Deadlier Insecticide

Ever since DDT came out of the laboratory two years ago, chemists have been trying to improve on the "wonder killer." Last week a Britisher announced his entry: "Activated DDT," a concoction of pyrethrum and DDT.*

The inventor, Cambridge Chemist Harry Hurst, 34, claimed that he had got rid of the defects in DDT (see below). DDT is 1) slow, and 2) deadly to good as well as bad insects. Dr. Hurst said that some of his mixtures seem to be highly selective, attacking pests but leaving useful insects unharmed. He had also found Activated DDT lethal to some bothersome insects, notably cockroaches, which are not bothered much by DDT alone.

To demonstrate the speed of his killer, Dr. Hurst released 1,000 houseflies in a room 15 by 15 ft., noted the wall spaces where most of them alighted, then painted the spots with his preparation. In 27 minutes every fly was dead.

Other demonstrations have been equally impressive.

Since last summer, flies have had no truck with 240 shops of the big British chain, Marks and Spencer; Dr. Hurst's spot-painting did the trick (one store which he treated only once, on August 22, 1945, has not had a fly since).

Several badly infested London hospitals have been completely cleared of cockroaches; a Hurst emulsion not only killed all adult roaches at once but persisted long enough to destroy young ones as they hatched.

A Marseilles businessman, Emille Bouche, sprayed a 20-acre orchard infested with cockchafers, killed them all in 21 minutes. Honey bees (normally vulnerable to DDT) seemed undamaged. To find out whether Activated DDT was toxic to animals, Bouche fed 400 hens for two weeks on an exclusive diet of poisoned cockchafers. The hens thrived. Bouche, much impressed, promptly invested his all in building seven French factories for manufacturing Activated DDT.

U.S. entomologists last week made a preliminary report on another sensational British insect killer, Gammexane, claimed to be five times as deadly as DDT (TIME, May 28, 1945). It has an unpleasant naphthalene smell, lacks DDT's lasting effect. It is particularly potent against cockroaches, proved effective in checking a locust plague in Sardinia this spring, and has shown promise against the cotton boll weevil. But in the sunny U.S. climate it has been generally less lethal than in foggy Britain.

* A mixture of quick "knockdown" pyrethrum and DDT has been used in many preparations, notably the U.S. Army's "aerosol" insect bombs, now being sold to U.S. householders. But Activated DDT is supposed to penetrate an insect's chitin (outer skin) and reach its nervous system more surely than previous mixtures.

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