Du Pont v. Pests

"In nature," explained Dr. Wendell Holmes Tisdale, "there is no such thing as a pest. But in human economy, anything that competes with man for his means of subsistence may be considered a pest."

Dr. Tisdale, a big, florid Alabaman of 45, is director of Du Font's new anti-pest laboratory which was formally opened last week in the suburbs of Wilmington, and of which the formal name is Pest Control Research Section, Grasselli Chemicals Department, E. I. du Pont de Nemours & Co. A handful of newshawks assembled in the gleaming Nemours building, lunched with Lammot du Pont, who shook each one's hand, spent the afternoon in the battleship-grey laboratory, wound up at the Hotel du Pont bar.

Du Pont has manufactured insecticides (Bordeaux Mixture, Calcium Arsenate, Dutox, Spreader & Sticker, Lime Sulphur Solution) since 1929. Its new laboratory is devoted to war on all sorts of pests-- insects, fungi, worms, bacteria, weeds, rodents, marine plants, marine animals-- and claims therefore to be unique. On its staff are two plant pathologists, six entomologists, four chemists, some 20 assistants. With an initial investment of $100,000, the laboratory's operating cost is expected to be $125,000 a year. Object is to find new and better insecticides which Du Pont can sell to farmers, nurserymen, fishermen, manufacturers, housewives.

A most important division in the anti-pest laboratory is that of Moths & Flies. From outsiders with anti-moth ideas it is already being flooded with more telephone calls and mail than its staff members have time to answer. Most commercial moth repellents are fluorine compounds or cinchona alkaloids of the quinine family. At the Du Pont laboratory, experiments have been carried on with these and scores of other chemicals. What they hope to find eventually is a moth-killer which will impregnate a fabric like dye, will not be removed by washing or dry-cleaning. Moths eat almost any animal tissue--wool, silk, feathers, even leather and deer antlers. They will not, however, eat wool if it is completely sterile. Presumably impurities in the air and traces of perspiration provide spice enough under ordinary conditions.

Du Pont flies are fed milk and bread. Their eggs are hatched in a "synthetic manure" of wheat bran, alfalfa meal, yeast and malt. Codling moths, scourge of apple growers, have a room to themselves, with long rows of little green apples, each hanging from its own hook. These insects are caught by nailing corrugated paper board to apple trees. The moth larvae think this material is bark, dig in. Their cages are hung with purple cellophane to simulate twilight. In the greenhouse basement is the Japanese beetle division. This handsome insect, whose U. S. infestation is spreading from a focus in New Jersey, is prone to go on hunger-strikes in captivity, avoid the sprayed plants which the researchers want them to eat. The strike is broken by shining a powerful light in their cages, which attracts them upward from the floor. They cannot cling to the glass walls and tops of the cages, so are forced to settle on the plants. Once there they give up and start eating.

All the intermediate and by-product chemicals (more than 2,500) evolved in the Du Pont company's manifold processes are at the disposal of the pest laboratory for experiment. Tetra-methyl-thiuram-disulphide, an intermediate which occurs in the manufacture of rubber accelerators, was found to be a fine weapon against the Japanese beetle. A similar compound, phenothyiazine, turned out to be a stomach poison for codling moths. New substances like these are useful replacements for insecticides which were once effective but are so no longer--because of the queer immunities which some insects acquire. The Colorado codling moth now survives doses of lead arsenate which used to kill it. The red-scale citrus insects, which prey on Texas and California orchards, first toughened themselves to oil emulsions and then to hydrocyanic gas, are now hard to kill even with a combination of the two.

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