain. All the resources of science and all man's ingenuity will be required if victory is to be won in this fight for possession of the earth. As an Auckland scientist said the other day; “So fierce is this battle beween insect and man that it is difficult to say yet which of the two groups will in the end become dominant.”