INSECT PESTS.

Manawatu Herald, Volume XLIII, Issue 2232, 29 January 1921, Page 4

INSECT PESTS.

LECTURE BY DR. R. J. » TILYARD.

There was a large and representative audience of scientists and laymen at the Municipal Hall at Palmerston on Wednesday evening, to listen to an illustrated lecture by Dr. R. J. Tilyard on “The Scientific •Control of Insect Pests.” . Dr. Tilyard, who is head of the biological section of the Cawthron Institute, and the world’s most eminent authority on dragon flies, has that rare faculty of making a purely scientific subject not only intelligible but also intensely interesting to his hearers, and he invested this, which would at first sight appear a “dry-as-dust” topic, with real charm. The Hon. G. M. Thomson, M.L.C., was chairman.

The work of economic entomologists, said the lecturer, should be regarded as on the same plane as other branches of scientific investigation, and their efforts in the direction of saving the world’s food supply were of the utmost, importance. Insects took toll of from 15 to 20 per cent, of the world’s vegetable foods, and if the entomologist, could save one half or a cjuaitei of that percentage the study was deserving of the support of the whole world. The Americans were the leaders in this science, and the. speaker paid a warm tribute to the results they had already achieved. At Honolulu, for example, the sugar planters in 25 years had spent two million dollars on an experimental station, and at the present time the saving to Hawaii was assessed at seven million dollars annually. Entomology was a good investment, as they would find if they encouraged its study in New Zealand. Prevenlicm was better than cure, and the quarantining and fumigation of fruit was an important, indeed essential precaulion, for this country, which was now most lightly attacked by insect pests, but for every species that had managed to get into the country there were twenty nwaiting the opportunity. Hydrocyanic acid gas and carbon bisulphide had been proved most effective fumigating agents. The second method for the destruction of pests was by spraying. An intense study had been made of this method in the U.S.A., and their methods had reached a very high state of perfec - tion. It had been largely employed in controlling the little insects which if allowed to flourish would eventually defoliate whole forests. In this connection the strength of the solution did not apepar to be of such importance as the force with which the spray was ejected. A further me)hod of eradicating parasites, but less frequently employed, was that of’ inoculation or injection of chemicals into the trees in the early spring when the sap was rising. Copper and ferrous sulphate solutions had been so employed with sticccs.-. The number of quack substances which had been put on (he market had, however, caused this method to fall into disrepute, but lie believed that the Italian Government had discovered, and was carefully guarding, a new and valuable method of inoculation. The speaker hoped that in the course of a few years cheaper and more efficacious means of injection \yould be used. Mcndelism also was associated with the fortifying of certain varieties of trees by grafting it more impervious ■species with them, and in many cases, notably in the vineyards of Europe and Australia, complete immunity from particular pests had been obtained. This immunity of certain stocks seemed to point io a subtle difference in the constitution of the saps—that quality they hoped one day to discover. Another and most important way of controlling' blights, etc,, was by letting the insects’ natural enemies deal with them. These valuable insects could be divided into classes predatory and parasitical. The former killed and devoured their prey, the latter fed on the eggs or the living tissue of the animal itself. Both varieties however, suffered from a grave disability—each in turn was preyed upon by parasites of its own. 1 hi.> wav of dealing with the pests was to his mind the cheapest and most successful.

The lecture was profusely illustrated by excellent slides, which assisted tiie lecturer and audience materially in getting on common ground. Dr. Tilyard was warmh thanked for his interesting and valuable address by acclamation.