Insecticides, Fungicides, and Hormone Sprays Presented before the Division of Agricultural and Food Chemistry at the 102nd Meeting of the American Chemical Society, Atlantic City, N. J. (Pages 489 to 502)
Courtesy, U. S. D. A., Bureau of Entomology and Plant Quarantine
Railroad Sprayer in Operation for White-Fringed Beetle Control
I
NSECTICIDES are the substances used for preventing, destroying, repelling, or mitigating insects and allied classes of arthropods, such as spiders, mites, and ticks. More than seven thousand kinds of insects are estimated to cause economic losses in the United States. About 10 per cent of all growing crops are consumed by insect pests. In addition, insects attack stored corn, wheat and other grains, flour, dried fruits, nuts, woolen clothing, stored tobacco, wooden buildings, forests, poultry, livestock and other domestic animals, and man himself. Damage caused by insects in the United States may be conservatively reckoned at two billion dollars annually. Injurious fungi cause a loss of about one billion dollars a year. These losses would be much greater if liberal quantities of insecticides and fungicides were not used. The amount of insecticides and fungicides consumed in the United States is greater than is commonly realized. Estimates of the retail cost of those materials range from 100 to 200 million dollars annually. I n 1939 the following quantities of a few of the principal insecticides and fungicides were produced or imported : Lead arsenate, pounds Calcium arsenate, pounds Lime sulfur solution, gallons Pyrethrum flowers (1940imports), pounds Rotenone-bearing roots (1940imports), pounds
59,568,596 39,281,788 9,491,068 12,591,220 6,666,815
In addition, large quantities of sodium arsenite, copper sulfate, creosote, cryolite, sodium fluoride, formaldehyde, hydrocyanic acid, naphthalene, organic mercury compounds, kerosene, mineral oils, sulfur, and nicotine, and smaller quantities of many other substances were employed in fighting pests. I n spite of this array of chemical weapons, new insecticides and fungicides are needed so that we may reduce or eliminate the use of materials poisonous to man and domestic animals, such as the arsenicals and compounds of antimony, fluorine, lead, and mercury. As a result of the defense program there is at present a shortage of the chlorinated fumigants carbon tetrachloride, ethylene dichloride, and chloropicrin, and substitutes are needed. Imported products such
as pyrethrum and the rotenone-bearing roots may be cut
off or their supply seriously curtailed. What can be used in place of them? It is hoped that an answer may be found among the numerous synthetics now undergoing tests for insecticidal value. A discussion of the possibilities of new materials as insecticides and fungicides and of ways of improving old ones is especially appropriate a t this time of national emergency. Many of our present pest control materials can be made to go farther by improving their physical condition. Finer grinding increases the adhesiveness of phenothiazine and hence its efficacy in the orchard. A review of our knowledge of the relation between the particle size of insecticides and their efficacy will be presented by Smith and Goodhue. The relationship of chemical structure and insect toxicity is of interest to chemists and entomologists and if thoroughly understood would make the problem of developing new insecticides an easy one. Some of the papers bear on this subject. One of the most amazing discoveries in recent years is that of synergists that can be used with insecticides. I n physiology synergism is defined as cooperative action of discrete agencies such that the total effect is greater than the sum of the two effects taken independently-the opposite of antagonism, as in the action of the mixtures of certain salts or drugs. Sesamin from sesame oil, asarinin from the bark of the southern prickly ash, and certain related compounds, although practically nontoxic when dissolved in kerosene and sprayed upon houseflies, enormously increase the toxicity of a dilute solution of pyrethrins when added to it. This means that the supply of imported pyrethrum flowers may be augmented by the addition of cheaper products of domestic origin. I n spite of the growing shortage of many materials that enter into the manufacture of our most important insecticides and fungicides it seems probable that recent advances in the chemistry of pest control will enable the American farmer to increase the production of the food that “will win the war and write the peace”.
R. C. ROARK
