DDT-Proofed

One trouble with DDT is that insects get used to it, develop hardy strains that resist the poison. Another trouble is that DDT kills both injurious insects and their natural enemies. In some cases, long-continued spraying with DDT has caused insect plagues by killing "good" bugs (e.g., insects' parasites) and leaving the bad bugs alive.

Last week Dr. Patrick D. Pielou of the Dominion Parasite Laboratory at Belleville, Ont. told how he hopes to lick this problem. Dr. Pielou breeds friendly bugs called Macrocentrus (which attack the destructive Oriental fruit moth) and exposes each generation of them to DDT not quite strong enough to wipe them out. The survivors, says Dr. Pielou, grow progressively tougher. Eventually, he hopes, they will be able to ignore DDT. Then they will be released in orchards to mop up the fruit moths that have survived DDT-ing.

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