Science: Mithridates, He Died Old

Does DDT upset the balance of nature? Yes, but that’s nothing to be alarmed about, says one of Britain’s foremost authorities on insect physiology. The authority, who has the nervous name of Dr. Vincent Brian Wigglesworth, writing in the December Atlantic Monthly, took the long, calm view: chemicals have upset nature’s balance before and DDT is merely the latest and most violent. The laws of nature have never been abrogated and there is no reason to believe that DDT can do it. Points and examples:

¶ Odd things happen in fruit orchards from indiscriminate use of DDT. The woolly aphis is not bothered much by DDT, while the Aphelinus parasite, which normally discourages woolly aphis, is wiped out entirely. In orchards where the red spider has been kept under control by its enemies, “trees have been literally scarlet with red spiders after being sprayed with DDT.”

¶ High concentrations of DDT used against forest pests kill fish indirectly, by killing aquatic insects. Crayfish and tadpoles, both important fish foods, can be killed by contact with DDT and by eating DDT-contaminated food.

¶ DDT can kill bees if they are confined in cages which contain plants sprayed with DDT. But that is no news to beekeepers, who have always had trouble with arsenic sprays. Dr. Wigglesworth steps delicately around the whole bee problem with an observation: “. . . beekeepers are a vociferous race. Like the bees they care for, their more lovable qualities may become obscure when they are roused—and they do not take kindly to DDT.”

Insecticides, says Dr. Wigglesworth, are subject to the law of diminishing returns. Over the years more & more chemicals are needed to do the same job. Two arsenical washes once controlled the coding moth on apple trees; now five to seven are needed in the same orchards. Four years ago tartar emetic was hailed as the new and perfect control for citrus thrips in California. Within two years a more hardy variety of thrips appeared and tartar emetic ceased to work. Dr. Wigglesworth suspects that even powerful DDT may begin to need some extra strength one of these days.

The January FORTUNE also gave DDT a careful, steady look. Its findings were in general agreement with Dr. Wigglesworth’s. A few warnings and suggestions:

¶ A residue of DDT on general crops may have a bad effect on the nervous systems of both humans and farm animals. DDT is still regarded as too tricky for use on general crops.

¶ DDT is definitely poisonous to certain plants, e.g., squash, cucumbers and melons are killed or stunted by small doses. Tomatoes, corn, beans and rye are sometimes retarded.

¶ Housewives can battle most insects effectively and safely with 5% concentrations of DDT in kerosene sprays or water suspensions.