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Advances in Entomology C. H. RICHARDSON Iowa State College, A m e s , Iowa
Stomach Poisons
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NE of the most important recent events affecting the use of arsenical compounds for controlling insects on fruits and vegetables is the change in the official tolerances for arsenic and lead. Effective August 10, 1940, the Federal Security Agency (9) has ruled that the tolerance for lead shall be increased t o 0.05 grain Pb per pound of produce and that of arsenic to 0.025 grain As (as AS2O3) per pound. The fluorine tolerance remains unchanged as of 1938 at 0.02 grain F per pound. These tolerances are subject t o change if methods for evaluating the toxic effects of lead and arsenic on human beings are improved. Although this action may reduce somewhat the care necessary in applying sprays and dusts and in removing the residues, it will not halt the search for new insecticides less toxic to humans and more efficient than the compounds of lead, arsenic, and fluorine now in use. Several important papers have appeared during the year that bear on the toxicity of lead and arsenic in spray residues on fruits and vegetables (20, 97, 112, 147).
When lead arsenate is ingested with apples, apparently the fruit substance protects the body within limits against the absorption of harmful amounts of lead and arsenic. In man, lead arsenate is broken down completely, probably in the digestive tract, the lead being eliminated with the feces, while the arsenic passes into the urine. The lead content of materials generally consumed as food in the United States does not appear now to present a hazard to health. St. John et al. (148) and McCulloch and St. John (109) furnish information on the toxicity of lead arsenate to sheep and cattle. An important study of the hydrogen-ion concentration in relation to the toxicity of lead arsenate and calcium arsenate for the codling moth larva (Carpocapsa pen monella) was made recently by Marshall (119), Washington Experiment Station, Wenatchee. Although the crop and ventriculus of this larva are definitely alkaline in reaction (pH about 8.7), the alimentary fluid is well buffered even in the presence of an active acidity of pH 3.3. The results are interesting in the light of Swingle's (161) conclusion that acid lead arsenate is most toxic to insects having midintestines with alkaline reactions, while
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calcium arsenate is most toxic to those with mid-intestines of acid reaction, for experiments have shown that lead arsenate is more toxic than calcium arsenate t o the codling moth larva. A contribution by Staudenmayer and Stellwaag (158) furnishes new information on the hydrogenion concentrations and buffer values of the intestines of a number of insect species in relation to their food. Some insects apparently have the ability to regulate actively the buffer value of the intestine, and this ability may prove of great assistance to such insects in reducing the toxic effects of certain compounds. Hoskins (86), University of California, Berkeley, discusses at some length the relationship between pH of the intestine and the toxicity of ingested poisons. The experiments of Swingle (162), Bureau of Entomology and Plant Quarantine, with respect t o the effect of previous diet on the toxicity of lead arsenate to the southern army worm (Prodenia eridania), the results of which show that the resistance of the insect to the poison can be controlled to a marked degree by the previous diet, raise a number of interesting questions. Ginsburg (55), New Jersey Experiment Station, New Brunswick, has continued
78 the investigation of substances in spray water that have a solvent action on lead arsenate. In the study referred to, some 50 salts present either in soils or in spray waters have been examined for solvent action on acid lead arsenate. The nitrates, sulfates, and acetates were relatively nonreactive; the chlorides, silicates, and bicarbonates were moderately reactive; while the carbonates and sulfides usually formed a large percentage of soluble arsenic. The three calcium phosphates and the monobasic sodium and potassium phosphates formed little, while the dibasic and tribasic phosphates of sodium and potassium formed m u c h soluble arsenic. Solubility in water and a high pH value of the solution are determining factors in the solvent action of salts on acid lead arsenate. Goodhue (60) has applied a method of sedimentation analysis t o a study of particle size of commercial samples of acid lead arsenate. Commercial lead arsenate is a very fine powder; from 10.5 t o 60.3 per cent of the particles of 12 samples were as fine or finer than the finest samples of calcium arsenate and much finer than any of the samples of Paris green examined in this study. Loose bulking value (cubic inches per pound) was not closely correlated w i t h particle size. Gooden and Smith (58) have developed an air-permeation apparatus for measuring the average diameter of the particles in powders. Measurements are made rapidly and conveniently with this apparatus. McGovran et al. (110), Bureau of Entomology and Plant Quarantine, have determined that the finer particles of Paris green (average diameter 1.1 microns) produce higher mortality of and permit less feeding by Mexican bean beetle larvae (Epilachna varivestis) than samples with particles of 12 microns average diameter, notwithstanding a higher content of watersoluble arsenic in the larger particles. Efforts have recently been made to produce a calcium arsenate which will not injure the foliage of fruit trees. Pearce and Avens (182), N e w York Experiment Station, Geneva, have prepared and tested on the codling m o t h such an arsenate. It was made by adding a solution of arsenic acid to a boiling suspension of calcium hydroxide and holding the mixture at the boiling temperature for 1.5 hours. T h e product contained, on the dry basis, 45.7 to 45.9 per cent of arsenic as As2Os, and 0.45 to 0.55 per cent of water-soluble arsenic. T h e insecticidal results with this product were equal t o those from lead arsenate, and when sufficient calcium hydroxide was added t o the spray mixture, injury to apple foliage was eliminated. Gaines (49) and Smith, Scales, and Gaines (155) have lately t e s t e d calcium arsenates of different content of water-soluble arsenic against the boll weevil (Anthonotnus grandis) and the cotton leaf worm {Alabama argillacea). In the laboratory, t h e calcium arsenates of high (10.5 per cent) and intermediate (4.5 per cent) con-
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tent of water-soluble arsenic differed little from each other in toxicity to these insects; but both samples were significantly more toxic than the sample with low content (0.4 per cent) of water-soluble arsenic. In field experiments, however, these differences were not maintained. Dicalcium arsenate was more toxic to the boll weevil than either basic calcium arsenate or commercial calcium arsenate. Hansberry and Chiu (78) compared the toxic efficiency of calcium arsenate with calcium arsenite and lead arsenate, using the confused flour beetle as the test insect. Initial rate of mortality for lead arsenate was slower than for the other compounds, while calcium arsenite was least repellent. Basic copper arsenate has recently been investigated b y a number of workers. EUisor and Blair (43), Louisiana Experiment Station, Baton Rouge, compared t h e effectiveness of this compound with several other arsenical and fluorine compounds; the velvet bean caterpillar (Anticarsia gemmatilis) was the test insect. Basic copper carbonate proved highly toxic and possessed excellent adherent qualities. Further insecticidal information on basic copper arsenate is furnished by Felt and Bromley (45), Bartlett Tree Research Laboratories, Stamford, Conn. The influence of temperature on the toxicity of lead arsenate and cryolite t o t h e southern army worm (Prodenia eridania) and t h e velvet bean caterpillar (Anticarsia gemmatilis) has received the attention of EUisor and Floyd (44)- All t h e compounds except cryolite were more toxic, on the basis of median lethal dosage, at the lower temperature (15.6° C.) than at the higher temperature (26.7° C.), although the m e a n survival times were shorter at the higher temperature. Previous trials with aluminum arsenate a s a stomach poison have been disappointing; but in a recent paper, Paillot (181) reports success with a "nascent" alumin u m arsenate prepared b y mixing sodium arsenate with aluminum sulfate. The mixture proved as effective as lead arsenate against vine moth larvae and at appropriate concentration it did not injure t h e grape vines. Of interest to insecticidal chemistry is a paper by Garrett et al. (51) on the solubility of arsenious oxide in dilute solutions of hydrochloric acid and sodium hydroxide. Cassil (21) suggests improvements in the rapid volumetric micromethod for arsenic in insecticides. H a m mond and Maclntire (72) describe the thorium nitrate titration of microquantities of fluorine in aqueous and alcoholic solutions. Clifford (28) discusses some of the difficulties in adapting the WillardWinter method for fluorine to microquantities, and considers the possibility of determining fluorine with aluminum and aurintricarboxylic acid (aluminon). Donovan (87) gives some additional in-
Vol. 19, No. 2 formation on the determination of fluorine. Several insecticidal studies of fluorine compounds are noteworthy. Wilcox and Stone (178), Bureau of Entomology and Plant Quarantine, find a cryolite-talc d u s t and a cornmeal-cryolite bait promising in control of the corn earworm on tomatoes; and Gilbertson and Horsfall (S3), South Dakota Experiment Station, Brookings, report a barium fluosilicate-wheat flour dust the most efficient of several insecticides for controlling blister beetles. Most efforts to control insects by introducing toxicants into the food plant h a v e either failed entirely or have met w i t h only partial success. During the year, results with selenium of perhaps farreaching significance have been reported. Neiswander and Morris (126), Ohio Experiment Station, Wooster, nearly eliminated infestations of the red spider (Tetranychus telarius) from tomatoes, stocks, and roses grown in nutrient solutions containing 90 t o 100 p. p. m . of selenium as sodium selenate. On carnations grown in selenized soil, red spiders were practically eliminated by selenium a t 4 p. p. m., and the chrysanthemum aphid (Macrosiphoniella sanbomi) did not survive on chrysanthemums when the selenium concentration of the foliage was 45 p. p. m. Leukel (106), Bureau of Plant Industry, was able to eliminate infestations of aphids and red spiders from sorghum b y growing the plants on selenized soil. Although selenium i s so toxic t o higher animals that the use of considerable concentrations is precluded, nevertheless these studies suggest possible insecticidal uses for sublethal concentrations. Yellow phosphorus has long held a n i m portant place in the control of cockroaches, y e t little information is available o n t h e nature of its insecticidal action. Cheng and Campbell (24), Ohio State University, Columbus, contribute the first careful study on this subject. The median lethal dose of phosphorus for the large American cockroach b y mouth was determined as 0.02 mg. per gram of bodyweight, and by injection as 0.04 to 0.08 mg. per gram. T h e German cockroach was somewhat more resistant. Yellow phosphorus is also lethal by contact and in small spaces it m a y act as a fumigant. An active interest continues in t h e research on antimony compounds as insecticides and their use in practical control is expanding. Starr (157), Bureau of E n tomology and Plant Quarantine, has devised a method for detecting the distribution of potassium antimonyl tartrate (tartar emetic) on the foliage of trees sprayed with this compound. The basis of the method is a n iodine-starch test paper sensitive t o 0.9 microgram of tartar emetic per square centimeter of leaf surface. Persing et al. (185) report further studies on antimony compounds i n control of the citrus thrips (Scirlothrips citrt). From the standpoints of insecticidal effectiveness, availability, and cost, potassium
January 25, 1941
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79
antimonyl tartrate and calcium antitution and toxicity to the screwworm. effect. N o t only was rotenone without monyl tartrate were superior t o the other However, some chemical groups contained noticeable harmful effect, but it was the antimony compounds tested. Antimony more toxic compounds than others, this most efficient compound in controlling t h e sprays for thrips control are most effecbeing especially true of the nitro comflies. Bruce (15) also tried to prevent tive when they contain a carbohydrate pounds. hornflies and other blood-sucking flies substance, and of these sucrose and brown A study of nicotine base and of nicotine from attacking cattle by building up a sugar were most effective. Tsrtar emetic in several relatively insoluble forms lethal concentration of arsenic in t h e in the form of dusts was blood of the animals not as efficient for thrips through injection of mcontrol, as tartar emetic amino-p-hydroxyphenyl n ^~~^ o sprays. Lewis (107) has arsine oxide. T h e tests ^-*""'-—sri^2 = 5^ =:: *'^^ -__^=r--*.- " t l ^ ^ * ^ 2 ^ developed equipment for were unsuccessful. ' * / * - J.-S--^"','- .-. the application of tartar Potts (187) brings l \ emetic as dusts and together the results of jul. V | sprays. Weigel a n d several years' experience I !i -"* .*"v l" Johnson (172), Bureau of with concentrated spray ; ' ' ' • / ] " -».-, ^•jr" 1 •J,~ 1 Entomology and Plant mixtures. These mix] : ; 7 ' M K ' ' j ' " 1 Quarantine, have detures are designed t o i,= veloped a tartar emetic take the place of ordiil . ' ' • ^ I spray containing glycerol r =. nary sprays and dusts in place of brown sugar for aerial and ground i \ t! for the control of the red application. spider. Allman (8) finds / i tartar emetic equal to, if V _ Contact Poisons not better than, sodium fluosilicate for the conImportant contributrol of the Queensland tions to the chemistry fruit fly (Strumata and insecticidal action tyroni). of contact poisons have Bushland (17), Bureau been made during t h e of Entomology and Plant year. In a study of the Quarantine, makes an permeability of the i n important contribution sect cuticle, Hurst (89), on the toxicity to young at the Biological Field screwworm larvae (CochStation, Imperial College liomyia americana) of a of Science and Techgroup of compounds renology, Slough, Englated t o phenothiazine. land, attacks some of the U . S . O . A . P H O T O BY K I L L I A N Most toxic were acridine fundamental questions H. L. J. Haller experiments with insecticides by isolating the principles from and phenazine, but pheconcerned w i t h t h e plants that kill insects and develops method for making them synthetically. nothiazine itself killed all passage of toxic comthe larvae at a concenpounds through t h e tration between 0.03 t o 0.05 per cent. (nicotine caseinate, nicotine peat, nicoinsect integument. H e finds the outer, Alterations of t h e molecule sometimes protine stannous chloride, nicotine reineckate, lipoid layer of the integument relatively duced marked changes in toxicity—for nicotine silicotungstate, nicotine alkylimpermeable t o polar compounds such a s example, when the sulfur of phenothiazine phenylbenzene sulfonate, and nicotine ethyl alcohol and acetic acid, while t h e was replaced b y oxygen, the resulting com2,4-dinitro-6-cyclohexylphenate) has been inner, chitinous layer, essentially a mixpound was reduced in toxicity to about one published by Hansberry et ah (74). Adture of chitin and proteins, is relatively fifth that of the parent molecule On the ministration of the preparations was permeable to both polar and apolar comother hand, the oxidation of phen.. sulfide either by mouth, by injection into the pounds. However, the permeability of to diphenyl sulfoxide yielded a cc pound intestine, or into the blood; the test inthe lipoid layer t o polar compounds is that was more toxic than the pai it subsects were lepidopterous caterpillars of greatly increased by the presence of apolar stance. I n a second paper (18) results are several species, larval and adult Colorado substances—for example, when a mixture given for a group of 551 organic compotato beetles (Leptinotarsa decemlineata), of ethyl alcohol and paraffins is applied t o pounds which were tested against young and adults of t w o species of cherry fruit the cuticle, the polar compound will penescrewworm larvae. Among the hydrocarflies. Large species differences in sustrate the outer lipoid layer and then difbons in this group, phenanthrene and ceptibility t o nicotine were observed; fuse through the chitinous layer beneath. diphenyl were outstanding—i. e., killed but the differences between ingested and The diffusion of any mixture is governed by all the larvae a t 0.10 per cent or less— injected nicotine were not highly signifimutual solubilities and the pathological but there w a s only one diphenyl comcant. changes occurring in the tissues. Apolar pound, p-chlorodiphenyl, which was more The investigation by Bruce (18) on the compounds increase the permeability of the toxic than the parent compound. Most medication of cattle with phenothiazine cuticle in both directions, but the increase of the nitro compounds were highly toxic, to prevent breeding of the hornfly (Haefrom lipoid layer to chitin layer is the more and all the nitro-halogen combinations matobia irritans) has been extended (14) pronounced. T h e relation between powere outstandingly so. High toxicity was to include besides phenothiazine 28 other larity and induced penetration applies t o noted also in the quinoline derivatives. compounds. Of these, azobenzene, 2,4such feebly dissociated compounds as T h e halogen derivatives, azobenzene dedinitrophenylhydrazine, p h e n o t h i a z i n e , alcohols, fatty acids, phenols, iV-heterorivatives, and compounds with aromatic and rotenone prevented the breeding of cyclic bases, ammonia, and hydrogen hydroxyl groups and those with methoxyl hornflies in the droppings of cattle which cyanide. The strongly dissociated neuor ethoxyl groups contained a smaller had been fed these compounds b y mouth. tral salts and mineral acids scarcely show proportion of compounds with marked However, all t h e successful compounds this phenomenon. T h e results of the ininsecticidal action. N o simple relationexcept rotenone either were distasteful to vestigation lead t o the very important ship was found between chemical constithe cattle or produced some harmful conclusion that each constituent of a poi* • "
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80 son mixture may contribute to the toxic action even though, alone, it produces no toxic effect. O'Kane et al. (ISO), New Hampshire Experiment Station, Durham, have continued their studies on the penetration of compounds into the insect integument. Working with the freshly removed pronotum of the cockroach, six alcohols, two petroleum products, and pine oil were examined with respect to permeability. Methyl alcohol penetrated most rapicUy, while several of the higher alcohols, notably octyl and isopropyl, passed through the integument much more slowly. The rate of passage was not uniform for all the compounds, isopropyl and butyl alcohols lagging behind the others at the start. The authors suggest that the wax-solvent properties and the size of the molecule, among other things, affect the speed of penetration. Hockenyos (80) believes the integument of Periplaneia americana has the properties of a semipermeable membrane coated with a film of waterresisting fat or oil, and that the rate of adsorption of sodium fluoride by the integument is influenced by osmotic forces, by temperature, and by chemical materials that adsorb or react with the film. Persing et al. (185) describe the use of a sulfur dust with particles having a maximum diameter of 40 micr6ns for the control of citrus thrips (Scirtothrips citrt) on lemons and oranges; and Gaines et al. (50) find that melon aphids (Aphis gossypii) increase in numbers on cotton after application of calcium arsenate, while fight infestations of certain plant bugs are controlled by the same treatment. Two contributions furnish new information on the insecticidal action of /3-butoxy-/3-thiocyanodiethyl ether. Potter and Musgrave (136) and Callaway and Musgrave (19) have tested the compound on a considerable number of species, to most of which it was toxic both as a fumigant and a contact poison. It proved more toxic to eggs of the bedbug than a-naphthylisothiocyanate, iauryl thiocyanate, or pyrethrins. Hartzell and McKenna (77) obtained encouraging results with fr/S'-dichloroethyl ether in a spray containing a low concentration of pyrethrins for the control of the gladiolus thrips (Taeniothrips simplex). In a paper on contact insecticides for the bedbug (Cimex lectularius), Hockenyos (82) discusses diamylphenol, a relatively new, odorless insecticide. In laboratory experiments, by the falling mist method, this compound gave rather poor results; however, Jennings (98) found it one of the most promising contact insecticides tested by him for controlling carpet beetles. Most of the interest in petroleum oil insecticides during the past year has centered around oil sprays fortified with other toxicants. A few papers of interest, however, deal with sprays containing unfortified oils. Hensill (79), California
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Spray-Chemical Co., Whittier, offers a method for determining spray-oil deposits on plant surfaces in the field and laboratory- The method is based on the unsulfonatable residue of the oil recovered from freshly sprayed leaves by means of acetone. Ginsburg (56), New Jersey Experiment Station, New Brunswick, reports the results from extensive teste of semirefined and highly refined oils as summer sprays on apple trees A semirefined distillate of 70 seconds' viscosity (Saybolt 100° F.), about 83 per cent unsulfonatable residue and viscosity index of 90 to 100 proved to be as safe on the foliage as highly refined oils that cost about twice as much. Buckell (16) uses oil sprays as adjuncts to poisoned baits for destroying such species of grasshoppers as Camnula pellucida on the egg beds and congregations of the destructive Melanoplus m. mexicanus when the weather is not favorable for the use of poisoned baits. The spray mixture consists of Diesel oil emulsified with casein spreader; it is applied with orchard sprayers mounted on trucks. Lamerson and Parker (101) find a mixture of nicotine sulfate or nicotine and an emulsion of highly refined petroleum oil the most effective treatment for the strawberry leaf roller (Ancylis fragariae) from time of hatching until the larvae begin to roll the leaves. Husen (90), Commerce Petroleum Co., has studied the staining of wallpaper by insecticides made with petroleum-base solvents which are commonly applied in dwellings. Other types of solvents were included in the investigation. All the petroleum-base solvents examined (mineral spirits, kerosene types) produced the same staining effect. Toxicants added to the solvents slightly intensified the degree of staining. Starch-type papers showed the most pronounced stains; rotogravure ink-type papers with varnish-type binders were least affected. The degree of staining was increased with increased moisture content of the papers. An investigation of the performance of hand insecticide sprayers, of the type commonly used to apply household sprays, has been made by Hursh (88), Ohio State University, Columbus. Great differences were observed in the mechanical performance of the various types and sizes of sprayers examined; and while no general conclusions are drawn from the investigation, Hursh states that mechanical performance of a sprayer depends largely on the construction of the orifice and the dimensions of the cylinder.
Control of Termites and Other WoodInfesting Insects Improvements are noted in the use of soil poisons for the control of termites. Hockenyos (81, 88) discusses the physical characteristics of soil in relation to the application of soil poisons. Capillarity, adsorption, size of soil particles, and
Vol. 19, No. 2 moisture content are some of the factors which influence their effectiveness. Among thp older soil poisons &re o-dichlorobenzene, monochloronaphthalene, anthracene oil creosote, jS-naphthol, sodium arsenate, and sodium arsenite; of \.he promising newer materials trichlorobuizene, pentachlorobenzene, and tetrachlorophenol are noteworthy, while diphenylamine, acid lead arsenate, and borax are still undergoing experimental trial. The Termite Committee of the National Pest Control Association (5) has recently outlined specifications for the use of soil poisons in controlling termites. Progress in the control of Lyctus powder post beetles in lumber is reported by Christian (25), Chicago Mill and Lumber Co., Tallulah, La. For green lumber, as it comes from the saw, an aqueous solution of borax gave the best results, while for lumber en route from the millyard to the consumer, a solution of pentachlorophenol in fight fuel (petroleum) oil was the most effective treatment. Methyl bromide fumigation showed promise for controlling Lyctus beetles in loosely piled boards 1 inch or less in thickness. Further details concerning these treatments are given by Christian (26). The same investigator (26) prevented damage to hardwoods by ambrosia beetles (certain species of the family Scolytidae) by application of dichlorodiphenyl oxide, (p-ferf-butylphenoxy) ethanol, p-chlorophenoxyethoxyethyl chloride, and o-nitrodiphenyl, the first three compounds dissolved in kerosene, the latter compound in benzene. Nettles (127) has devised a method of treating green fence posts with an aqueous solution of copper sulfate which renders the wood immune from the attack of insects and decay organisms. Nondurable wroods such as sap pine can be preserved by this method.
Insecticides of Plant Origin Worsley (177) has studied the histology and physiology of the rotenone-like substances in various plants of the family Papilionaceae. For these substances, he proposes the name "rotenoids", and includes under that term all the naturally occurring substances in these plants that respond to the Durham test. Fourteen of the 22 species of plants examined in this family contained rotenoids. Rotenoids disappeared in the germinating seeds of all species examined and in the fignifying pith of two species. They appear to be of some use to the germinating seed and seedling, but are probably waste products in all other tissues. Rotenoids are apparently confined to the two plant subtribes, Tephrosae and Lonchocarpae, of the tribes Galageae and Dalbergeae. Roark (141) points out that the term rotenoid has already been used, with several different meanings, in the patent literature, and further that the Durham color test, used by Worsley, is unreliable.
January 25, 1941 But the word is useful and it is destined to enter the vocabulary of entomologists; therefore Roark offers this definition: "A rotenoid is a substance other than rotenone, but structurally related to it, naturally occurring in leguminous fishpoison plants (e. g., Derris, Lonchocarpus, Mundulea, and Tephrosia)." Examples of rotenoids are: Z-deguelin, l-a-toxicarol, sumatrol, and elliptone. Sorrel (156) describes the growing and marketing of timbo in Brazil. Para timbo consists chiefly of the species Lonchocarpus urucu, L. floribu7idust and L. nicou. The rotenone content of the cut root and of the various i milling products is given. Sievers (149) contributes a paper on the production and marketing of derris. Georgi and Teik (52) have studied the effect of age on the rotenone and total ether extractives of the plant, Derris malaccensis, var. sarawakensis. Both rotenone and ether extractives decreased after the plants were 23 months old. The proportion of rotenone to extractives was 20 per cent, or 5 per cent higher than the proportion usually reported for roots of this species. Sievers et al. (150) investigated the effect of the seasonal growth period on the insecticidal value of the devil's shoestring (Tephrosia virginiana) produced under cultivation in northeastern Texas. Clonal progenies of the same parent plant did not differ significantly in rotenone, total chloroform-extractives, or toxicity to houseflies; but significant differences were found with respect to these factors* in the progenies of different parents. Roots harvested in the fullbloom period were higher in rotenone, extractives, and toxicity than those harvested at other times. The leguminous plant, Mundulea serica, var. "Supli", of India is reported by Tattersfield and Potter (164) to possess substances in the leaves, bark, and roots with marked insecticidal properties; yet these substances are of a lower order of toxicity than those present in the roots of Derris eUiptica. New compounds are currently being discovered in Derris roots. From D. malaccensis (Kinta type roots), Harper (76), Rothamsted Experimental Station, Harpenden, Herts, England, announces the finding of a new optically active phenol isolated from the ether extract of the ground roots. This compound, called malaccol, has been assigned the formula C20H18O7, and a study of its reactions suggests the structure 15-hydroxyelliptone. The insecticidal action of malaccol has not yet been reported. The possibility of a domestic source of rotenone through cultivation of native species of rotenone-bearing plants, has prompted Goodhue and Haller (68) to study the noncrystalline constituents in the roots of Tephrosia virginiana. A new substance, melting at 76° C , found in the alkali-soluble fraction, and deguelin are reported for the first time from this plant, although deguelin has been found previously in other species of Tephrosia. Two
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other crystalline compounds were isolated—an orange-yellow compound melting at 125° C. which is given the tentative formula C22H24O4, and a compound melting at 131° C. which is identical with one isolated by Clark (27) and assigned by him the formula C22H24O4. In another paper, Goodhue and Haller (64) present
Grass-feeding grasshoppers controller! by poisoned bait, North Central States
an analysis of the water extract of derris, cube*, and timbo. A single extraction with water removed from 24 to 41 per cent of the insecticidal material, while successive extractions removed more. When preserved against fermentation, this extractive material was very stable. Progress is reported in methods for analysis of rotenone and related compon ids, A contribution from the Rothamsted Experimental Station, by Martin (121) considers the problem of evaluating the relative insecticidal potency of derris roots of several species and of the same species from several localities. Various methods based on chemical analysis, optical rotational values, and certain biological tests were examined and found inadequate. It was discovered, however, that, if for a group of derris samples a summation was made of the percentage of rotenone, one fifth of the percentage of the deguelin concentrate fraction, and one fifteenth of the percentage of the toxicarol fraction, a value was obtained, called the rotenone equivalent, which expressed very closely the relative toxicity of the samples to Aphis rumicis. An alkaline fractionation method is described which enables one to determine the rotenone content as well as the rotenone equivalent of a derris root. Graham (67), Food and Drug Administration, United States Department of Agriculture, discusses the use of decolorizing carbon and other details in the analysis of derris and cube* powders for rotenone. Meijer and Koolhaas (123), Laboratory for Chemical
81 Research, Buitenzorg, Java, compare an ether-extraction method for rotenone (100) with the United States ofiicial method (94) I the pure rotenone content by the former method equaled the crude rotenone by the latter method. They also describe a method for determining rotenone in the resin which has escaped estimation, based upon passing the benzene solution of the resin through an activated fuller's earth. Experiments on heating derris powder before analysis for rotenone showed that temperatures above 50° C. definitely lowered the rotenone and ether-extractive content. The fraction of derris and cube", which is insoluble in alkali and which has been assumed to consist largely of optically active deguelin, has, according to Goodhue and Haller (61), about the same insecticidal action as rotenone, although racemic deguelin is much less toxic. Since the toxicity of the noncrystalline fraction of derris may be due to optically active deguelin, these authors propose a method for the determination of this compound. The method consists essentially of treating the alkaliinsoluble resins with a dilute solution of potassium hydroxide in methyl alcohol which changes the optical isomer to racemic deguelin. The latter is purified by crystallizing from carbon tetrachloride and then weighing the deguelin as the 1:1 carbon tetrachloride solvate. Purity of the solvate is determined by the redcolor test as modified by Goodhue (59). Samples of two species of derris, of cub£, and of timbo contained generally less than 1 per cent of deguelin. In view of the low concentration of deguelin and the high toxicity of the noncrystalline fraction of these samples, it is suggested that other yet unidentified substances contribute to the pronounced insecticidal action. Among the many derivatives of rotenone which have been prepared in the laboratory, only one, dihydrorotenone, approaches the parent compound in toxicity to insects. There are indications that dihydrorotenone may be more stable than rotenone to oxidation in light and as dihydrorotenone has now become commercially available, methods for its determination are timely. Goodhue and Haller (62) propose two methods. iFhe first depends on the greater solubility in benzene of dihydrorotenone than of rotenonic acid, dihydrorotenonic acid, and dihydrorotenol, the three most common by-products of the catalytic hydrogenation of rotenone. This method serves as a simple distinguishing test for dihydrorotenone. A more accurate method is afforded by a modification of the redcolor test (59); it depends on the fortunate circumstance that, of the four compounds produced when rotenone is hydrogenated to form dihydrorotenone, only the latter compound gives a red color comparable to that given by rotenone. Mixtures of rotenone-bearing materials with alkaline diluents have generally resulted in the loss of insecticidal potency.
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U. S . D. A. PHOTO BY KILLIAN
Entomologists determine the response of the cockroach's heart to nicotine by recording photographically the heart movements before and a f t e r contact with t h e nicotine. Allen and Brooks (#), University of Wisconsin, Madison, have recently investigated this subject with special reference t o the preparation of stable dust mixtures. Dusts prepared with such alkaline diluents as talc, copper carbonate, magnesium carbonate, and m calcium hydroxide, having a pH range of 8.24 to 12.50, and kept in damp storage for 7 days, showed a definite loss of toxicity to houseflies. D u s t s made with acidic diluents (pH range 4.23 t o 8.03) on the other hand, and stored under the same conditions, retained their toxicity. However, dry or unmoistened alkaline and acidic dusts remained unchanged in toxicity. A mixture containing 25 pounds of derris, 37.5 pounds of calcium hydroxide, 37.5 pounds of sulfur, and 5 pounds of nicotine sulfate (40 per cent) formed a stable dust for the control of chewing and sucking insects o n cabbage
(m. Plants in foliage are limited with respect t o the quantities of a petroleum oil spray they can tolerate without injury; and in efforts t o extend the use of oil sprays, many attempts have been made to increase their toxicity per unit of oil by the addition of other toxicants. Rotenone and the rotenoids are not sufficiently soluble i n petroleum oil or in water to be dissolved directly in oil emulsions; but recent investigations have produced several mutual solvents for rotenoids and petroleum oil, among them being dibutyl phthalate, (4-tertiarybutylphenoxy) ethanol, and Cardolite, the latter a-phenolic resin. Ebeling (41, 42) h a s obtained higher mortality of the difficultly con-
trolled California red scale (Aanidiella aurantii) with a derris resin-dibutyl phthalate—-petroleum oil spray than with the oil spray alone, and at a lower oil deposit per ianit area of foliage. T h e addition of waJjiut-shell flour to these sprays increased insecticidal effectiveness and probably reduced foliage injury. Boyce et dl. (11) jreport a similar experience with deriis-petr-oleum oil sprays containing a mutual soW e n t for the control of the black scale (Saissetia oleae) and citricola scale (Coccus ff^eudomagnoliarum); but the addition of walnut-shell flour and similar materials -feo these sprays seemed t o affect adversely "the control of black scale. T h e effectiveness of smoke from burning pyrethruro. as a n insecticide has been known for- a long time; but there is little information on t h e toxicity of the smoke from, burndng derris. Goodhue and Sullivan (65) "tested t h e smoke from a burning mixtirre of derris, cornstalks, and sodium nitrate o n houseflies in a PeetGrady chamber. Derris smoke proved to be more t h a n ten times as toxic to these insects a s the smoke similarly produced from burning pyrethrum. Derris smoke also killed the bean aphid (Aphis rumicis) but the Aonerican cockroach (Periplaneta anzericance^) was n o t affected by it. Apparently r-otenone is n o t entirely destroyed by combustion under these conditions, since it vsras present i n the smoke for at least an hour after burning. Sullivan, Goodhue, and Fales (159) have tested aerosols pwoduced. by spraying safrol solutions of rotenone and pyrethrum oleoresin ori a surface heated t o 375° C ; they
Vol. 19, No. 2 proved toxic to houseflies, cockroaches, and mosquitoes. The materials were tested alone and as mixtures. All tests on the housefly gave at least 74 per cent mortality in 72 hours; and a mixture of rotenone and pyrethrum produced 95 per cent mortality. The aerosols were n o t toxic to the American cockroach; on t h e other hand, culicine mosquitoes succumbed in 10 minutes t o aerosols from alcoholic extracts of pyrethrum. The effect of temperature on the t o x icity of rotenone-bearing dusts to the larva of the Colorado potato beetle has been studied by Feytaud and deLapparent (46), At 10° C. and higher temperatures, the speed of toxic action increased with the rise in temperature; but below 10°, the toxic action decreased. A t e m perature of 28° C. favored contact action. Talc-rotenone dusts were more effective than pure cube* powder of the same rotenone content, owing probably to a desiccating effect of the talc. Regarding the toxicity of rotenone-bearing materials t o vertebrate animals, Haag and Taliaferro (70) have recently published the results of a toxicological study of cub6, with the rat as the experimental animal. Using a sample of cube" which contained 4.7 per cent of rotenone and 19.7 per cent of total carbon tetrachloride extractives, the acute median lethal dose by mouth was 170 mg. of cube per kg., while as much as 300 p. p . m. fed daily with the food did not affect the growth of the animals. During the last year, progress has been made in elucidating the structure of t h e pyrethrins and in improving methods for their assay. Acree and La Forge (1), Bureau of Entomology and Plant Quarantine, are studying the nature of the u n saturated side chain present in pyrethrolone; the reactions of pyrethrone, t h e desoxy derivative of pyrethrolone, with bromine in certain solvents appears t o be strictly analogous t o those exhibited by the allenes. Holaday and Graham (85) have investigated the Wilcoxon method for pyrethrin I (174) as modified by Holaday (84). The modified method depends upon the reduction of Deniges* reagent by pyrethrum I, and precipitation of the reduced mercury as mercurous chloride, which is then determined by titration with potassium iodate solution. Erroneous results obtained by the original Wilcoxon procedure are believed to arise from the presence of unsaturated organic compounds which introduce an error in the iodate titration. Washing t h e mercurous chloride precipitate with t h e proper solvents before titration obviates this error. Sherman and Herzog (146), Cooper Union Institute of Technology, N e w York, have also studied the WilcoxonHoladay method and suggest improvements in certain details. Graham (67) discusses this method at some length, and in addition comments on the Seil method (144) for pyrethrin I I . T h e deterioration of pyrethrum powder
January 25, 1941 in pyrethrin content is of considerable importance t o those who handle and use this material. Weed (170), John Powell and Co., N e w York, presents some timely statistics on this subject. Pyrethrum powder of 0.5 to 0.6 per cent initial pyrethrin content loses 9 to 15 per cent of the pyrethrins in 6 months; powder of 0.8 to 1.0 per cent content loses 10 t o 16 per cent in 6 months; and powder of 1.1 per cent and higher initial content suffers a reduction of 14 to 20 per cent in the same period of time. T h e loss increases with advancing age of the powder but the rate of loss becomes progressively less. Samples 10 years old or older may still contain as much as 0.42 per cent pyrethrins. Troisier (167), Davis-Young Soap Co., has studied the stabilization of pyrethrins in pyrethrum insecticides by means of antioxidants. Benzaldehyde, low titer oleic acid, and a nonvolatile olefin were effective antioxidants. Vanillin also showed antioxidant properties, but it had an injurious effect on fly spray preparations. From the standpoint of pyrethrum as an insecticide, the recent work of Smith and Sullivan (154) on the very resistant blister beetles is of interest. Derris powder enhanced the toxicity of pyrethrum extract considerably, a spray containing pyrethrins 1:5000, derris as rotenone 1:4000, and a commercial spreader being most potent. Gnadinger, Moore, and Coulter (67), McLaughlin Gormley King Co., Minneapolis, Minn., have attempted to control the codling moth on apples with some of the newer types of pyrethrum insecticides. The overwintering larvae were killed on the trunks and leaders of the trees with a kerosene-pyrethrum spray; the larvae hidden in the crotches, scars, and cracks were reached by applying the same preparation by means of a pressure oil can; the moths and the larvae which had left the fruit were killed by means of a talc-pyrethrin dust. Between the dust treatments, petroleum oil sprays were used for their ovicidal and other toxic effects. T h e authors describe a pyrethrum dust, recently developed, and containing 0.2 per cent pyrethrins, which is more effective than pyrethrum powder containing 0.9 per cent total pyrethrins. Barber (10), Bureau of Entomology and Plant Quarantine, gives detailed directions for controlling the corn earworm (Hdiothis armigera) on sweet corn by means of petroleum oil containing pyrethrins. Several new methods for the determination of nicotine are reported by Markwood: a rapid turbidometric method for the determination of small quantities of nicotine as the phosphotungstate (114), a method for the determination of nicotine in fresh tobacco leaf (US), and a study (118) of the quantitative characteristics of the nicotine color reaction with cyanogen bromide and /5-naphthylamine. The latter reaction m a y be used in the quantitative estimation of nicotine by colorimetric methods. A long-needed study of the distribution
NEWS
EDITION
of nicotine between petroleum oil and water has been published by Norton {128), New York Experiment Station, Geneva. Nicotine-petroleum oil emulsions find important insecticidal uses, yet the factors which govern the distribution of nicotine between the oil and water phases of the emulsion have been incompletely understood. A t low alkaloid concentrations, nicotine is nearly equally distributed between the oil and water; but with increasing concentration relatively more of the alkaloid passes into the water phase until a maximum is reached. At high alkaloid concentration, the distribution with respect to water decreases. Acids bring the nicotine into the water phase and hold it there in amounts equal to the acid equivalence, any excess amount being equally divided between the water and oil. Alkalies do not affect the distribution until they reach 0.1 N; but at higher concentration they force the nicotine into the oil phase. Only the free nicotine is shared between the oil and the water; and in the original spray mixture, the nicotine concentration in the oil and water will be approximately equal, regardless of the alkaloid concentration and of the presence of fungicides and emulsifiers. As the spray dries on the foiiage, some of the nicotine in the water is transferred to the oil. Dawsey and Mark wood (84, 85), Bureau of Ente mology and Plant Quarantine, have found that a mixture of bentonite and soybean oil is the best adhesive for nicotine sprays and that bentonite is superior to all adhesives tested for nicotine-
83 bentonite sprays. Richardson and EUisor (139), Iowa Experiment Station, Ames, found that neither lethal nor sublethal doses of molecular nicotine were more toxic than the same doses of ionic nicotine when they were injected into the body cavity of cockroaches (Periplancta americana). Hansberry and Norton (75), Cornell University, have prepared and tested the optically active nicotines and nornicotines as contact insecticides for Aphis rvmids, the insecticidal action of d-nicotine, £-nornicotine, and d-nornicotine being determined by them for the first time. All the nornicotines were more toxic to this insect than J-nicotine; on the other hand d-nicotine was considerably less toxic than Z-nicotine (188), and di-nornicotine had approximately the same toxicity a s the dand the Z-isomer, although
