The War Against Weeds

U.S. farmers and gardeners are better armed than ever before for this year's battles against their prime enemies--insects and weeds. Against insects, the wonder insecticide DDT is scheduled for large-scale Government tests and a limited amount will be available for civilian experiments this year. Against weeds, the No. 1 enemy, which cost farmers as much ($3,000,000,000) as all other pests combined, the prospects are even brighter. Some promising weapons: P: A flamethrower. Used mainly on cotton, sugar cane and corn plantations, this tractor-drawn implement spurts a 2,200DEG flame along the ground between rows, burns off weeds without harming the stouter stalks of crop plants, costs only one-tenth as much as hoeing. P: Calcium cyanamide. This chemical, long used as fertilizer, has recently proved a potent weed destroyer when applied to the soil in extra-heavy doses before planting. Chief users so far: tobacco growers. P:Oil. California vegetable growers who have tried spraying the soil with a light oil report it highly effective against weeds in carrot and onion fields. P: Borax. In heavy applications, this chemical sterilizes the soil against weeds for two years, has given promising results on railway roadbeds and highway shoulders. P: Ammonium sulfamate. This new chemical, recently put on the market by Du Pont, has been so successful against poison ivy that enthusiasts predict the complete eradication of that noxious weed from the U.S.

2-4-D. Last week news of a sensational new weed killer which may eclipse all these was spreading rapidly among U.S. farmers and suburbanites. It is a synthetic hormone, called 2-4-D* by the U.S. Department of Agriculture, which helped develop it. A very dilute dose (one pound of the chemical to 75 gallons of water), when sprayed on the leaves, kills the toughest U.S. weed--the perennial wild morning glory (also called bindweed). It is also deadly to poison ivy, poison oak, sumac, horse nettle, chickweed, thistles, plaintain, dandelions, ragweed. But it is harmless to animals, is not inflammable, does not corrode sprayers or reduce the fertility of the soil.

Plant hormones have long been used for such beneficent purposes as preventing the premature fall of apples from trees. The discoverer of their lethal possibilities is an Ambler, Pa. chemist named Franklin D. Jones. Because his children are unusually susceptible to poison ivy, Mr. Jones two years ago set out to find an ivy eradicator. He tried nine types of hormone sprays. Some only made the ivy grow more luxuriantly. But in the autumn he noticed that plants which he had sprayed with 2-4-D (and a closely related hormone known as TCP) took on autumn colors unusually early, then withered and died. Cheap Killer. Jones and agricultural experimenters have now developed quicker-acting doses. As a commercial preparation (trade name: Weedone), the chemical is a relatively cheap weed killer ($10 to $15 per acre). It takes ten days to six weeks to kill a weed. But it is thorough, completely destroying the deepest-rooted plant. No one knows exactly how it works. The hormone, absorbed by the leaves, spreads to the roots and somehow, perhaps by breaking down or paralyzing the cells, destroys the plant's chlorophyll. It is not a kill-all; quackgrass, for example, seems to be immune to it. But its selectiveness is its most valuable quality: applied in the right doses and at the right time, 2-4-D seems to be capable of killing most weeds without injuring lawn grass (exception: bent grass), pastures or grain.

-Full name: 2-4-dichlorophenoxyacetic acid.

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