September, 1923
I N D U S T R I A L A N D ENGINRERING CHEMISTRY
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Chemistry in t h e Control of Plant Enemies New Achievements and Future Possibilities By Walter Collins O’Kane CROP PROTECTION INSTITUTE,DURHAM, N. H
OTHING is more important in human welfare than row, pours a cupful of kerosene into the pail, and knocks protection from the myriads of minute enemies in the beetles into this improvised device where the touch of a the plant and animal world. In this chemistry is drop of the liquid will finish off the pest, thus saving time now taking a leading part and is certain to make extraordinarv and energy and rendering his task more efficient. He has turned, ai-he should, to chemistrv. development. By t,he very nature of the case this ’ It is a long-step from this crude procmust be so. The whole tendency of man ew to the spraying, dusting, and fumiis to flock together, to subjugate the livgating that are now helping us to raise ing world and make it yield sustenance, crops. Rut it is not a long step in time. shelter, and all else. In vast areas this has The last twenty years have seen the greater part of the development, and a been going on for hundreds, or even thousands, of years. In other widespacesit period much shorter than that has witis only beginning. The tendency is as nessed a large proportion of the more important discoveries. The field is relastrong as human nature itself. and it is constantly assuming concrete shape. tively new, as work in chemistry goes, So it is that the human race is the and the progress that has been made is great upsetter of the natural balance in only a fraction of that which has been nature. We cut down forests, pull out achieved in other lines where the dethe stumps, plow the land, and plant a mands of industry on the resources of hundred thousand acres of potatoes. the chemist were stronger. We break up the sod of a million acres Within these few years striking adof prairie and seed it all down to wheat. vance has been made and materials have All this is necessary and, apparently, been developed that not only are imporis going to continue and to increase. The tant in themselves, but may rightly be same number of acres that supported a taken as forerunners of the progress that man and his family must come to supis sure to follow. It is interesting and port a score or a hundred, who are suggestive to consider some of these WALTER COLLIN3 O’KANE working to make other things that the developments. man and his family, and many others besides, want and p-DICHLOROBENZENE FOR PEACH BORER need. We cannot do this and expect natural forces to protect Take the peach borer, for example. There has been from harm the altered conditions that we have brought about hitherto no satisfactory control of this pest. Recent work in our fields and gardens. Amicroscopic, organism that would in New Jersey has shown that p-dichlorobenzene, applied cause a rust spot on a wheat plant might blow about in the in a ring near the trunk of the tree and covered with soil, wind and never find a suitable plant, if wheat grew only as affords efficient and economical control. Several hundred single, isolated specimens, scattered here and there in the thousand trees have now been treated through two or three midst of other vegetation. But that same microscopic seasons and the method is a proved success. Other possiorganism developing on a plant in a thousand-acre Dakota bilities of the substance are now being studied. field cannot fail to find a suitable host on which to develop. A beetle with black and orange stripes, hunting for wild SULFURSPRAYS potatoes in mountain highlands, may find the chances a thousand to one against it. But the same beetle in a MichiSulfur was one of the first elements ever to be used for gan potato field needs a dose of poison to put an end to its the control of plant diseases. Within the memory of most career. of fis a chemical combination of sulfur and lime came into The increased price of a product is bound to make it possible use as a spray to kill scale and to help control certain fungous to spend money to raise i t successfully, if it is something diseases. But nobody knew precisely how the thing worked. that human beings need, or want, or think they want. There It would act in certain fashion under one set of conditions, is no more doubt about that than there is about the rising but in other manner under other circumstances. It was of the sun to-morrow. And it is quite certain that the demand like a rifle that could shoot a bullet a long distance, but could €or foodstuffs with which to support life, for the products not always be aimed, and sometimes missed fire. that make life pleasurable, and even for those that bring Within the year much of this mystery has been cleared luxury, is not going to fall off. up and a possible means of controlling and enlarging the The means of avoiding losses from the various minute utility of sulfur has been discovered. It has been found enemies can take many forms. At the beginning the methods that in the changes that lime sulfur undergoes after it has are sure to be crude and laborious. The owner of the potato been applied as a spray, a new substance is formed which patch goes through it with a stick in his hand, knocks the is the really active agent in control of plant diseases. Furpotato beetles off onto the ground, and tramps on them. thermore, ways have been found which promise to make it But presently he carries a pail with him as he goes down the possible to control the formation of this substance and a t
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INDUSTRIAL A N D ENGINEERING CHEMISTRY
the same time to take lime sulfur out of the class of sprays that burn foliage and place it in the class of those that can be used quite safely in large amounts and in heavy concentration. SODIUM FLUORIDE FOR ROACHES Among the oldest of insect pests, as the geologists measure time, are the roaches. Prehistoric man may not have stayed long enough in one place to be bothered by them, but we know that they were in existence in those remote times quite as abundantly as they are now. There have been hundreds of roach powders, pastes, traps, and cures. Some of them do more or less good. But recently we have found in sodium fluoride a material that, rightly used, can eliminate roaches from overrun premises. The same material will kill ants. And so, probably for the first time in history, the human species can easily and securely rid itself of two prize nuisances in the insect world. POSSIBILITIES OF MERCURY Plant pathologists are well aware that in handling certain plant organisms in the presence of mercury they must protect them from the effects of its vapors. To what extent can this properly be utilized? How about its effects on animal organisms, such as insects? In parts of India there is a tradition that mercury, exposed in a tight container along with beans or other stored products on which the bean weevil has laid its eggs, will prevent these eggs from hatching. American experimenters have put this tradition to the test in recent trials and have found that the mercury does have a definite effect. The volatilization of the mercury is presumably very slow. A chemist’s balance would have difficulty in detecting the loss, except by exceedingly delicate measurements. CONTROL OF CEREAL GRAIKSMUTS The smuts of cereal grains have offered a serious problem to the expert in plant diseases. There was no mystery about the cause or the way in which they were carried. The difficulty lay in proposing a means of control that would be practical on a large scale. Two new measures are among the recent discoveries. The first of these turns to copper, a metal that has long been utilized in one way or another in fighting plant diseases. The other lies in the group of organic mercuric compounds that have been developed since the beginning of the World War. NEW USESFOR CARBON DISULFIDE Carbon disulfide, used for many years as a fumigant for grain weevils, is yielding new facts as a result of further study, backed by vision and resourcefulness. An experimenter, finding mosquito wrigglers abundant in a tub of stagnant water, dropped into it a teaspoonful of carbon disulfide. One would not expect any marked results, since the material is not soluble in water, except in slight degree. But in a minute or two the wigglers were in discomfort and in a few minutes more they were dead. The instance is suggestive. Other experimenters have tried an emulsion of carbon disulfide, greatly diluted with water, as a possible material for killing grubs a t work on grass roots. Curiously, they have found that moderate amounts of the material, thus emulsified and diluted, bring about a high percentage of kill. INSECT BAITSAND REPELLENTS We have only begun to explore the possibilities that may lie in the use of chemical compounds as baits for noxious insects, or as repellents. Every insect is a bundle of automatic reactions. Most of all, it is attracted or repelled by
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odors. This response largely controls the movement of an insect in search of food and, therefore, has a great deal to do with its harmful activity. If we can place before it an effective poison and can add to our dose some compound that will prove sufficiently attractive, we may persuade the pest to partake of our offering. Perhaps we can attract it away from the plant or product that it would injure in its feeding, and persuade it to eat something that is valueless while a t the same time working its own destruction. Thus, amyl acetate has been found to serve as an attractive ingredient in a poison bait for grasshoppers. But that is only a beginning. The corn-ear worm has a wide range of food plants. The adult that lays the eggs from which the worms hatch is attracted by corn silk. Investigators have taken strands of cotton twine, soaked them in the juice obtained by crushing corn silk, and have attracted the moths to these strands. By studying the composition of the silk, isolating the active principle that .attracts the moths, and then seeking the aid of chemistry to devise a substance that will simulate this principle, it may prove possible to devise a poison bait for this destructive pest that will protect our vast cornfields from the tremendous damage that they now suffer because of it. If this can be done, as appears not a t all impossible, we may be able to follow a similar procedure with reference to many other devastating pests. But the work and the possibilities do not end there. What shall we use as a poison? For many years our principal reliance has been placed on arsenic in one or another of its compounds. But we have reason to believe that the toxicity of various arsenical compounds to insects is by no means in direct proportion to the amount of arsenic that the compounds contain. Work is now in progress which is intended to throw light on this question, to help us to learn what forms of arsenic become most toxic within the digestive tract of insects and what influence may be exerted by the physical character of the material. We have observed, a t times, that some insects appear to be repelled by the presence of arsenical poisons on the plants on which they were feeding. Recent work with a new invader, the Japanese beetle, goes to show that so far as this insect is concerned the repellent effect is probably due to the discomfort caused by the irritating character of the first minute amounts of poison eaten. Investigators have tried the experiment, of administering with the poison spray an intestinal sedative, such as bismuth subcarbonate. Beetles fed on this mixture ate more of the poisonedleaves; more of the beetles consumed a fatal dose. Administration of bismuth subcarbonate on a large scale would not be practicable. But the principle involved is interesting and important. CONTROL OF THICKNESS OF SPRAY There is a big question, which experimenters are only beginning to touch on; that involves the addition of neutral or subsidiary materials to a spray in order to render it more effective through altering its physical qualities. With their assistance it may be possible to control, not only the covering qualities of a spray, but the thickness of the film deposited and its adhesive qualities. Conceivably, we may come to say, before long, that protection of apple foliage from a certain invading plant disease will require a film so many microns in thickness persisting through so many days, that less than this will be ineffective, and that more will be a waste of material. EFFECT OF MIXTURES Most of our spray schedules nowadays call for mixtures of this or that. We need to apply materials that will accom-
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September, 1923
INDUSTRIAL A N D ENGINEERING CHEiMlSTRY
plish more than one purpose and it is highly advantageous to do this in one operation. However, this turns the spray barrel into a chemical laboratory. Because Ingredient A is effective for one purpose and Ingredient B for another, it does not follow that A and B mixed together will retain their valuable characters in full degree, or even a t all. They may, instead, gain a new character that makes them highly harmful. The sprays to be worked out for the future must be devised, not only with reference to their individual qualities, but with reference' to their compatability one with another.
UNSOLVED PROBLEMS I n many of the new fields of inquiry we cannot even lay claim to a good start. Early blight once started in a potato field can, and sometimes does, sweep through it so rapidly that the ordinary grower, aware of the existence of the disease only when it has gained headway, cannot stop it before it has utterly destroyed his crop. The plant pathologist, taking it in time, can spray and check it. Rut what can we offer the grower that will prevent infection? A recent list prepared by a committee of plant pathologists gives more than a hundred plant diseases carried by seeds.
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More than fifty of these are endophytes living within the substance of the seed. Some of these diseases take enormous toll of our crops. How shall we treat seeds on the large scale in which they must be handled in farm practice and sterilize them successfully? Investigators have worked diligently to discover the cause of the mosaic diseases affecting various plants. We do not yet know what the cause may be. Without this knowledge we are badly handicapped in our search for means of control. I n certain sections of the East a serious plant enemy has become established, known as the potato wart disease. About the only recommendation that can be offered the grower is to change to varieties of potatoes that have been found to possess more or less resistance. We need to discover a definite and specific means of solving this and other equally unsolved problems. Nine times out of ten, perhaps ninety-nine times out of a hundred, our constantly increasing reliance in all this must be placed on discoveries in chemistry, working in intimate alliance with the biological sciences, with plant pathology, entomology, and bacteriology. It is an enormous field and the possibilities are equally tremendous.
Using Excess Power to Save Coal Electrical Generation of Steam for Heating and Process Work By E. H. Horstkotte GENERAL ELECTRIC Co., SCHENECTADY, N. Y.
FF-PEAK periods of demand for power on idle days when plants are shut down and Sundays and holidays often present important problems in fuel economy to plant engineers who are obliged to keep steam on the system for heating or other purposes. Heretofore, it has been necessary to keep at least one fuel-fired boiler in action, with the attendant expense of firemen, to say nothing of the fuel consumed. Textile mills, chemical plants, manufacturers of pulp and paper, and other industries, including central stations from whom such plants purchase power, if they do not make it themselves, are alike affected by this problem. OF GENERATISG PLANT DESCRIPTION The recent development of practical and economical means for the electrical generation of steam is affording an interesting solution to this problem of fuel economy through the use of an electric steam boiler which in effect may be said to form a complete steam-generating plant capable of operation with minimum attendance. The complete equipment consists of the shell with supporting feet, the electrodes, insulators, steam and water gages, safety vdve, circulating pump and motor, and a panel on which is mounted the control equipment (Fig. 1). The tank, or generator shell, is mounted vertically, and divided horizontally into two compartments, the upper known as the electrode compartment, where the actual generation of steam takes place, and the lower forming a self-contained hot well. Water entering the hot well from the feed-water pipe is forced into the upper chamber by a motor-driven centrifugal pump located on a short external pipe linc. From this chamber it flows back into the hot well through a number of small holes on the outer circumference of the dividing plate. This arrangement provides
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a continual circulation of heated water, the water level in the electrode chamber being held a t the desired level by setting the valve in the circulating pump discharge line. The upper, or electrode chamber, where the steam is generated, contains three large, round, iron electrodes rigidly supported from the roof, the current-carrying supporting rods coming in through specially designed insulating bushings. These bushings are provided with a small duct in the top leading to the outside air. Thus, if steam does succeed in leaking through the packing into the upper section of the bushing, it passes out freely instead of creating a pressure that might blow out the side of the insulator. The electrical operation resembles that of a three-phase arc furnace. Normally, the electrodes are submerged in the water, and the three-phase current passes through the water to the sides of the tank, or from electrode to electrode. The steam is generated by current flowing through the water, which is of high resistance. The temperature of all the water in the system is practically uniform. If the steam pressure lowers owing to an increased demand, rapid steam generation due to the high temperature of the water and the degree to which the electrodes are submerged quickly brings the pressure up again. Another operating feature is that since the water level is maintained by the adjustment of the throttle of the circulating pump, the energy consumption of the generator is not dependent on the operation of the feed-water pump. The supply of water in the hot well is regulated by an automatic feed-water regulator. Furthermore, when it is desired to reduce the load, the generator does not have to be blown, which means that water does not have to be pumped in subsequently against full pressure. The only energy losses in the circulating pump are the motor losses and the pump
