Overcoming Resistance To D.D.T.

Press, Volume CIII, Issue 30585, 30 October 1964, Page 1

Overcoming Resistance To D.D.T.

An additive to D.D.T., intended to make the insecticide once more effective against insect strains which have become resistant to it, is under test at Lincoln College, where Dr. R. A. Harrison. senior lecturer in charge of the department of agricultural zoology, is using it against captive D.D.T.-resistant houseflies.

The additive has been developed by an overseas manufacturer, and is being tested under laboratory conditions by several entomologists in various parts of the world. Success against house flies would almost certainly involve success also against other D.D.T.-resistant insects such as mosquitoes, grassgrubs, leaf-rollers, and others suspected of having developed resistance such as cod-[ lin moth and porina moth (subterranean caterpillar). D.D.T.-resistant house flies; and other insects are able to! survive treatment by very large amounts of D.D.T. I

through the manufacture in the insect’s body of an enzyme able to destroy the insecticide. The new material acts by inhibiting the action of the - enzyme and thus allowing the D.D.T. to do its work.

The tests being carried out by Dr. Harrison take a long time, even though house-flies can go through a complete generation in about a fortnight. The maximum amount of information can be gained from the tests only if the flies are all of about the same age, and if a large number of t flies is available at one time I for the test; to get these conditions, the populations must i be allowed to build up to high .levels after each application | of insecticide. Last summer, ! Dr. Harrison could only apply jthe insecticide twice. The kills of resistant flies are ! checked against the kill of a 'non-resistant line supplied to Dr. Harrison from Italy on behalf of the World Health Organisation. So far, Dr. Harrison says, the kill of resistant flies by the D.D.T. with the new addiItive has proved highly satisfactory, without any apparent tendency for resistance to reappear; but it is too early, yet, for any permanent success to be claimed. The World Health Organisa-

'tion has given a fellowship to 1 Dr. K. Yasutomi, of the Japan- i ese National Institute of ; Health, Tokyo, to come to New s

Zealand for six or seven months from the end of next year to work with Dr. Harrison.