Science: DDT

(2 of 2)

DDT owes its deadliness partly to an almost unique property: on insects it acts as both a contact and stomach poison. It first paralyzes an insect's hind legs, then gives it a violent attack of the jitters, finally brings on complete paralysis and death. Oddly, the pure chemical has little effect; it is good only in an oil solution or when mixed with inert powder. The usual dose is 1% to 5% DDT, dissolved in kerosene or mixed with a dust filler.

But DDT is not a kill-all. Against two of the most common U.S. crop destroyers, the Mexican bean beetle and the cotton boll weevil, DDT has proved disappointing. Man has not yet won his war with the insects.