Bulletin STATE OF ILLINOIS HENRY HORNER, Governor DEPARTMENT OE REGISTRATION AND EDUCATION DIVISION OF THE NATURAL HISTORY SURVEY THEODORE H. PRISON. Chief Volume 21 BULLETIN Article 1 The Effect of Petroleum-oil Spra3^s on Insects and Plants M. D. FARRAR PRINTED BY AUTHORITY OF THE STATE OF ILLINOIS URBANA, ILLINOIS November 1936 STATE OF ILLINOIS Henry Horner, Governor DEPARTMENT OF REGISTRATION AND EDUCATION John J. Hallihan, Director BOARD OF NATURAL RESOURCES AND CONSERVATION John J. Hallihan, Chairman William Trelease, D.Sc, LL.D., Biology William A. Noyes, Ph.D., LL.D., Henry C. Cowles, Ph.D., D.Sc, Forestry Chem.D., D.Sc, Chemistry John W. Alvord, C.E., Engineering Edson C. Bastin, Ph.D., Geology Arthur Cutts Willard, D.Eng., LL.D., President of the University of Illinois NATURAL HISTORY SURVEY DIVISION URBANA, ILLINOIS Scientific and Technical Staff Theodore H. Prison, Ph.D., Chief SECTION OF ECONOMIC ENTOMOLOGY W. P. Flint, B.S., Chief Entomologist C. C. CoMPTON, M.S., Associate Ento- mologist M. D. Farrar, Ph. D., Research Ento- mologist S. C. Chandler, B.S., Southern Field Entomologist J. H. Bigger, B.S., Central Field Ento- mologist L. H. Shropshire, M.S., Northern Field Entomologist W. E. McCauley, M.S., Assistant Entomologist C. W. Kearns, Ph.D., Research Fellow in Entomology J. F. Alsterlund, M.S., Research Fellow in Entomology DwiGHT Powell, M.S., Research Fellow in Entomology L. R. Tehon, Ph.D., Botanist J. C. Carter, Ph.D., Assistant Botanist G. H. BoEWE, M.S., Field Botanist SECTION OF FORESTRY James E. Davis, M.F., Extension For- ester SECTION OF AQUATIC BIOLOGY David H. Thompson, Ph.D., Zoologist F. D. Hunt, Field Naturalist D. F. Hansen, A.M., Assistant Zoologist D. J. O'Donnell, M.S., Assistant Zo- ologist SECTION OF INSECT SURVEY H. H. Ross, Ph.D., Systematic Ento- mologist Carl O. Mohr, Ph.D., Associate Ento- mologist, Artist B. D. Burks, M.A., Assistant Ento- mologist R. E. Yeatter, Ph.D., Game Specialist W. H. Leigh, M.A., Assistant Zoologist SECTION OF PUBLICATIONS Carroll Chouinard, M.A., Editor This paper is a contributii '. the Section of Econ FOREWORD In 1919 the Illinois Natural History Survey began an Investigation of oil sprays for the control of insects. In 1925 the Crop Protection Institute established a research fellowship on oil sprajs with the Natural History Survey. This fellowship was supported by funds from the Standard Oil Co. of Indiana. This paper brings together data from the eight years of investi- gation 1925-33, and includes the data that appear to illustrate progress in the knowledge of oil sprays. Types of materials and tests The experiments have included tests on about 310 oil or oil-emulsion formulae, of which about 16 per cent were soluble oils and 84 per cent stock emulsions. In addition to these, various chemicals were included in many of the formulae. For purposes of discussion and comparison of the various emulsions the information is grouped under general headings referring to the specific insects and plants used in the experiments. Avery limited number of emulsion formulae were tested under field con- ditions for more than one season. The greater portion were tested under field conditions for only one year. Laboratory studies were made upon all of the formulae to determine their physical properties and toxicity to bean foliage. A limited number of tests were performed on insects to evaluate the insecticidal properties of each emulsion. Those formulae which looked promising as a result of information gained in the laboratory were tested under field conditions the following season. Present knowledge of oil sprays As tangible results of the investigation, a miscible oil and a white-oil stock emulsion have been developed. In the investigation of these products and the study of their related formulae, a fund of constructive information has been compiled that has been of great assistance in the interpretation of results. This information has added greatly to our understanding of some ot the factors affecting the reactions of petroleum oils on insects and plants. Indicative of present knowledge concerning oil sprays are the following : The use of oil emulsions for codling moth control in late-brood sprays, particular- ly when mixed with nicotine sulfate, is very promising. Sprays of oil emulsions for late-biood codling moth larvae have given excellent results in the reduction of lead arsenate residues. The larvicidal limits of oil emulsions are fairly well established. The use of oil emulsions with lead arsenate sprays shows promise in the control of codling moth larvae. The use of petroleum oil as a carrier for plant poisons is recognized. Oil emulsions are giving a control of scale insects superior to all other sprays for scale. Acknowledgments The author wishes to thank the Crop Protection Institute, its committee, and chairman Professor W. P. Flint for their guidance in the development of this project; the Standard Oil Co. of Indiana for the funds used in the project and for experimental samples prepared and furnished through its en- tomological staff and chemists; the Illinois Natural History Survey, Urbana, for permission to use the equipment employed in the investigation; members of the staffs of the Universitx' of Illinois and Iowa State College for experimental material and assistance in the carrying on of the investigation, taking of data and evaluation of results ; and Dr. L. L. English, former inves- tigator of this project, who has furnished much time and eiifort in the collec- tion and evaluation of data. Definition of Terms Concentration of emulsions refers to measurements by volume. Lead arsenate is acid lead arsenate, the powdered commercial product marketed for insecticidal purposes. Miscible or soluble oils are clear oil-like emulsions containing very little water. In these a soap emulsifier is dissolved into the oil. Upon the addition of water the miscible oils disperse to form a milky white emulsion of very small oil-droplet size. The commercial oils Dendrol and Sunoco are exam- ples. Paraffin oil or unsaturated oil is not as highly refined as technical white oil (which see) and contains unsaturated hydrocarbons in varying amounts depending on the degree of refinement. The degree of saturation is expressed as unsulfonated residue and is determined by a standard procedure known as the Whiting method. Quick-breaking emulsions are made in the spray tank with or without addition of some emulsifying agent. The emulsion depends upon the agita- tion to break up the oil into droplets. The oil droplets are very large and loosely emulsified, so that the oil phase may separate either on standing or soon after application. For certain insects such as leaf rollers and case- bearers, they are superior to the more stable emulsions. Stock emulsions are oil emulsions of a pastelike consistency. They gen' erally contain water as a separate phase. Boiled fish-oil soap emulsion is an example of this type. Technical white oil is an oil from which the preponderance of unsat- urated hydrocarbons has been removed, but it is not of medicinal grade. A technical white oil, or saturated oil, is practically inert chemically. Viscosity, as measured by the Saybolt test, is the resistance to flow of a given volume of oil through a given orifice at 100° F, and is expressed in seconds. Urbana January 1, 1936 M. D. F. Contents Foreword iii Types of materials aiul tests. Present knowledge ot oil sprays. Acknowl- edgments. Definition ot terms. Properties ot Oil Emulsions 1 Plant tolerance limits viscosity. Less stable emulsions most toxic. Spray methods regulate coverage. Stability determines mortality. Kffect of Petroleum Oils on Plants 3 Oils tile modern insecticide. Tolerances variable, specific. Normal metabolism disturbed. Measure of injury unsettled. .Annual dormant sprays safe. Unsaturated oils highly toxic. Saturated oils generally safe. Smaller droplets more injurious. Emulsifier controls droplet size. Insecticide Tests with the Emulsions 8 Codling moth. Red spider. San Jose scale. .Aphids. Oyster-shell scale. Kuropean elm scale. Fruit-tree leaf roller. Fleas. Oils with Fungicides 27 Dormant oils with fungicides. Summer oils with fungicides. Bililiography 29 Testing Codling Moth Sprays.— Top, Apparatus devised by Farrar and McGovran to secure uniform deposit of spray on apples. At tlie left is sliown a 110-volt, 60-cycle (1800 rpm'l one-sixth horsepower stir motor with reduction gear. The stir rod buffers against a No. 13 rubbci stopper supported between two roller-skate wheels as bearings. On the lower end of the shaft carrying the stopper is a heavy-walled rubber tube extension that buffers against the rim of an auto wheel covered with friction tape to reduce slipping. The wheel is part of a whirligig that rotates a group of six experimental apples while revolving each apple separately. Moving at 8 rpm, the wheel turns six skate wheels, supporting an apple apiece, at 27 rpm against a fixed 6-inch buffer wheel. At right is a sprayer constructed for use with compressed air, spraying with 25 pounds pressure. The spray mixture in the jar is stirred by an agitator driven by a compressed- air turbine. Bottom, Rack of test apples used in laboratory tests of codling moth sprays. ILLINOIS NATURAL HISTORY SURVEY BULLETIN VOL. 21, ART. 1 NOVEMBER 1936 The Effect of Petroleum -oil Sprays on Insects and Plants M. D. FARRAR PROPERTIES OF OIL EMULSIONS The ratio between saturated and unsaturated hydro- carbons in an oil determines to a large extent the [use of that oil as an insecticide on either dormant or non- dormant plants. The viscosity, volatility and degree of dispersion are important properties which affect both plant tolerance and insecticidai eflficiency. Spreading properties of unit volumes of spray are nearly identical as to coverage and time. Preparation of emulsions for these experiments was by the Whiting method. SATURATION, or the ratio between saturated and unsaturated hydrocar- bons, has sharpl}- di\ided the usage of oil sprays into two distinct fields. The works of Gray & deOng (1926), deOng. Knight & Chamberlin (1927), English (1928) and others show that the oils con- taining the larger quantities of unsaturated hydrocarbons are the more likely to cause plant injury under comparable conditions. Extensive experiments indicate that the less highly refined oils are safe to apply on dormant trees if they are properly emulsi- fied. Because of the lower cost of this grade of oil its use in dormant sprays has become general. Plant Tolerance Limits Viscosity The viscosity of oils used in tree sprays must be kept within the limits of plant tolerance. Oils of less than 40—50 seconds of viscosity are \ery difficult to combine into a stable emulsion. Although somewhat safer to use on plants, these light-viscosit\ oils disappear too rapidly to have a good insecticidai value. Knight, Chamberlin &: Samuels (1929) feel that a 60-second vis- cosity oil represents about the upper limit of plant tolerance and that oils of higher viscosities must be used with caution if seri- ous ultimate injury is to be avoided. Most authors agree that the lighter oils are safer on plants and generally recommend the lightest oil that will give proper control of the insect involved. Temperature under which an oil is used in the field should determine the proper viscositv, accordint' todeOng(1931), although Green ( 1 927 ') did not find viscosity a factor for toxicitx in dormant spraying. Oils of 60—12.S seconds viscosity are now being used in the manufacture of the greater part of the com- mercial brands of oil emulsions. Less Stable Emulsions Most Toxic Volatility is a property that some authors have considered important in petroleum oils for use in tree sprays. Although per- haps of some importance its significance ha< not been fully accepted by all workers. The property of volatility is by no means iden- tical with that of viscosity, nevertheless it is closely associated with viscosity. Ac- cording to the findings of Knight, Cham- berlin & Samuels (1929), the effect of volatility "due to the enclosure of the oil in the intercellular spaces ... is unquestion- ably negligible in comparison with trans- location." In this paper the author has not considered \olatility an independent prop- erty of the oils used in the emulsions tested. The emulsifier plays a very important role in the performance of oil emulsions, as is shown bv the work of deOng & Knight (1925), deOng (1926), deOng, Knight 5: ILLINOIS NATURAL HISTORY SURVEY BULLETIN \'ol. 21,Art. I Cliamln-rlin (1*^27) and others. Oil emul- sions that incorporate excessive amounts of cmulsifier are \ ery easily emulsified but are not as efficient for the control of scale as are less stable emulsions. English (1928), working with aphids, San Jose scale and oyster-shell scale, clearly demonstrated that high mortality was associated with emul- sions exhibiting the quicker breaking prop- erties. Spray Methods Regulate Coverage The total volume of an\' spray material required to cover a certain block of fruit applied. This fact is in accordance with the findings of Swingle & Snapp (1931), and it is brought out also in the records of commercial orchards which use large amounts of materials for each spray. In well-equipped orchards the variations can usually be accounted for by adverse weather conditions. Additional proof that the volume of spra> material necessary to cover a unit number of trees is relatively constant was given in a series of tests that made use of commercial oil W at 2 per cent concentra- Table 1.—Properties of experimental oils.' Type or On. and Number No\ember 1^36 farrar: effect of petroleum. oil sprays oil, water or emulsifier phases of these emulsions often changed the degree of dis- persion. The difficulty of classification made impractical the consideration of par- ticle size in the experimental white-oil emulsions. It is generally recognized that the less dispersed oil emulsions separate- faster and are more toxic to insects. A'lost miscible oils and many of the stock emulsions were prepared by a standard technique worked out in the Standard Oil laboratories at Whiting, Ind. Stock emul- sions incorporating inert emulsifiers were emulsified by colloid mills, capable of pro- ducing emulsions of uniform dispersion of oil droplets in the technical white-oil emul- sions. (For analysis of oils used see Table EFFECT OF PETROLEUM OILS ON PLANTS The physical properties of oil emulsions cannot be associated with some forms of plant injury that follow applications of oil sprays. Such plant disturbances are associated with general vigor, stage of growth, soil mois- ture and food relations. Petroleum-oil emulsions formed with soap are generally toxic to foliage irrespective of the saturation or viscosity of the petroleum oil. The amount of emulsifier present in an emulsion pre- determines to some extent the physical nature of the emulsion and to a greater extent its insecticidal value. The emulsions which possess the larger oil droplets are the more toxic to insects and less toxic to plants. The viscosity of a petroleum oil determines to a limited extent its safety to growing plants. The lighter oils, 50 seconds of viscosity or less, are less toxic to plants but are not efficient insecticides. Oils of greater than 100 seconds of viscosity tend to create physiological disturb- ances within the growing plant. A laboratory study of the larvicidal efficiency of emul- sions indicates only a limited possibility of increasing the mortality of codling moth larvae by changes in the physical properties of an emulsion. The technical white-oil emulsions are relatively safe on foliage if they possess the proper degree of saturation, viscosity, oil-droplet size, and an inert emulsifier. Previous to 1900 many cases of plant injury were reported ' from the spraying of plants with petroleum oils. It is not sur- prising to find injury occurring early in the -Manufacturers of commercial oils used in tliise tests: .Sun Oil Co., B. G. Pratt & Co.. Sherwiu-Willianis Co., California Spray-Chem- ical Co., Shell Oil Co.. Schaefter Bro.«. & Powell, and Standard f>il Co. of Indiana. 'According to Liodeman (1S06), tJoeze was the first to recommend the use of oils on plants. In 1763, .T. A. E. Doeze wrote, "petroleum, turpen- tine and other oils are also recommended, but care must be taken in their use, since they act upon the plants, making them sick or even kill- ing them." liodeman also credits William For- syth as the first (1800) to call attention to the use of train (whale) oil against coccus or scale insects on plants. The first record of petroleum oil as an insec- ticide in Anierica is a recommendation in 18r,G development of oil sprays. About 1900 the use of petroleum oils became more general and information became available as to the more suitable oils and emulsion types that ctjuld be safely used on growing plants. Louring this same period there was rapid development in the machinery necessary for the proper preparation and application of emulsions. Oils the Modem Insecticide Entomologists now recognize that oil spra\ s ser\'e as very important weapons for the control of many dangerous pests, such as scales, mites, aphids, leaf rollers, case- bearers, codling moth and oriental fruit moth. Petroleum-oil emulsions are now available that are adaptable for definite insecticidal purposes with a minimum of danger to the host plant. \'olck (1903) published the first com- prehensive paper on the effect of petroleum oil when used on plants as an insecticide. In this paper he concluded, "by far the greatest cause of injury to \egetable tissue is brought about by the penetration of the oil applied, into the interior of the plant." He also found the lighter oils less injurious than heavy oils and that the degree of injury depended upon certain physical fac- tors. Some of the factors listed by \'olck are the condition of the plant, type of oil, amount of spra\ used, whether the spray is applied to the upper or lower leaf surface, and temperature and humidity at the time of spraying. He demonstrated a physical injury from oil that he attributed to "insu- lation" or sealing over of the parts of the plant ; this insulation interfered with both respiration and transpiration of the plant. The chemical effects caused by the petro- leum oils used b\- Volck can now be largely corrected by employing the highly refined white oils, which contain a minimum of unsaturated hydrocarbons. tci use kerosene undiluted. The oil was to be applied by means of a feather on citrus trees for the control of citrus scale. Kerosene was fust employed as a spray in 1868 by Henry Bird. Newark, X. .T. He used a mixture of kerosene, soaii and water for the control of the currant worm. It was not generally used as an emulsion until recommended bv A. J. (7'ook in 187S. By 18S2, H. O. Hubbard had developed a satis- factory formula for kerosene emulsion, using soap as an emulsifier. Kerosene and other lig-ht petroleum oils were used quite generally either as emulsions or as mechanical mixtures previ- ous to 1900, followed by distillate-water me- chanical mixtures in 1902 and bv miscible oils in 1904, according; to Ma.son (1928) and Essii? il9:!l). ILLINOIS NATURAL HISTORY SURVEY BULLETIN Vol. 21, Art. 1 Tolerances Variable, Specific Volck (1903) found that the important injuries to citrus leaves by oil are general and not local. This observation has been substantiated in more recent work by the determination of rather definite plant tol- erances to oil sprays. No rules can be estab- lished relative to the tolerance of plant species to oils, but we do know within limits the amount of certain petroleum oils that can be applied with relative safety to the more important trees and plants. It is now well established that a dormant tree will withstand higher dosages of less refined oils than the growing tree. The type of oil that may be used with safety to the plant will depend to a great extent on the season of the year when it is applied. The accumulative effect of oil sprays has been mentioned by Volck (1903), Yothers (1913) and others. It is pronounced dur- ing the active growth of the plant and becomes less evident as the plant approaches dormancy, at which time the effect appar- ently disappears. Burroughs (1924) stated, "from theoret- ical considerations and from observations and experiments, it is quite certain that a covering of oil on the surface of the plant organ may affect the physiological processes of that organ. It is probable that under some conditions the effect of the oil may be infinitesimal." Normal Metabolism Disturbed Herbert (1924), working with prunes, found the greatest plant stimulation asso- ciated with the heavy types of miscible oils. He correlated the degree of stimulation with the moisture and food relations of the soil and the season of the year when the trees were sprayed with the oil. deOng (1926) also found a correlation between the season of spraying and the effect on French prunes. In his experiments, extend- ing over two years, sprays applied in No- vember before the trees were fully dormant slightly retarded development, December sprays had little effect, January and early February sprays stimulated, while sprays applied between February 15 and March 15 retarded development. Knight, Chamberlin & Samuels (1929) determined histologically the distribution of the petroleum oil in the plant tissue fol- lowing an oil spray. They found that the saturated white oils were absorbed by the tissues and not volatilized, as considered by some authors. The translocation of the absorbed oil was traced from the leaf sur- face to its final deposition in the large stor- age cells of the pith and the old wood fiber of the xylem. During the period of oil pene- tration and initial translocation, transpira- tion was sharply decreased and respiration enormously increased. Knight and his co- workers attributed the metabolic disturb- ances to physical rather than chemical handicaps imposed by the intrusion of the saturated petroleum oils into the plant tis- sue. Ginsburg (1929) found that apple foliage sprayed four times between July 12 and August 24 increased in chlorophyll content from 28 to 47 per cent in the two apple varieties tested. This secondary effect of oil sprays, that of intensifying the green appearance of the oil-sprayed foliage, has been reported by numerous workers with oil emulsions. Working with excised twigs, Kelley (1930a) found that "Saturation of the heavier oils, comparable to those used in commercial spraying, was not important in either the dormant or delayed-dormant periods. It was relatively unimportant in foliage applications." Measure of Injury Unsettled The works of Volck (1903), Yothers (1913), deOng (1926, 1928b, 1931), English (1928), Knight, Chamberlin & Samuels (1929), Kelley (1926, 1930a, b), Ginsburg (1929, 1931a, b) and others demonstrate that oils applied to foliage pro- duce certain physiological effects on the trees. As yet no one has advanced a good criterion for classifying these physiological effects as injury resulting from an oil spray. Woodworth (1930) proposes certain terms which may be useful in classifying these effects. It is true that certain oils will injure or burn more than other oils under a comparable set of conditions, but it has never been possible to show that a certain property of an oil, if present in an emul- sion, will result in foliage injury. In this paper, injury is considered as visible changes in the normal leaf tissue following the application of an oil spray. This type of injury usually is evident on the margins or tips of the terminal and adjoining leaves. A part of the difficulty in dealing with emulsions lies in the fact that every emul- November 1Q36 farrar: effect of petroleum-oil sprays sion prepared is an individual colloidal sys- tem possessing properties distinctive from every other emulsion. Although this con- dition is literally true, the emulsions tested in this work were approximately the same since they were prepared in the same way and from very similar materials. It was found possible to duplicate quite closely for- mulae that had been used in previous tests. Annual Dormant Sprays Safe Consistent annual spraying of deciduous fruit trees in the dormant stage with good oil emulsions has produced no apparent injury to them, according to Yothers (1918), Burroughs (1924), Newcomer c increase foliage injury. The injury shown in items 6, 7 and 8 was probably caused by the copper, sulfur or sodium fluosilicate mixed with the white- oil emulsions. The formulae containing copper injured in 51 per cent of the cases, and those with sulfur in 70 per cent of the cases, where they were tested. Technical white oils, item 9, made up as a stock emulsion with a soap emulsifier did not injure in the limited number of trials given. The same oils combined as a misciblc oil injured in 14 per cent of the tests. Smaller Droplets More Injurious Petroleum oils containing as much as 9 per cent of unsaturated hydrocarbons will cause injury in most cases if they are com- bined with soap emulsifiers. The soap einulsifier, item 14, is no doubt responsible for some of the injury obtained with emul- sions containing soap. The miscible or solu- ble oils, items 11 and 12, give relatively more injury than do the stock emulsions, item 13. The smaller oil-droplet size and greater stability of the miscible oils are responsible to some extent for the injury that follows the use of miscible-oil emul sions. It is evident that, other factors being equal, the emulsions with the smaller oil droplets are the more likely to cause injury to foliage. Novcmlicr \'>ib farrar: effect of petroleum-oil sprays In Talile 2 ;i large number of cases are reported where no injury was observed with any of the sprays listed in items 1 to 14. These occurrences are significant be- cause they explain to some extent the con- fusion resulting from reports of injury occurring in the individual experiments of all workers. Some of the recent work of deOng. (1^26), deOng, Knight &: Chamberlin (1^27). and Smith (1029, 1030 and 1031 1 has again raised the problem of applying oils to plants without the aid of an emul- stability of such an emulsion was almost negative and the oil droplets so irregular and unstable that they were difficult to measure. The oil drops were very large and coalesced rapidly. Neither of these oils injured foliage at l'^ per cent concentra- tion but the less saturated oil spotted the fruit of apple. Emulsifier Controls Droplet Size In items 3, 4 and 5 a technical white oil was used that contained a product known as "butylacet\l resinoleate," which has been Table 3. —Relation between emulsifier, droplet size, saturation and foliage injury to apple. Sprays applied to foliage at 1 ' -j per cent concentration of oil in the water phase. C O M P O S I T I c Viscosity Saturation seconds at 100° F perceutang Stabilil Oil- Injury droplet to Size Foliage Paraffin oil Paraffin oil 3 ILLINOIS NATURAL HISTORY SURVEY BULLETIN Vol. 21, Art. 1 experiment as a comparison with the other emulsions. It contains a technical white oil with an inert emulsifier, has quick-breaking properties and is relatively safe on apple foliage. Soluble oils 8800 and 8790 contain the same ratio of emulsifier as soluble oil 17 but are prepared with 60 and 83-second-viscos- ity white oils respectively. In items 7, 8 and 9 there was no marked difference be- tween the technical white oils and the less saturated oil in their injury either to fruit or foliage when they were emulsified with certain soaps. Considering the graduation in the oil- droplet size and stability between items 1, 3, 5 and 8, all containing technical white oils, it is evident that the emulsions with the smaller oil droplets and greater stabil- ity are the more injurious to apple foliage. Similar differences are exhibited between items 2 and 9, both of which contain oils with a lower sulfonation test. IIISECTICIDE TESTS WITH THE EMULSIONS Codling Moth Carpocapsa pomonella (Linn.) White-oil emulsions are practical in the late-brood codling moth sprays in order to avoid arsenical residues on the fruit. The white-oil emulsions alone are not equivalent to lead arsenate in larvicidal efficiency but when combined with nicotine sulfate they are comparable to lead arsenate in the control of the late-brood codling moth larvae. Addition to emulsions of extracts of plant poisons such as pyrethrum, derris or tobacco materially increases toxicity of the emulsions as contact insecticides. Of the plant poisons, nicotine alone was stable to exposure under field conditions. Toxicity to foliage was not influenced by the addition of plant extracts to the emulsions. White-oil emulsions can be used as ovicides in codling moth control either alone or included in the lead arsenate sprays. The combined spray has excellent ovicidal and larvicidal properties. FIELD TESTS IN CONTROL OF CODLING MOTH The codling moth is by far the most destructive insect encountered in the pro- duction of apples. The annual abundance of codling moth and the difficulty of secur- ing an adequate control by the use of poison sprays have given this pest a role as limit- ing apple production, particularly in the sections where apples are grown commer- cially. In seasons of abundance the late- brood larvae will destroy 10—40 per cent of the marketable fruit. This condition Lead Arsenate November 1936 farrar: effect of petroleum-oil sprays efficiency of oil emulsions with lead arse- nate. Spuler & Dean (1930) state, "when oils are combined with lead arsenate the resultant spra\- has an ovicidal value equal to that of oil alone and a larvicidal value greater than that of lead arsenate alone." In their tests a three-fourths per cent actual oil ga\'e 80—95 per cent kill of cod- ling moth eggs. Newcomer & Mothers (1932) suggest use of "a medium oil, hav- ing a Saybolt test of 65—75 seconds and a high sulfonation test applied in a proper- 1 LEIAD ARSENATE 12), n/^s LIME C4), WATER (lOOJ ^" 10 ILLINOIS NATURAL HISTORY SURVEY BULLETIN \'(ll. 21, Alt. Mothers (1932) found that from 80 to 97.6 per cent of tlie eggs failed to hatch if spra) ed with a 2 per cent heavy-oil emulsion and that 64.6 per cent of the eggs did not hatch if laid within seven days after appli- cation of an oil spray. The ovicidal effect obtained from oil sprays will explain in many cases wh\ the same oil spray has gi\en variable results in succeeding years and in different orchards. Since 1927, orchard tests have been con- ducted to compare the eflSciency of oil-emul- sion sprays with that of lead arsenate sprays. The schedule followed for dates of furnished the fruit used in scoring spra\' performance. Apple pickers gathered the fruit from the inside quarters of these trees. A 1000-apple sample was taken from this fruit to be graded in scoring the plot. The population of codling moth varied in the test orchards from liglit to extremely heavy, including in the five years of records repre- sentative orchards in the commercial apple- growing sections of the state. A summary of five years of data is given in Table 5 and fig. 1. The relative control given by all of the sprays as compared with no spraying is striking, especially in the Table 5.—Codling moth control in the orchard over a five-year period. Orchard tests were conducted in commercial orchards of western, central and southern Illinois. A test was a count made on 1000 apples taken from the four center trees of a test block. Spray Treatment r Secoxd and Third-br Item Larvae Tests Cent Oil emulsion stock 200 at 2% Oil emulsion stock 5 at 2% Oil emulsion stock 200 plus pyrethrum. at 2% Oil emulsion stock 200 plus nicotine (Ni-SO^ 3-^ pt. per 100 gals.), at 2% Control, no spray all ; 1.8 November l<53b farrar: effect of petroleum-oil sprays 11 Item 1 can be used as a basis of compari- son since this treatment conforms with tlie recommendations for the control of second and third-brood codling moth larvae. Lead arsenate was applied at 2 pounds per 100 gallons in 1927, 1928, 1929 and 1930, and at 4 pounds per 100 gallons in 1931. The change in 1931 gave lead arsenate an advantage, as no change was made in the oil-spray schedule. In items 1 and 2 a direct comparison is shown between lead arsenate plus hydrated lime ( 1 pound of lead arse- nate to 2 pounds of lime) and oil emulsion at 2 per cent concentration. The results in 1927 were decidedl\ unfavorable to the oil- sprayed plot. The years 1928 and 1930 showed 5 and 16 per cent fewer entrances in the oil-sprayed fruit. In 1929, 55 per cent, and in 1931 18 per cent, more larvae entered the oil-spra> ed fruit. For the five- '^oOO O o ^ O o oO o oO< Oo o o Fig. 2.—Oil stock 200. X490. year average, 19.5 per cent more larvae entered the oil-sprayed than the lead arsc- nate-spra\ed fruit. Items 2 and 3 show the performance of two commercial white-oil emulsions. The droplet size of these t\\o oils is illustrated b\ microphotographs, figs. 2 and 3. The oil-droplet size in stock 200, fig. 2, is much larger. The emulsion contains 15.6 per cent less oil, has a relatively low wetting property, and gives a very spotted type of covering. Commercial oil stock 5, fig. 3, has small oil droplets, high wetting, and leaves a smooth, even oil covering. If the protection given fruit from codling moth larvae and tlie safety to fruit and foliage be considered, oil stock 200 is superior to tile other oil emulsion for second-brood codling moth control. White-oil Emulsions with Pyrethrum and Derris Poison plant-extracts from pyrethrum ilowers, tobacco or derris root, mixed with stock emulsion 200, have been given many field trials. Data covering the work with codling moth are given in Table 5, items 4, 5 and 6. Emulsions containing extracts of derris and pyrethrum were found to be less toxic to codling moth larvae under lield conditions than the nonimpregnated emulsions. Exposure of derris or pyre- thrum products to the action of sunlight and oxygen destroyed their activity toward insects, as is clearly demonstrated by lab- orator}' tests. These same oil emulsions, when tested against codling moth larvae in the laborator>' after a relati\ely short exposure to the air, consistently gave per- formance superior to nonimpregnated emulsions. White-oil Emulsions with Nicotine The use of nicotine with oil emulsions is finding a place in the oil-spray program Fig. 3.—Commercial oil stock 5. X4y0. for second-brood codling moth, according to Herbert ( 1931 ). The field results with nicotine and oil spra\s. Table 5, item 5, show it to be equal or superior to lead arsenate. This is in line with the results of Herbert & Leonard (1929), Regan (1930), Leonard (1930), Spuler .^ Dean (1030) and Webster (1931). The most favorable mixture of oil and nicotine has been that (jf summer-oil emul- sion at 1 per cent concentration with nico- tine sulfate in dilutions of from 1 :800 parts to 1 :1600 parts. Free nicotine used in place of nicotine sulfate will give a some- \\hat quicker kill but is not so effective a mixture as is the oil with nicotine sulfate, riie relati\ e persistence of the two nicotine products has not been tested in the field under Illinois conditions. The 1932 report of the Western Cooperative Codling Motli Conference recommends oil and nicotine spravs as the most practical sprays for late- brood codling moth larvae where lead arse- nate cannot be used. 12 ILLINOIS NATURAL HISTORY SURVEY BULLETIN V'ol. 21, Alt. 1 water to a 2 per cent concentration by vol- ume and applied at once to test apples by standardized methods to be described. Laboratory Technique The method used in rearing codling moth larvae for larvicidal tests was de- scribed by Farrar & Flint (1930). The apparatus and technique for handling the apples and the larvae were developed in the present work.* The method of applying the spray to the fruit was standardized as Table 6.—Larvicidal efficiency of oil sprays tested in the laboratory against newly hatched codling moth larvae. No. Average ORMULAE Relative Tested Efficiency LABORATORY TESTS IN CONTROL OF CODLING MOTH Standardized laboratory tests were used in making close comparisons between oil emulsions. Many combinations of insecti- cides were tried in the search for improved killing power of the oil sprays. White-oil stock emulsion 200 served as a basis of com- parison for oil emulsions. This formula con- tains 64.4 per cent of a technical white oil of 83 seconds viscosity, with an inert emul- sifier. The formula was varied with respect 1 November 1936 farrar: effect of petroleum-oil sprays 13 PERCENTAGE CONTROL CONTROL MISCELLANEOUS EMULSIONS COMMERCIAL WHITE OIL STOCKS 2 STOCK \B00 MISCELLANEOUS EMULSIONS CROUP n 10 20 30 40 iO • 60 70 80 90 5 WHITE OIL 200 , savbolt test WHITE OIL 200 WITH FUNGICIDES 1 rURFURAMIDE 2 SULFUR 3 BASIC COPPER SULFATE 4 FURFtJRAL b BETA NAPHTHOL WHITE OIL 200 7 WITH \0°/o FLUOSILICATES 1 CALCIUM 2 SODIUM 3 BARIUM WHITE OIL 200 8 WITH VARIOUS EMULSIFIERS I GUM 2 CUM I REDUCED AMOUNT} 3 TRIETHANOLAMINE 4 COULAC MISCELLANEOUS EMULSIONS LEAD ARSENATE 10 (2).LIMEC4), WATER (100) WHITE OIL 200 II WITH PYRE THRUM AND FUNGICIDES 1 SULFUR 2 BORDEAUX 3 FURFURAMIDE 4 COPPER SOAP 5 BETA NAPHTHOL 6 FURFURAL WHITE OIL 200 WITH DERRIS PRODUCTS 1 DERRIS, WATER, OIL 2 cube' EXTRACT 3 ROTENONE 4 DERRIS, OIL 5 DERRISOL, WATER 6 DERRIS WATER 7 CROUND DERRIS htB.PEfi GAL 8 ROTENONE, PENETROL 9 GROUND DERRIS ILB PER GAL JO GROUND DERRIS 2LBS PER GAL WHITE OIL 200 13 WITH PYRETHRUM PRODUCTS SAyBOLT TEST 150 5 GROUND PYRETHRUM 6 STABILIZER OF PYRETHRUM WHITE OIL 200 14 WITH NICOTINE PRODUCTS 1 FREE NICOTINE 2 NICOTINE SULFATE EMD E) EE) ED E) ED 20 30 40 50 60 70 80 90 PERCENTAGE CONTROL Fig. 4.—Laboratory tests of sprays to control codling moth in Illinois, showing relative efficiency of 13 groups of materials. Each white dot marks the average efficiency of a series of tests. larvae were considered a series and a check apple with 10 larvae was included with every two series. Seven series of tests were conducted with each emulsion. In the total 14 ILLINOIS NATURAL HISTORY SURVEY BULLETIN \'ol. 21,Art. I test a material thus received 21 or more trials, in which 210 codling moth larvae were given opportunity to enter the sprayed fruit. Because of the natural variation of larval vitality it was found adxisable to conduct the seven smaller tests of three apples each over a period of days rather than to make a large single test. Scoring of treated and untreated fruit was done five days after infestation. All data obtained were calculated against the number of larvae entering untreated fruit. The relative efficiency for each emulsion has been calculated on the basis of the con- trol afforded b\' the untreated fruit. For purpose of discussion, emulsions that are related in certain ingredients are grouped together, as shown in Table 6. The emulsions within each group, and the several groups as a whole, have been ar- ranged to show the relative efficiency of the sprays against codling moth larvae. Figure 4 is a graphical illustration of the exact performance of each material tested. Each white dot in the columns of this graph represents the average efficiency of a series of laboratory tests on a respective emulsion, the length of the column then showing the range of efficiency. White-oil Emulsions The property of an emulsion can be altered by changing the viscosity of the oil. The average efficiency given by 15 changes in viscosity was .34.2 per cent. The changes included cover the entire range in oil vis- cosities suitable for tree-spray oils. This control is only 2.2 per cent greater than that given by the 83-second oil, which is the same as commercial oil stock 200. The total range in the results by changes of vis- cosities alone is not much greater than that exhibited by the commercial white-oil emul- sions. Laboratory data, fig. 4, item 5, would indicate that oil viscosities under 83 seconds are not so satisfactory as the higher- viscosity oils for the killing of codling moth larvae. The most efficient white-oil emulsions were obtained by varying the concentration or type of emulsifier. The most efficient emulsion contained the emulsifier Goulac, lignin pitch, which according to Hurt ( 1931 ) is a by-product of the paper indus- try. Physically this emulsion has undesir- able properties. It is relatively unstable, lias large irregular oil droplets, and tlu' stock tends to jell on standing. The amount of emulsifier included in an emulsion will determine within certain limits the type of emulsion that will be formed. When the percentage of emulsi- fier to the oil and water phases is reduced, the size of the oil droplets tends to increase. In the cases of the emulsions shown in fig. 4, item 8, where the gum emulsifier was greatly reduced, the emulsion formed was stiff, had larger oil droplets, and was more difficult to dilute than was oil emulsion 200, item 5. Although the physical change brought about by reduction of the emul- sifier resulted in somewhat higher kill of codling moth larvae, the characteristics of tiiis gum emulsion make it impractical. In general, under laboratory conditions the oil emulsions containing the smaller oil droplets did not give so high a kill of codling moth larvae as did those with the larger oil droplets. The emulsion contain- ing a triethanolamine emulsifier, item 8, did not follow this trend as did some of the other white-oil emulsions. Need of a fungicide that can be safel\- combined with an oil emulsion as a summer spray has long been recognized. In this study a number of possible fungicides were tested. Fungicides typical of those tested are shown in fig. 4, items 6 and 1 1. Fungi- cides mixed with an emulsion tend to reduce the efficiency of the emulsion below that of the emulsion without the fungicide, rhis fact is particularly true of those fun- gicides tiiat have the property of adsorption of a part of the emulsion to the surfaces of their particles. Examples of such fungi- cides are sulfur and Bordeaux. Furfural, beta naphthol and copper soaps do not seem to ha\e this reaction of adsorption, neither do they reduce larvicidal efficiency as do the more bulky materials. In this study there was no fungicidal material tested thatj could be included in an emulsion in suffi-l cient quantity to be toxic to the fungi of ' apple scab, lentiirin iiitierjiuilis (Cke.) Wint., or apple bitter-rot, Phyllosticta soli- taria Ell. & Ev., under field conditions. The commercial white oils include two of the most successful summer-oil emul- sions. The laboratory efficiency of these oils was 24, 32 and 53 per cent, with an a\erage of 36.3 per cent, Table 6, item 9. Stock oil 5, fig. 3, with the highest efficiency Noxember 1936 farrar: effect of petroleum-oil sprays 15 —53 per cent— lias 15.6 per cent inure oil, smaller oil droplets and better wetting properties than the other two emulsions. Stock 200, fig. 2, is uniform phjsically but has low wetting power. Stock 7 is one with poor physical properties, including poor wetting, irregular oil droplets and low sta- bility. Jhe results obtained with these com- mercial white oils show that they are typical of results that may be obtained with an>' satisfactory white-oil emulsion. The variations used in experimental emulsions were not sufficient to show marked superi- ority over the standard emulsions. The physical changes made in emulsions, Table 6 and fig. 4, express about the physical limits possible with strictly white-oil emul- sions for use in tree sprays applied to foli- age. White-oil Emulsions plus Pyrethrum Pyrethrum extracts, 1—3 pounds per gal- lon of oil, combined with the oil phase of emulsions, produced the most efficient cod- ling moth larvicides. Ten formulae con- taining pyrethrum gave an average relati\e efficiency of 87.8 per cent. The consistent superiority of pyrethrum emulsions is shown in fig. 4, item 13. Addition of fungicides to pyrethrum emulsions reduced a\erage efficiency of the latter 21 per cent. Furfural and beta naph- thol did not reduce the kill as greatly as did copper soap, furfuramide, copper Bor- deaux or sulfur, Table 6, item 4, fig. 4, item 1 1. White-oil Emulsions plus Nicotine Oil emulsions with nicotine produced the second most efficient codling moth spray. Table 6, item 2. The seven formulae tested averaged 10 per cent less efficient than the pyrethrum sprays, although the range in control shown b\' the oil—nicotine sprays is greater than that of pyrethrum sprays, fig. 4, item 14. All sprays of oil emulsion with nicotine were more efficient than white-oil emulsions alone. The use of oil emulsion- nicotine sprays in the field has shown the residue to be as toxic and nearh as persis- tent for codling moth larvae under field conditions as that of lead arsenate. Oil emulsions containing nicotine are the only mixtures of oil and a plant poison that have withstood exposure to weather approxi- mately as well as lead arsenate. White-oil Emulsions plus Derris Derris extracts act more slowly and are more stable to oxidation than are pyreth- rum extracts. It was with the hope of finding a more stable insecticide than pyr- ethrum that derris was tried extensively in laboratory and field tests. The results of tliese tests were disappointing. In many cases emulsions containing derris were in- ferior to those containing pyrethrum. The efficiency of derris. Table b, item 5, fig. 4, item 12, is shown to be widely distributed, illustrating the very erratic results obtained with this material. The derris sprays tested are not a dependable group when incor- porated with white-oil emulsions for kill- ing codling moth larvae. White-oil Emulsions plus Other Insecticides Fluosilicates at 10 per cent mixed with oil emulsions are more toxic than white oils alone, but such combinations have very un- desirable properties which do not make them practical mixtures. Table 6, item 7, fig. 4, item 7. In the miscellaneous group III, Table 6, item 3, is a substance called petroleum nitrogenous base. The nitrogenous bases used in the tests have a boiling range be- tween 180 and 520" F. This is the only material other than the extracts of the plant poisons which offered promise as an insec- ticide with oil. The other materials listed under the miscellaneous groups I and II do not show sufficient promise to justify further study. The materials included in the miscellaneous groups are not all chemi- calh related, which makes the grouping artificial. Laboratory Tests with Lead Arsenate IWi) pounds ot lead arsenate plus 4 pounds of hydrated lime killed codling moth larvae in the laborator\- as efficiently as this spray did in the field. It is of inter- est to note that with the most uniform coat- ing obtainable with lead arsenate on apples, the efficiency of this spray over unspra\ed apples was only 36.3 per cent. This means that relati\ely 63.7 per cent of the larvae penetrated a coating of lead arsenate and gained entrance to the fruit. The highest control with lead arsenate was 88 per cent, or identical in control with the average efficienc\' for the p\rethrum-impregnated emulsions. Table 6 and fig. 4, item 10. 16 ILLINOIS NATURAL HISTORY SURVEY BULLETIN Vol. 21, Art. 1 Red Spider Tetranychus sp. The most satisfactory control of red spider was obtained by the use of a technical white-oil emulsion at a con- centration of 1 per cent. ON CONIFKRS Conifers are often attacked by red spi- ders to such an extent that the younger trees are killed. Where the mites are not sufficiently abundant to kill the trees, they so destroy the chlorophyll in the tissues that the trees appear brown. Many of the needles become dry and drop off, leaving the tree very unsightly. than in a film, as is commercial oil stock 5. This irregular type of coating reduces the danger of injury to foliage and leaves the oil spots scattered over the surface to en- tangle the red spiders as they crawl about the needles. Immediate kill of red spider by oil stock 200 is not apparent, but its residual effect gives the most satisfactory control of any emulsion tested. Addition of a material to give this oil emulsion higher wetting properties did not cause foliage injury but did reduce protection afforded against red spider. In two cases oil stock 6990 gave very Table 7.—Degree of safety and red spider control for oil emulsions on the foliage of conifers. Oil Formula Item No. November lQ3b FARRAR: EFFECT OF PETROLE U M -Ol L SPRAYS 17 The technical white oils, properl}- emulsi- fied, may be applied with relative safety at any time of the year except in extremely hot weather. Care should be taken in ap- plying oil sprays to blue spruce, compact arbor vitae and all new plantings. Drench- ing of conifer foliage with oil sprays should be avoided. Pines and junipers will toler- ate one or more applications of 1—2 per cent oil emulsion ; spruce, arbor vitae and similar tender species from one-half to 1 per cent oil emulsion. One, or at most two, applications of the proper oil emulsion have given excellent protection for the season against the common red spiders attacking evergreens. ON RASPBERRIES Oil emulsions have been tested on rasp- berries for two seasons. In these tests one mite, Phyllocoptee oleivorus Ashm., by the use of oil sprays. San Jose Scale Aspidiolus perniiiosHs Com. For control of San Jose scale, the most efficient emul- sions contained relatively large oil droplets associated with high wetting and quick breaking properties. Oil emulsions have been used against scale since about 1878. Because of the wide distribution of San Jose scale it has received much attention in the development of control measures. Great impetus was given to the study of oil emulsions for this insect following the complete destruction of many orchards by this scale from 1919 to 1922, according to Ackerman (1923), Davis (1924) and Chandler, Flint & Huber (1926). Fig. S.—Soluble oil 16. X490. to three applications of stock oil 200 at 1 per cent concentration gave excellent con- trol of red spider without injury to the foli- age. The sprays were applied with a power sprayer at a pressure of 200 pounds. For satisfactory results it was necessary to use care to wet tlie under surfaces of all leaves. For this purpose a short rod carrying three fine nozzles turned upward permitted ex- cellent spraying from the underside. Stock oils 5220 and 5230 did not injure the foli- age but failed to control the mites. The low viscosity of these oils, 40 and 60 seconds respectively, would suggest that they pene- trated the tissues readily and did not leave a persistent oil film to entangle the crawl- ing spiders. Favorable results with oils on red spi- der are reported by Vinal (1917) on cucumbers, by Newcomer& Yothers ( 1 927 ) on fruit trees, by Whitcomb & Guba (1928) on cucumbers, and by Compton (1931) on greenhouse crops. Yothers &: M^ison (1930) had unfavorable results in controlling the egg stage of the citrus rust Fig. 6.—Soluble oil 90. X490. The scale affords such natural protec- tion that any insecticide to be effective must gain access to the living insect. Abil- ity of oil sprays to form films or coatings that are toxic to scale has made oil emul- sions a reliable source of control. The work done in the control of tiiis insect lias demonstrated the physical and chemical properties necessary in an emulsion for high efficiency against a number of insects other than scale. According to Ackerman (1923) and Davis, Yothers, Ackerman & Haseman (1926, 1927), most workers find that at least a 2 per cent actual oil is required to give satisfactory control of scale. The proper concentration will depend entirely on the properties of the emulsion, as is shown in Table 8. The data were calcu- lated according to the formula of Abbott (1925). Abbott (1926) found that mor- tality counts on San Jose scale made 30 days after the treatment by sprays gave accurate indices of performances. In these tests the mortalit\' counts were made from ILLINOIS NATURAL HISTORY SURVEY BULLETIN \'ol. 21, Art. four to six weeks after the oil-spray treat- ments were applied. Soluble oils 16, fig. 5, and 90, fig. 6, con- tain the same amount of emulsifier, but oil 16 contains a highly saturated white oil. This emulsion is less stable than the emul- sion containing the unsaturated oil. The effect of saturation on the stability of solu- ble oil 16 is reflected in the difference be- tween these two emulsions in the mortality in this comparison between soluble oils 47, 48 and 49. All are less stable than the 83- second-viscosity emulsions even though the lighter emulsions contain the emulsifier in greater quantity. deOng 5; Knight (1925) found as they decreased the amount of soap emulsifier used in relation to the volume of oil that "the results showed a progressive increase of kill as the amount of soap was decreased, Table 8.—Relation between viscosity, saturation, ratio of emulsifier, and droplet size, for miscible-oil sprays tested on San Jose scale. Oil Formula Oil- droplet No. Tests Per Cent Item No. Composition* Size Concentration*!* Ratio of Emul- Vis- Satu- Emul- sitier cosily ration sifier to Oil microns 1. I J .' . .'.5 J. Relative Efficiency at Per Cent Concentration Soluble November l''3fa farrar: effect of petroleum-oil sprays 19 It is evident from these data that effici- ency is influenced b\ viscosity, saturation and oil-droplet size. These variations give to an emulsion certain properties that in with their respective degrees of control, are shown in Table 9. Certain relationships are lacking but those most influential in control of scale are included. Soluble oils ^"f^^--p'pm'>^ t c Fig. 9.—Soluble oil 22. X490. Table 9.—Relation between viscosity, saturation, ratio of emulsifier and oil-droplet size for commercial oil sprays tested against San Jose scale. Fig. 7. 20 ILLINOIS NATURAL HISTORY SURVEY BULLETIN \'ol. 2 1 , Art . containing a 350-second oil. The oil-drop- let size is not greatly different in these two emulsions. Soluble oil 17 has a lower ratio of emulsifier to the oil than the other solu- Fig. H.-^C ble oils and is a quicker-breaking emulsion. This oil is consistently superior to the others in its control of scale. Boiled fish-oil soap emulsions, fig. 12, were as efficient against San Jose scale as was soluble oil 17. Both of the boiled emul- sions, Table 9, items 4 and 5, have larger oil droplets and somewhat quicker break- ing qualities than soluble oil 17. The gov- ernment formula'^ contains half as much soap emulsifier and considerably more water than the Illinois formula^. This con- dition imparts to the government formula a slightly larger oil-droplet size and quicker breaking qualities. There are certain sections in Illinois orchard areas where the extremely hard water will prevent this formula from emul- sifying properly. For this reason the Illinois formula is recommended and used. This emulsion contains sufficient soap to permit emulsification in most Illinois waters. Both of these emulsions contain about one third Fig. 12.— Boiled fish-oil soip miiilsioii stock, Illinois formula. X490. = Government formula: Potash fisli-oil soap 1 pound Water 2 quarts Lig:ht-gTade lubricating oil 1 gallon Illinois formula; Potash flsh-oil soap 1-2 pounds "Water 1 quart Light-grade lubricating oil 1 gallon of their volume in water and soap and arc therefore recommended for use at a con- centration of 3 per cent, which places them about on a basis of comparison with a solu- ble oil at 2 per cent concentration. When boiled-soap emulsions are tested and com- pared with miscible oils on their oil basis they are as effective in their kill of scale as the soluble oils. This accords with find- ings of Ackerman (1923), Davis (1924), Chandler, Flint & Huber (1926), English (1928) and Swingle & Snapp (1931). Stock emulsions 5 and 8, Table 9, items b and 7, are emulsions containing inert cmulsifiers. In both, the ratio of emulsifier to the oil is sufficiently low to impart quick- MODERATE ^H 2>i OIL Cn 6K LIME 1777} 2% 0IL,6"< LIME SULFUR I Fig. 13.— I-lelation in days between bud de- velopment of apple and safety to the tree when sprayed with a 2 per cent soluble-oil emulsion, 6 per cent liquid lime sulfur, or a combination of both. The first spray was applied in the following periods of tree development: dormant, tip-green, delayed-dormant, and cluster-bud. breaking properties, as shown by their respective oil-droplet size. The control of San Jose scale exhibited by these emulsions is comparable with the quick-breaking solu- ble oils and boiled fish-oil soap emulsions. Factors other than insecticidal efficiency have entered into public acceptance of the] several commercial emulsions. Many of those who have made and used the boiled fish-oil soap emulsions will continue to do so, but there is an increasing trend toward, the commercially prepared quick-breakingj soluble oils. This has come about from the} relatively low cost of soluble oils, the easel with which they can be stored and diluted, and the uniform performance given by such oils as soluble oil 17 in the control of San Jose scale. November 19^6 farrar: effect of petroleum-oil sprays 21 Delayed-dormant Applications of Oil Sprays For a number of years there has been a tendency to delay the application of oil sprays for the control of San Jose scale as late as possible in the season in order to kill such aphids as were hatched. Very few cases of injury are reported from stable oil sprays applied when the trees are strictly dormant. Felt (1913) reported less in- jury when oils were applied just before growth started in the spring than in fall applications. deOng (1926) observed that the blooming date was influenced by the season of application, recording that the have been obtained. In the test are included an unsaturated miscible oil at 2 per cent, applied in the fall, winter and spring dor- mant, and the delayed-dormant stages ; boiled fish-oil soap emulsion at 3 per cent : and the miscible oil at 8 per cent concen- tration. The last two are applied in the spring dormant. In one year the fish-oil soap emulsion, and for three years the 8 per cent miscible oil, have shown a retarding effect on leaf de\elopment. In all cases the retardation was no longer noticeable six weeks after the buds started to open. There have been no injurious effects on an\' of Table 10.—Relation between oil-droplet size of a miscible oil and its insecticidal efficiency as tested against aphids.* Ratio of Soap to Oil No. OF Tests (1000 .\PHIDS) AT Per Cent CONXENTRATION Relative Efficiency at Per Cent Concentration 1 22 ILLINOIS NATURAL HISTORY SURVEY BULLETIN 21, Alt. unc witli the fircatcf \\cttiiig; abilit\- is tlic more cftcctixc on aphids. " Griffin, Richardson c^ Hurdcttc (1927) found tliat "under conditions of compar- able concentrations and type of oil, misciblc Fig. 14.—SoluMe oil 18. X490 breaking emulsion and a higher mortality of aphids. In soluble oil 17, (ig. 10, the emulsifier has been reduced over that of soluble oil "^O \\ith a still greater efficiency against aphids. I'liis oil exemplifies about the maximum killing power obtainable with a miscible oil that is sufficiently stable to be marketed commercially. In all of the tests the toxicity to aphids is greater at the lower concentrations of the emul- sions or the emulsifier. This condition illustrates the principle that excess wetting causes a run-off of the spray material and a reduction in the kill of some contact in- secticides. Table 1 1 includes the results obtained Table 11. -Relation between droplet size and insecticidal efficiency of commercial oils tested against aphids.* Com- mercial Item Oil No. Oil- droplet Size No. OF Tests (1000 Aphids) at Per Cent Concentration Relative Efficiency at Per Cent Concentration 1 ^ovemtier lQ3b FARRAR: EFFECT OF PETROLE U M -Ol L SPRAYS 23 and stability of each emulsion determine to a large extent these factors. The effect of the wetting properties of emulsions on their efficiency can be illustrated by comparing stock oils 5 and 4. Stock oil 5. Table 11, item 1, and fig. 3, contains an inert emul- sifier and has quick breaking properties. It is less effective than stock oil 4, which con- tains a soap emulsifier and has higher wet- ting and quicker breaking properties. Soluble oil 17 combines the property of higher wetting than that possessed by the former emulsions with almost as good breaking properties. This oil, however. dilute emulsion for increasing its toxicity against aphids but soap is not compatible with the stock emulsion when incorporated with it as a concentrate. Free nicotine is compatible with this emulsion in the concentrate when used in proportions of not more than 1 per cent. Such a combination makes an emulsion that is very efficient against aphids. When one- fourth of 1 per cent of soap is added to the dilute emulsion to give it increased wetting, as in item 6, the mortality of aphids is higher than that given by the emulsion without soap but containing twice the Table 12.—Laboratory tests on aphids with gum emulsions, demonstrating the necessity for increasing wetting power or for incorporating nicotine into gum emulsions to control aphids. ITE.M 24 ILLINOIS NATURAL HISTORY SURVEY BULLETIN Vol. 21, Art. 1 Nicotine, added to either the stock emul- sion or the diluted spray, was the only really efficient spray for aphids. These tests demonstrate the toxic nature of nicotine to aphids. Experiments were conducted with 25 different oil emulsions, most of which were tested at 5, 8 and 10 per cent concentra- tions. The results are shown in Table 13. These experiments demonstrate clearly Table 13.—Results of laboratory tests with various concentrations of oil emulsions on eggs of oyster-shell scale. Item November 193b farrar: effect of petroleum-oil sprays 25 oil sprays. The results of field trials are shown in Table 14. Young oyster-shell scale hatch at a season of the year (May- July) when their host plant is in full foli- age. Although practically any oil applied at 2 per cent concentration will give con- trol of this scale, the oil selected for ap- plication should be safe to apply on foliage. The white-oil emulsions marketed as sum- mer oils have proved the most satisfactory. similar to soluble oil 17, at 5 per cent con- centration, have been tested against this pest. This oil has given a verj- high degree of control where good wetting is obtained and when the oil is applied in the spring before the elm foliage appears. The control of young European elm scale by summer-oil sprays has not been as satisfactory because of the wide distribu- tion of the young over the leaves. To obtain Table 15.—Results of leaf roller ovicide tests in the laboratory at three concentrations of emulsions. Each egg mass averaged 57 viable eggs. Formula Item No. 26 ILLINOIS NATURAL HISTORY SURVEY BULLETIN \'()1. 21, Art. 1 tion gave excellent control of hatching scale when 4 pounds of 30 per cent potassium fish-oil soap were added to each 100 gal- lons of dilute emulsion. He found the addi- tion of soap necessary in order to secure adequate wetting of the foliage and insects. No injury resulted from his sprays on American and Cornish elms, applied July 15 at Monroe, Mich. Fruit-tree Leaf Roller Archips argyrospila \\'alk. Stability was the dominant physical property of an emulsion that was efficient in killing eggs of the fruit- tree leaf roller. The less stable emulsions were the most efficient. The control of fruit-tree leaf roller b)' the application of lead arsenate sprays has not given uniformly satisfactory results, Fig. 16.—.Soluble oil 8350. X490. according to Regan (1923), Wakeland (1925), Flint & Bigger (1926) and Har- man (1928). Feeding of the larvae can be checked with lead arsenate sprays, but special sprays using high dosages of lead arsenate are necessary. Authors agree that the logical method of control is one directed against the egg stage of the insect. Oil emulsions have given the most satis- factory control of leaf roller eggs in the laboratory and in the field. Wide varia- tions have been found to exist between the various oil emulsions tested. Under field conditions it is seldom that sprays can be applied thoroughly enough to strike every egg mass on the tree. For this reason field trials of the same oils and concentrations have not given so high a mortality as have laboratory tests. This is in accord with the findings of Penny (1921). Comparable results were obtained in field tests (not included in this paper) where the oil sprays listed in Table 15, items 1, 5, 6, 7 and 12 were given field trials. Regan (1923) asserts that unless 75 per cent of the eggs can be killed the expense of the spray is not warranted. Experiments of Flint & Bigger (1926), Harman ( 1928), ToUes ( 1931 ), and Par- rott, Hartzell, Glasgow & Harman ( 1931 ) show that less than 6—8 per cent actual oil in an emulsion will not give control of leaf roller eggs. These tests further indicate that the quicker-breaking emulsions will kill the pggs at a lower concentration than the slow-breaking emulsions. The cold- mixed Bordeaux or Kayso emulsions have been the most efficient because of their quick-breaking properties. Laboratory data on leaf roller eggs given in Table 15, items 1 and 2, illustrate the superior killing power of cold-mi.xed emul- sions. With an actual oil content of 4 per cent, the 4:4:50 Bordeaux and calcium caseinate emulsions gave 100 per cent kill of eggs. Commercial soluble oil 7 is the only soluble oil giving complete kill at a low concentration. The non-miscible prop- erties of this oil in hard water would not make it a practical commercial emulsion for other than leaf roller or similar insect control. Only a small portion of this emul- sion would remain in suspension without constant agitation. Boiled fish-oil soap emulsion, item 4, with a large oil-droplet size and quick-breaking property, gave al- most as high mortality of eggs as did the oils under items 1, 2 and 3. Soluble oil 8350, item 5 and fig. 16, has the same emulsifier ratio as soluble oil 17, item 12, but contains a 225-second-viscosity oil. The higher-viscosity oil produces an emulsion that does not disperse as readily as does oil 17. As a result the diluted solu- ble oil 8350 tends to separate out of the water phase, giving to the emulsion a quick- breaking property. The same characteris- tic is exhibited to an even greater extent by commercial soluble oil 7. Neither oil has sufficient emulsifier to disperse the oil particles completely when diluted with hard water. Emulsions included in items 6 to 1 1 var\' in certain ingredients from soluble oil 17. Ihe cresylic acid in soluble oil 5110 and extra emulsifier in soluble oil 22 did not increase the toxicity materially. The addi- tion of 1 per cent free nicotine as in oil 8360, fig. 17, nicotine sulfate at 1 :800, or petroleum base, as in oil 8370, fig. 18, did not increase the kill over that exhibited bv Ni li).50 FARRAR: EFFECT OF PETROLE U M -Ol L SPRAYS 27 soluble oil 17. In all of the experiments the quick-breaking soluble oils tested at 8 per cent concentration gave a satisfactory con- trol of leaf roller eggs. This is significant because of the wide use of soluble oils com- mercially for the control of this insect. As ovicides for leaf roller eggs, emulsions with, large oil droplets, such as occur in cold-mi.\ed emulsions, are more efficient than commercially prepared emulsions when compared at equal concentrations. Certain quick-breaking soluble oils will give a commercial control of leaf roller if they are carefully applied at a concentra- tion of 8 per cent or greater. The viscosity 'stm'^if^^W^J^ will cover the a\erage farmstead. One application is sufficient for light infesta- tions but two or three treatments at inter- vals of two weeks are recommended in heavily infested areas. OILS WITH FUNGICIDES Dormant-oil emulsions can be used with sulfur fungi- cides in the dormant stage of tree development. If used after the buds start to swell, serious injury may result. There is danger of injury if oil emulsions are applied in the delayed-dormant stage of tree development, par- ticularly when sulfur is to be used in the later sprays for the control of fungous diseases. It is doubtful whether fungicides of the more common types can be used with summer emulsions without dis- turbing the efficiency of the emulsion or causing injury to the plant tissue when they are applied to foliage. sHM 'V^ *',' /'-r«- XXr^ Fig. 17. Fig. 18. - Soluble oil 8370. X490. of oils between 83 and 350 seconds is not of major importance except as it affects the breaking property of the emulsion. A solu- ble oil containing an oil of 47 seconds fif \iscosity was not efficient against the eggs of the fruit-tree leaf roller. Fleas Pii/ex inilaiis Linn. Oil emulsions at a concentration of 5 per cent gave excellent control of fleas on farmsteads. The economic importance of fleas as .1 pest of rural communities is not generally recognized nor appreciated. The author made a survey of several counties in central Illinois and found a large number of farm- steads infested with fleas. Reports from farm advisers located in other counties in- dicated that similar conditions were present over a large section of the state. Tests carried on over a period of three years indicate that soluble oil 17 at 5 per cent concentration will give a satisfactor\ control of fleas. Premises (interiors of barns, outbuildings, etc.) must be thoroughly cleaned of litter, dust and other refuse. The area is then sprayed with a 5 per cent oil emulsion and the floors thoroughly soaked. From 300 to 800 gallons of dilute spra\ Dormant Oils with Fungicides Under some conditions it is practical to use sprats that contain an emulsion and .1 fungicide. The most cotnmon fungicides contain either copper or sulfur. Dormant peach and apple trees will withstand rela- tively high concentrations of either oil einulsion or lime sulfur without injury. It is therefore possible to spray dormant trees with oil emulsions mixed with some fungi- cides. Such sprays are ver\- useful in the control of scale and peach-leaf curl on IH'ach, and scale and apple scab on apple. The properties of such sprays will depend on the fungicide added. The use of copper in the form of Bor- deaux has been widely tested and has proved successful in most respects. Emulsions con- taining soap can be added to Bordeaux it the concentration of the uncombined copper or calcium is not so high as to re\erse the type of emulsion. Most soap emulsions flocculate in the presence of inert forms of sulfur. "Flota- tion," a t\pe of ver>- finely divided precip- itated sulfur obtained in the manufac- tured-gas industr> from a process known as h'quid purification, combines with an inert 28 ILLINOIS NATURAL HISTORY SURVEY BULLETIN \'ol. 21, Art. 1 emulsified oil, such as oil 210, to make an oil—sulfur combination possessing unusual properties, figs. 19, 20. These properties are described by Farrar & Smith (1930). Emulsions made with extremel\ stable cmulsifiers, as oil 210, will mix with lime sulfur without separation. Such sprays can be used on dormant trees without notice- able injur)'. The addition of sulfur to emulsions, par- ticularly in the form of lime sulfur, has many objectionable features, the most seri- ous of which is separation of the emulsion in the presence of lime sulfur. All miscible oils and stock emulsions that contain soap as the emulsifier will not mix with lime sulfur without separation of the emulsion and the liberation of free oil in the spray the tip-green stage,'' the emulsion alone did not injure, but lime sulfur either alone or mixed with oil emulsion caused very notice- able injury. In the delayed-dormant period, when the leaves were beginning to unfold, all of the sprays produced some injury. Least injury occurred on the oil emulsion- sprayed trees; those receiving lime sulfur were badly burned, and those receiving the mixture of oil and lime sulfur were so severely burned that the leaves did not develop further. The oil emulsion sprayed in the cluster-bud stage resulted in very noticeable injury to the unfolding leaves and flower clusters. Dutton (1932) finds that "there is evidence that the presence of oil with lime sulfur renders lime sulfur injury more severe or causes its develop- ..O & Fig. 10. Oil siotk 210 4''(l, Fig. 20. -Oil stock 210 plus sulfur. X490. mixture. This finding is in accord with the results of Ackerman (1923) and Yothers & Winston (1924). It is dangerous prac- tice to apply partly separated emulsions to trees even in the dormant stages of their development. Yothers & Winston (1924) suggest the addition of stabilizers to oil- lime sulfur mixtures. Cutright (1929) describes the 10 oil—fungicide combinations which he thought possible to use under Ohio conditions. deOng (1930) suggests the use of organic sulfur in the cyclic series with oil emulsions to increase their fungi- cidal value. The results of two years of tests with sprays containing lime sulfur and oil emul- sion are shown in fig. 13. In these experi- ments three distinct types of emulsions were tested—a miscible oil at 2 per cent concen- tration, a proprietary emulsion recom- mended for use with lime sulfur, and stock 210. All were applied in the dormant, tip- green, and delayed-dormant stages of tree development. No injury from any of the materials was apparent among those trees sprayed while dormant. With the trees in ment when lime sulfur without oil would not produce injury." Although sometimes recommended, the spraying of fruit trees \vith oil emulsion and lime sulfur is not a safe practice. In many sections spray schedules on apples call for a spray of lime sulfur ver\' early in the season, for the control of apple scab. This spray is often applied in the cluster-bud stage of development. Figure 13 shows the effect of oil emulsion and liine sulfur on foliage. Serous burning will usually result. The same condition can be approached where the oil spray is delayed and followed soon after by an application of summer-strength lime sulfur. Figure 21 summarizes the experiments to determine the interval of time that should eLapse be- tween the oil spray and a spray of lime sulfur. It appears to be relativelj- safe to apply lime sulfur two weeks after an appli- cation of oil emulsion. " The tip-green stage of buel development is the time at which the bud scales have parted sufficiently to show the new green tissue that has been developing within the expanding bud. This stage precedes by a few days the rapid expansion of new leaves. November 1430 farrar: effect of petroleum-oil sprays 29 Yothers & Mason (1930) found that two or three weeks should elapse before an oil spray on citrus was followed by a sulfur spray or dust for the control of citrus rust mite. Overholser 5: Overley (1930) found imder Washington conditions that oil sprays previous to Jul\' 1 caused injury to fruit and foliage following a delayed-dor- mant application of lime sulfur. Summer Oils with Fungicides The need of an oil emulsion with fungi- cidal properties has been recognized. Many attempts ha\e been made to combine sulfur, moderate: 1 I Fig. 21.—The incompatibility of dormant-oil spray and sulfur makes necessary an interval of 10 days to two weeks between applications ot the two mixtures. The graph shows the in- jury to the tree caused by applying a dormant oil too late in the season; that is, just before the cluster-bud stage. I copper and their derivatives with both suni- I mer and dormant-oil emulsions. Other \ materials that have exhibited fungicidal properties have been tested but most of \ them have been discarded as unsatisfactory ! Although sulfur is widely used as a fungi- cide, it will produce injury even when used in small quantities with oil, according to deOng (1928c). Hoerner (1929) sug- I gests that Penetrol is compatible with flo\v- ijers of sulfur and safe on apple foliage if !| the two are mixed with water before thc\ I are combined. Talbert & Swartwout 1(1931) state, "Lubricating-oil emulsions (I have been used throughout the summer in [applying the regular summer combination applications, using the oil at 1 per cent and 2 per cent with the standard insecticidal and fungicidal spray, lime sulfur and Bor- deaux with lead arsenate." This finding is not in accord with tlie general knowledge of sulfur and oil com- binations. Oil emulsions containing cer- tain forms of copper are relatively safe on foliage but the spray has low insecticidal efficiency and it is difficult to store because of its corrosive action on metal. Oil emul- sions may be added to well-made Bordeaux without danger of injury but the Bordeaux reduces the efficiency of the oil emulsion, according to Porter & Sazama (1930). Oil emulsions containing derivatives of furfural show promise but are not com- pletely satisfactory as insecticides or fungi- cides. To our present knowledge there is no material sufficiently toxic to fungi that can be added to an oil emulsion without inter- fering with either the insecticidal efficiency of the oil emulsion or with the toxicit\' of the fungicide to fungi. The reduced effi- ciency of emulsions with fungicides was demonstrated in experiments with codling moth larvae, Table 6 and fig. 4. In these experiments, fungicides added to the p\i- ethrum sprays reduced their average effi- ciency from 88 to 66 per cent, and that of the white oils without pyrethrum from 3-1 to 33 per cent. Fungicides that were par- tially soluble in the oil phase of the emul- sion decreased efficiency of the sprays les.^ than did the fiocculent materials, such as flowers i)f sulfur or Bordeaux. BIBI.TOGRAPY Abbott, W. S. 1925 .\ method of computing the effective- ness of^ an insecticide. Jour F.con Fnt 18(2):26.';-7. Ap 1926 Determining the effectiveness of dormant treatments against the San Jose scale. Tour F.con Ent 19(6): 858-60. D Ackerman, A. J. I92J Preliminary report on control of San Jose scale with lubricating-oil emul- sion. USDA Circ 263. 18pp. Ja Burroughs, A. M. 1924 Effects of oil sprays on fruit trees. Am Soc Hort Science Proc 20:269-77. Bibliog. Chandler, S. C, \V. P. Flint & L. L. Hubcr 1926 Recent insecticide experiments in Illinois with lubricating-oil emulsions. Ill Nat Hist Surv Bul 16(2):103- 26. 2figs. My 30 ILLINOIS NATURAL HISTORY SURVEY BULLETIN ;i, Art. 1 Cleveland, C. R. 1931 An experiment with summer oil for the control of the European elm scale, Gossvpiiria ulmi L. Jour Econ Ent 24(2'):349-55. Ap Compton, C. C. 1931 Red spider control in greenhouses. Jour Econ Ent 24(5):1094-7. O Cook, A. J. 1881 New insect enemies and new methods of insect warfare. Mich Hort Soc Rep 10:133-8. Cutright, C. R. 1929 Combination insecticide and fungi- cide sprays for dormant and delayed- dormant spraying in Ohio. Ohio Ag Exp Sta Bimonth Bui 137(14:2): 42-4. Mr-Ap Davis, J. J. 1924 Comparative tests with dormant sprays for San Jose scale control. Jour Econ Ent 17(2):285-9. Ap Davis, J. J., W. W. Yothers, A. J. Ackerman & L. Haseman 1926 Report on oil emulsions. Jour Ficon Ent 19(2):407-11. Ap 1927 Report on oil emulsions. Jour Econ Ent 20(1) :229-35. F deOng, E. R. 1926 Technical aspects of petroleum oils and oil sprays. Jour Econ Ent 19 (5):733-45. O 1928a Petroleum oil as a carrier for insecti- cides and as a plant stimulant. Indus & Eng Chem 20(8):826-7. Au 1928b Progress report on the use of pe- troleum oil as an insecticidal spray. Jour Econ Ent 21(4):525-9. Au 1928c Specifications for petroleum oils to be used on plants. Jour Econ Ent 21 (5j:697-702. O 1929 The characteristics and uses of pe- troleum-oil sprays. 4th Int Cong Ent 2:145-54. Ifig. D 1930 Selection of petroleum oil for spray- ing purposes. Indus & Eng Chem 22 (8):836-9. Bibliog. Au 1931 Present trend of oil sprays. Jour Econ Ent 24(5):978-85. O deOng, E. R. & Hugh Knight 1925 Emulsifying agents as an inhibiting factor in oil spravs. Jour Econ Ent 18(2) :424. Ap deOng, E. R., Hugh Knight & Joseph C. Chamberlin 1927 .A preliminary study ot petroleum oil as an insecticide for citrus trees. Hilg 2(9):351-84. 4figs, bibliog. Ja Dutton, W. C. 1932 Spray injury studies. 1. Injuries trom summer applications on apples. Mich State Coll Ag Exp Sta Sp Bui 218. 68pp, 21figs, bibliog. Ja English, L. L. 1928 Some properties ot oil emulsions in- fluencing insecticical efficiency. Ill Nat Hist Surv Bul 17(5):235-59. 8figs, bibliog. Mr Essig, E. O. 1931 .\ History of Entomology, pp406-23. Macmillan N Y. 1029pp, 263figs, index. Mr Farrar, M. D. 1929 Oil sprays for late-brood codling moth. Trans III State Hort Soc 63: 147-53. Ifig. D Farrar, M. D. & W. P. Flint 1930 Rearing codling moth laryae through- out the year, Carpocapsa pomonelta I.. Jour Econ Ent 23(l):41-4. F Farrar, M. D. & M. A. Smith 1930 Some physical properties of certain dormant-oil emulsion-sultur combi- nations. Jour Econ Ent 23(6) :979- 84. 2pls, bibliog. D Felt, E. P. 1913 Injuries following the application ot petroleum or petroleum products to dormant trees. Jour Econ Ent 6 (2):160-1. Ap Flint, W. P. 1930 Orchard insect conditions during 1930 and the outlook for 1931. Trans 111 State Hort Soc 64:261-76. 4charts. D Flint, W. P. & J. H. Bigger 1926 The fruit-tree leaf roller and its con- trol under Illinois conditions. Ill Nat Hist SuRy Circ 16. 12pp, 4figs. Jl Flint, W. P. & M. D. Farrar 1931 Progress in orchard insect control for 1931. Trans III State Hort Soc 65: 148-70. 7charts. D Ginsburg, Joseph M. 1929 A correlation between oil sprays and chlorophyll content of foliage. Jour Econ Ent 22(2):360-5. Ap 1931a Penetration of petroleum oils into plant tissues. Jour Ag Res 43(5): 469-74. S 1 1931b What summer-oil sprays may do to apple trees. Jour Econ Ent 24(1): 283-90. 2figs.", bibliog. F November 1936 farrar: effect of petroleum-oil sprays 31 Gray, G. P. & E. R. deOng 1926 California petroleum insecticides. Laboratory and field tests. Indus ix Eng Chem 18(2):17S-80. F Green, E. L. 1927 Lubricating oils as insecticides in dormant spraying. Indus & F'.no; Chem 19(8):931-5. 3figs. Au Griffin, Edward L., Charles H. Richardson & Robert C. Bnrdette 1927 Relation of size of oil drops to toxicity of petroleum-oil emulsions to aphids. Jour Ag Res 34(8):727-38. 2figs, bibliog. Ap 15 Harman, S. W. 1928 The fruit-tree leaf roller in western New York. N Y State Ag Exp Sta Bui S61:13-ff. 31pp. 6figs, bibliog. D Headlee, T. J. 1932 The problem of codling moth control. Jour Econ Ent 25(3):545-54. Je Headlee, Thomas J., Joseph M. Ginsburg & Robert S. Filmer 19!0 Some substitutes for arsenic in control of codling moth. Jour Econ Ent 23 (l):45-53. F Herbert, Frank B. 1924 Spray stimulation. Jour Econ Ent 17(S):S67-72. 2 figs. O 1931 History of the oil and nicotine com- bination. Jour Econ Ent 24(5); 991-7. Bibliog. O Herbert, F. B. & M. D. Leonard 1929 Observations on the oil-nicotine com- bination for the control of the codling moth and other apple insects in the Pacific northwest. Jour Econ Ent 22(l):72-8. F Hoerner, John L. 1929 A progress report on the testing of sulfonated oxidation products of pe- troleum for their insecticidal proper- ties. Univ Md Ag Exp Sta Bui 310; 449-65. Je Hurt, R. H. 1931 The waste sulfite material of paper mills as an adjuvant to certain oil spray materials. Va Polv Inst, Va Ag Exp Sta Bui 277. 10pp. F Kelley, Victor W. 1926 The efl^ect of oil sprays upon the trans- piration of some deciduous fruits. Am Soc Hort Science Proc 23:321-25. Bibliog. ,1930a A comparison of the transpiration rates of 21 deciduous fruit species. Univ 111 Ag Exp Sta Bui 341:95-116 2figs, bibliog. F 1930b Effect of certain hydrocarbon oils on respiration of foliage and dormant twigs of the apple. Univ 111 Ag Exp Sta Bui 348:371-406. llfigs, bibliog. Je 1930c Effect of certain hydrocarbon oils on the transpiration rate of some de- ciduous-tree fruits. Univ 111 Ag Exp Sta Bui 353:581-600. Bibliog. Au Knight, Hugh, Joseph C. Chamberlin & Charles D. Samuels 1929 On some limiting factors in the use of saturated petroleum oils as insecti- cides. Plant Physiol 4(3):299-321. 2figs, bibliog. Jl Lathrop, F. H. & R. F. Sazama 1932 A laboratory-field method for the study of the efficiency of codling moth sprays. Jour Econ Ent 25(1); 83-96. 2figs. F Leonard, M. D. 1930 Further experiments with nicotine- oil tor the control of the codling moth in the Pacific northwest. Jour Econ Ent 23 (l):61-75. Ifig. F Lodeman, E. G. 1913 Spraying of Plants, pp5-7. Macmil- lan N Y. 399pp, 92figs, index. [1896] Mason, A. Freeman 1928 Spraying, dusting and fumigating of plants, p6. Macmillan N Y. S39pp, 237 figs, index. My Newcomer, E. J. & M. A. Yothers 1927 Experiments for the control of the European red mite and other fruit- tree mites. USDA Tech Bui 25; 24-33. Sfigs. N 1932 Experiments with insecticides for codling moth control. USDA Tech Bui 281. 29pp, 4pls, 7figs, bibliog. !' Overholzer, E. L. & F. L. Overley 1930 Effect of oil sprays on apple irees. State Coll Wash Ag Exp St.i 40th Ann Rep. Bui 245:43. D Overley, F. L. & A. Spuler 1928 Effect of dormant and delayed- dormant application of oil sprays on apple trees. Am Soc Hort Science 25:325-8. D Parrott, P. J., F. Z Hartzell, Hugh Glasgow ^ S. W. Harman 1931 Hints on new spray procedvircs. Jour Fcon F.nt 24(l):297-.^02. Bibliog. 1 32 ILLINOIS NATURAL HISTORY SURVEY BULLETIN \'ol. 21, Art. 1 Penny, 1921 Porter, 1930 Regan, 1923 Donald D. The results of using certain oil sprays for the control of the fruit-tree leaf roller in the Pajaro valley, California. Jour Econ Ent 14(S):428-33. O B. A. & R. F. Sazama Influence of Bordeaux mixture on the efficiency of lubricating-oil emulsions in the control of San Jose scale. Jour Ag Res 40(8):755-66. 3figs, bibliog. Ap 15 W. S. The fruit-tree leaf roller in the Bitter Root valley. Univ Mont .Ag Exp Sta Bui 154:22-7. 56pp, 7figs, bibliog. F 1930 Results of insecticide tests for the control of codling moth and observa- tions on codling moth activity in the Yakima valley, Washington, season of 1929. Calif Spray-Chem Co, Berkeley. 16pp, copyr. My 15 Regan, W. S. & A. B. Davenport 1928 Some results of three years exper- ience seeking better control measures for the codling moth in the Vakima valley, Washington. Jour Econ Ent 21(2):330-8. Ap Richardson, Henry H. 1931 An insecticidal method for the esti- mation of kerosene extracts of pyr- ethrum. Crop Prot Dig (Bui SerJ 24 (32):97-104. 3figs. F Smith, Ralph H. 1929 Studies on spray-tank agitation in the use of oil sprays. Jour Econ Ent 22 (6):929-34. D 1930 A brief report of the tank-mixture method of using oil spray. Jour Econ Ent 23(2) :376-82. Ap 1931 Studies on the oil-depositing qualities of oil-spray mixtures. Jour Econ Ent 24(5):98S-91. Ipl. O Spuler, Anthony & Fred P. Dean 1930 New combination sprays for codling moth control. Jour Econ Ent 23 (1):53-61. 7figs. F State College of Washington Agricultural Ex- periment Station 1932 Spray recommendations tor codling moth control in Washington for 1932. State Coll Wash Ag Exp Sta Ext Bui 167. 7pp. Mr Swingle, H. S. & Oliver 1. Snapp 1931 Petroleum oils and oil emulsions as insecticides, and their use against the San Jose scale on peach trees in the south. USDA Tech Bui 253. 48pp, 2pls, bibliog. Jl Talbert, T. J. & M. G. Swartwout 1931 Spraying investigations. Univ Mo Coll .Ag, Ag Exp Sta Bui 301. 16pp, 4figs. Ap ToUes, C. S. 1931 Controlling the fruit-tree leaf roller, Archips argyrospila, with oil emul- sions. Jour Econ Ent 24(3):592-4. Je Vinal, Stuart C. 1917 The greenhouse red spider attacking cucumbers and methods for its con- trol. Mass Ag Exp Sta Bui 179: 166-9. 30pp, Ifig, bibliog. N Volck, W. H. 1903 Spraying with distillates. Univ Calif Coll .Ag, Ag Exp Sta Bui 153. 31pp, 4figs. Je Wakeland, Claude 1925 The fruit-tree leaf roller. Its control in southern Idaho by the use of oil- emulsion spravs. Univ Idaho .Ag Exp Sta Bui 137. Upp. Mr Webster, R. L. 1931 Trends in codling moth control in the Pacific northwest. Jour Econ Ent 24(3):672-6. Je Western Cooperative Oil Spray Project 1932 Suggestions for use of oil sprays in 1932. Better Fruit 26(8) :16-17. F Whitcomb, W. D. & E. F. Cuba 1928 Control of red spider and powdery mildew on greenhouse cucumbers. Mass Ag Exp Sta Bui 246:287. 14pp, Ipl, 3figs. O Woodworth, C. W. 1930 Petroleum insecticides. Jour Econ, Ent23(5):848-Sl. O " Yothers, W. W. 1913 The effects of oil insecticides on citrus trees and fruits. Jour Econ Ent 6 (2):161-4. Ap 1918 Spraying for the control of insects and mites attacking citrus trees in Florida, USDA Farm Bu! 933:34. Illus. Mr Yothers, W. W. & Arthur C. Mason 1930 The citrus rust mite and its control: USDA Tech Bui 176:37-54, figs 9, 10, Bibliog. Yothers, W. W. & J. R. Winston 1924 Mixing emulsified mineral lubricating oils with deep-well waters and lime sulfur solutions. USDA Dept Bui 1217. 5pp, bibliog. D 3