E-451 UNITED STATES DEPARTMENT OF AGRICULTURE BUREAU OF ENTOMOLOGY AND PLANT QUARANTINE DIVISION OF INSECTICIDE INVESTIGATIONS STATfc igjS?*** THE ARSENATES OF MAGNESIUM AS INSECTICIDES (A REVIEW OF THE LITERATURE) By F. E. Dearborn Washington, D. C. October 1938 E-451 October . 1938 United States Department of Agriculture . Bureau of Entomology and Plant Quarantine TE3.AHSIaA.TSS OF MAGEESIEK A3 INSECTICIDES (A REVIEW OF THE LITERATURE) By F. E. Dearborn, Division of Insecticide Investigations Contents Page A. Occurrence of magnesium arsenates in nature 3 B. Chemistry of magnesium arsenates 3 1. Koncaagnosium or thoar senate, agE4(As04J2 2. Pi. agn.es ium or thoar senates (a) The compound MgEAs04.l/2FoO 4 ( b) The compound MgEABO^.SHgO 4 ( c ) The compound MgHAs04. 6 l/gHgO 4 (d) . The compound Iv;gHAs04 . 7H20 4 3. Magnesium pyroarsenate, luggAggO? 4 4. Trimagnesium or thoar senates (a) The compound I/:g3(As04) 2.7E20 4 (b) The compound Mg3(As04)n.8H20 5 (c) The compound Mg3(As04)2.10H20 5 (d) The compound Mg3(As04)2«22H20 5 5. Baric magnesium orthoar senates 5 6. Magnesium ammonium orthoarsenate 6 7. Double salts of magnesium arsenate 6 C. Patented methods of preparing magnesium arsenate insecticides 6 D. Analyses of magnesium arsenate insecticides 7 E. Compatibility of magnesium arsenate with fluosilicates and cryolite 10 P. Adhesives and carriers for insecticidal dusts 10 G. Application of magnesium arsenate as an insecticide 11 1. Mexican bean beetle (Epilachna varivc. stria (Muls . ) 11 2. Bean leaf beetle (Cerotoma trifurc-.it a (Por st . ) ) 19 3. Cooling moth (Carpocapsa pomonella (L. ) ) 19 4. Plum curculio (Cor. otr achclus nenuphar (Herbst)) 22 5. Japanese beetle (Popillia Japonic a (gewm. ) 23 6. Rusty tussock moth (£otolophuc ant i qua (L.) ) 23 7. Cranberry fireworm (Rhopobota vacciniana (Pack.)) 24 8. Potato flea-beetles (Epitrix cucumer i s .Earr 1 s and S. subcrinita Leconte) ; 24 - d - Page 9 . Oriental peach moth (Grapholitha molesta (Busck) ) 24 10. Bell weevil (Anthonomun grand is (Boh. ) ) 24 11. Cabbage insects 24 12. Strawberry root weevils • (Brachyrhimis ovatus (L.) and B . rugifrons ( Gy 11 . ) ) . . 25 13. Beet webworm (Loxostige sticticalis (L. ) ) 25 14. Turnip webworm 26 15. Spotted blister beetle (Epicauta maculata (Say)) 26 16. Black vine weevil (Brachyrhinus sulcatus (F. ) ) 26 17 . European corn boref: (Pyrausta nubilalis (Hbn.)) ....... I. 26 16. Blueberry maggot (Rhagoletis pomonclla (Walsh)) 26 19. Squash beetle (Epilachna borealis (P.)) 26 20. Plum web-sawfly (Neurotoma inconspicua (Norton) ) 27 21. Grape berry moth (Polychrosis viteana (Clem.)) 27 22. Green clover worm (Plathypena scabra (P.)) 27 23. The pyralid Maruca testulalis (Geyer) 27 24. Colorado potato beetle (Leptinotarsa decemlineata (Say)) 27 25. Red-legged grasshopper (Melanoplus femur -rubrum (Beg.)). 28 26. Lima bean pod borer caterpillars (Maruca testulalis (Geyer), Pundella cistipennis (Dyar), and Etiella zinckenella (Treit.)) 26 27. Gypsy moth (Porthetria di spar (L. ) ) 28 28. Miscellaneous 28 Literature cited 29 - 6 — A. Occurrence of Magnesium Arsenates in Nature Magnesium compounds arc widely distributed in nature, the arsenates occurring as the following minerals: Adelitc, Ca(MgOE)AsC>4 Berzeliitc, (CajMgjMnjNa^gCAsO^g Cabrerite, (Ni,Mg,Co)g(As04)2»8H20 Home site, Mg3(AsC4)2.8H20 Karyinite , (Mn , Ca ,?b , Mg) 3 (AsC^) 2 Picropharmacolite, (CaLigJ^AsC^g.-SEgO- r.oselit e , ( Ca,Mg ,00)3 (A SO4) 2 • 2H2O R6* ssler i te , MgEAs04« 1 / 2H2O Tilasite, Ca(I.g?)AsC4 B, Chemistry of Magnesium Arsenates The author does not vouch for the accuracy and results obtained in the preparation and properties of the various compounds given below. The result-, given are abstracts taken from the literature. Ordinary or orthoarsenic acid (H^AsO^) is a trior sic acid, and theoretically is capaole of forming three magnesium arsenates (1, 113, 116) the monomagnesium orthoarsenate [MgB^AsC^o]* the dimagnesium or t hoar senate (MgHAsC^) , and the trimagnesium orthoarsenate [hg.3(As04)2]. All these magnesium arsenates are known, two of them with. various amounts of water of crystallization, the number of moles of water depending upon the conditions under which the compound is formed. In general the compounds formed at low tempera- tures and from more dilute solutions contain the larger amount of water of crystallization, while those formed at high temperatures or from more concentrated solutions contain the smaller amount of water of hydration. 1. Monomagnesium orthoarsenate Monomagnesium orthoarsenate (62, 64) has the formula k'gH^AsC^p. Schiefer (133, 150) prepared the compound by heating a solution of magnesium oxide in arsenic acid, and obtained very hydroscopic crystals, soluble in water ♦ 2. Dimagnesium orthoarsenates The general formula for the dimagnesium orthoarsenates may be written as MgBA.sO4.XE2O, in which (X) represents the moles of water of crystallization. Salts have been prepared containing 1/2, 5, 6 1/2, and 7 moles of water of hydration. The general method of preparing the dimagnesium salt is to allow disodium arsenate (hao?IAs04) to react with magnesium sulphate (62, 63) in water solution, or by treating a solution of disodium arsenate (l\aphAs04) with acetic acid, and adding the calcu- lated amount of magnesium sulphate. The precipitate that first forms is amorphous, but soon crystallizes in leaflets. _ 4 - (a) The compo-und MgHAsO^.l/SHgO This compound occurs in nature as the mineral Rosslerite. De Schulten (.33, 39) prepared it "by heating magnesium carbonate in an excess of arsenic acid in scaled tubes, at 225 C. It crystallizes in colorless monoclinic leaflets, and has a density of 5.155 g/cc. at 15 C. (b) The compound MgHAs0A.5Eo0 ■ -<£■.'■ ■ Schiefer (62, 1.33, 160) obtained this compound by dissolving magr.essi"ar' pyroex seriate in acetic acid and allowing the salt to crystallire from the solution. (c) The compound MgEAs04.S l/SHgO In various handbooks (l, 75, 120) is described a compound contain- ing 6 l/2 moles of water of crystallization. It is a white crystalline co-;T'ound, insoluble in cold water; 0.15 part dissolves in 100 parts of water at 100° C. It is soluble in nitric acid, but insoluble in ammonium chloride. (d) The compound MgHAs04.7E20 This compound was prepared (3S, 62, 96) by dissolving the ignited residue of ammonium magnesium arsenate (magnesium pyroarsenate) in acetic acid, and allowing the salt to crystallize. It crystallizes in monoclinic leaflets (71, 72, 129) and is stable in air. Dried over sulphuric acid, 4,5 to' 505 moles of water of crystallization are removed. Dried at 100° C.j r,he compound loses 5 to 6 moles of water; and at 200° C. 6 moles of .iter of hydration are removed. On igniting, the compound is converted into magnesium pyroarsenate (MgoAsoOy). w 3. Magnesium pyroarsenate, MggAsoO? This compound is produced (62;, 64) by igniting the dimagnesium orthoar senate or the ammonium magnesium orthoarsenate compounds. 4. Trimagnesium orthoarsenates The general formula for the trimagnesium orthoarsenates may be written, Mgg^sO^g.XHgO, in which (X) represents the moles of water of crystallization. Compounds have been made which contain 7, 8, 10,. and 22 moles of water. The usual method of preparing the trimagnesium orthoarsenates (10, 62, 64) is to allow arsenic acid to react with mag- nesium hydroxide in the- proper proportions, as illustrated by the follow- ing equation; 3Mg(0H)2 + H3As04 - Mg3(As04)2 + 6H3O (a) The compound Mg3(As04)?.7E 0 This compound was prepared by Chevron and Droixhe (26, 62), using monosodi-um arsenate (lTaE2As04) , magnesium sulphate, and sodium bicarbonate, - 5 - (b) The compound MggCAsO^JlLg.BgO This compound occurs in nature as the mineral Hornesite (114). It crystallizes in moro'clinic prisms of light rose color. The density of the native compound is 2,474 g/cc \t 15° C. , while that of the prepared compound is 2,609 g/cc at 15° C. It is prepared (40, 62, 64) "by mixing at room temperature a solution of 20 grains magnesium sulphate (MgSO^.TEgO) dissolved in 1 liter of water with a solution of 16.9 grams disodium arsenate (HagKAsO^^^O) and 4,5 grams sodium bicarbonate dissolved in 800 cc of water. The precipitate that first forms is amorphous, "but after standing 24 hours or more at 20-25° C. the crystalline salt is formed, (c) The compound Ivig^AsO^g.lOHgO This compound (40, 62, 94) is prepared "by digesting ammonium magnesium arsenate (HILjMgAsO^ or potassium magnesium arsenate (KM^AsO^.) for a long time in water. It is also produced by the action of water on the compound Mgg^sO^ j*22H20. ( d) The compou id ...": ;3 (A sOu^g .22E20 This compound (40, 32, 64, 94) is prepared similarly to the com- pound containing £ moles of water Df hydration, "4th the exception that a lower temperature (10° 9.) and more dilute solutions are emplryed. After - standing 2-1- hours, crystals of the salt are collected. It crystallizes in monoclinic plates (71), of density of 1.788 g/cc at 15° 9, The salt slow- ly decomposes in the ai> . Under water it is converted into the salt con- taining 10 moles of water of hydration, Dessicated over sulphuric acid the salt remains 6 moles of water. Tried at 190c 9, it retains 5 moles of water, and at 200° 9. it retains only 1 mole cf water of hydration. Recent chemical handbooks (7d, 120) describe this compound as being insoluble in hot and cold water-, but coluble in acids and ammonium chloride, 5, Easic magnesium orthoa.rseno.tes Ear stow and Cottringer (9) patented a method of making magnesium arsenate insecticide which they believe produces two basic magnesium arsenates. To one of the compound's they assign the formula MggCAsO^g.MgO.YiLgO., in which the value for (Y) was not determined. This compound occurred either as long needle-shaped crystals; as elongated pointed^-end crystals; or as short, flat prisms, having parallel extinction and a' positive principal zone, with /Vm = 1.530 and 7k 1.605, To the other basic compound they gave the formula Mg3(As04)2.2MgO.ZE20, in v/hich (Z) represented the moles of water of crystallization, but was not determined. This compound occurred as exceedingly small lens-shaped crystals, having parallel extinction and a positive principal zone, with/fcf = 1.566 and Vj y, = 1.575. - 6 - 6. Magnesium ammonium or tho arsenate .. This compound crystallizes in tetragonal prisms with 6 moles of water of hydration. Its formula .is Mg3SJE4.AsO4.6HoO. It may he prepared in a number of ways (41, 62, G4). It is precipitated under ordinary con- ditions when arsenic acid or a water- soluble arsenate- is added to a solution of a water-soluble magnesium compound, in the presei.ee of ammonium chloride, and- ammonium hydroxide. It i-s a white compound (62, 75, 120), having a density, of 1.932 g/cc at 15° C; 0.03B part is soluhle in 100 parts of water at 20o C. It is soluble in hot- water and in acids, hut in'soluhle in alcohol. When ignited it is converted into the magnesium pyr oar senat e (Mg^AsgOy ) . 7. Douhle salts of magnesium arsenate (62, 96). Magnesium orthoarsenate forms douhle salts with other elements, hut their properties and method of preparation will not he descrihed in this circular, G. Patented Methods of Preparing Magnesium Arsenate Insecticides The first United States Patent issued for the manufacture of magnesium orthoarsenate as an insecticide was. issued to Bar stow (8). This patent covered "both the di- and tri-orthomagnesium arsenates. The compounds were produced hy the reaction of arsenic acid on magnesium hydroxide in the proper proportions, or hy the reactions of the normal and acid arsenates with the water- soluble salts of magnesium. Dow (43) a little later took out a patent for the manufacture of an insecticide consisting of a mixture of lead and magnesium arsenates.. . . The product is formed hy reacting a suitahle lead salt with an excess of arsenic acid, and neutralizing the residual acid with an excess of magnesium hydroxide. Dow (44) patented the manufacture of diraagnesium arsenate as. an insecticide. He formed the product hy the reaction "between magnesium hydroxide and arsenic acid. Bar stow and Cottringer (9) made an improvement in the manufacture of magnesium arsenate as an insecticide, producing therehy a product in which the content of water-soluble arsenic (AS2C5) is claimed to he much lower than in ether magnesium arsenates. They precipitated the compound hy neutralizing a.rsehic acid with an excess of magnesium hydroxide, and subjecting this mixture to a temperature of approximately 145-175° C. in an autoclave under' pressure. They claimed that the magnesium arsenate may exist in' one "or all of three forms; first, the dimagnesium orthoarsen- ate, MgHAs04.XH20; second, the basic magnesium arsenate, Mg3(As04)2MgO.YH20; and third, another hasic arsenate, Mg3(As04)2«2MgO.ZH20. Cullen (34) patented a method of making a calcium or magnesium arsenate insecticide, in which he causes arsenious oxide (AS2O3) to react - 7 - with lime or magnesium hydroxide and roasts the arsenite so formed in a furnace, thus oxidizing it. By using an excess of lime or magnesium hydroxide, "basic arsenates are produced which contain less water- soluble arsenic than otherwise. The reactions involved may be illustrated by the following equations: MgO + As203 + H20 - Mg3(As03) 2 + H20 On roasting Mg3(A:;03)2 + 02 = Mg3(As.04)2 and 2Mg(0H)2 + As203 = :,ig2As205 + 2H2C on roasting Mg2As2C>5 + ^2 ~ ^'l€2^s2^7 Heath (73) improved upon Barstow' s patent (8) and the Barstow and Cottringer patent" (9) in producing a less soluble magnesium arsenate as well as improving its fluffiness. The product is produced by mixing a slurry of magnesium hydroxide in water with the reauired amount of arsenic acid solution. Then approx- imately 15 percent of caustic alkali equivalent to the arsenic acid used is added, as calculated from the molecular proportions in the following equation: (1) SNaOH + H AsO'4 -— >:Ta3AsC4 + 3H20 The resulting slurry is heated in an autoclave to 180° C, and held there until a sample on analysis shows less than 0.2 percent of soluble arsenic (As205). Seaton (134) patented an insecticide consisting of di- or tri- magnesium arsenate in which is incorporated approximr.tely 4 percent of a casein compound or an equivalent deflocculating agent, such as gelatin. D. Analyses of Magnesium Arsenate Insecticides Llagnesium arsenate as an insecticide was first offered for sale (122) in 1919. The early product contained 32.13 percent of arsenic oxide (As205) and had a water-soluble arsenic content of 1.25 percent (As205). This material caused severe injury to apple and peach foliage when applied as a spray. Patten (122) showed that the arsenic content of the early magnesium arsenate insecticide was rendered soluble in water "by the action of carbon dioxide. He determined the water-soluble arsenic content, using water saturated with carbon dioxide, and found that 41.7 percent of the total arsenic had gone into solution. By passing carbon dioxide for 2 hours through water (1,000 cc) in which magnesium arsenate insecti- cide (l gram) was suspended, he found that 96 percent of the arsenic oxide had been dissolved. Barstow and Cottringer (9) state that in practice when magnesium arsenate is made "by directly reacting magnesium hydroxide with arsenic acid, the product is apt to contain more arsenic in soluble form than is desirable. - 8 - Patten and O'Moara (123) in 1319 analyzed two samples of magnesium arsenate insecticides then on the market. One sample wa's magnesium orthoarsenate , while the. other simple -./as magnesium pyroarsenatc. The orthoarsenate contained 32.13 percent arsenic oxide (AS2C5) and had a water-soluble arsenic content of 1.25 percent (ASgQg) . The pyroarsonate contained 38.05 percent arsenic oxide (AS2O5) and had a. water- soluble arsenic content of 0.23 percent (As^Og) . They found that the water-soluble arsenic content of the pyroarsena.te, using water saturated with carbon dioxide, was only 3.0 percent (As205) , and when carbon dioxide was bubbled for 2-l/2 hours through water (1,000 cc) in which it (l gram) was suspended, only 11.28 percent of the total arsenic was rendered soluble. Cook and Mclndoo (2?) in 1922 made a ehor.ical, physical", and insecticidal study of the a.rsenica.1 insecticides on the market. Below are the results of their analysis on magnesium arsenate. Moisture Total arsenic (As q ) Water-Soluble arsenic (As^cO Magnesium oxide (MgO) Carbon dioxide (COg) Undetermined Leach (99) in 1925 analyzed a magnesium ar senate used in experiments as soil insecticides. Below are his results. 2.96 pe rcent 33.60 11 1.56 ti 34.32 11 0.5o 11 Pd.57 11 Total arsenic oxide (As Og) 44,33 percent Mg3(As04)2 equiv. to total As^Og 67.65 Water- soluble arsenic oxide (As^Og) 1.03 MgO in excess of arsenic oxide 8.43 Calcium oxide 1.98 ]?e203,Al203 i.20 Insoluble in acid (Si02) 0.68 Loss on ignition 20.06 Cathcart and' Willis (23) reported the total arsenic and the water-soluble arsenic contents of commercial magnesium arsenate insecticides on the market for the years 1930-1933 inclusive. Their results are tabulated below. - 9 - Magnesium arsenate Name of Year Total arsenic Water- soluble Guaranteed arsenic manufacturer Guaran- Found Found teed not (percent)not more (percent) less than thru (percent) (percent) Dow Chem. Co. 1930 20.90 20.86 0.23 0.07 ti ii ii 1931 20.90 20.60 0.23 0.23 it ii ii 1932 20.90 21.28 0.23 0.19 ti ii it ii 20.90 21.37 0.23 0.23 Mechling Bros. ii 20.90 21.33 0.50 0.23 Chipman Chem. Co. 1933 20.90 20.35 0.50 0.24 Dow Chem, Co. ii 20.90 22.31 0.23 0.12 Mechling Bros. it 20.90 21.45 0.50 0.19 Magnesium arsenate das t Dow Chem. Co. 1933 5.22 7.47 0.06 0.08 Dearborn (37) in 1930 made a more detailed analysis of commercial magnesium arsenates on the market. The methods of analysis used were those described in the A. 0. A. C. hook of methods (3). The results obtained are tabulated below. Magnesium arsenate Sample 1 Moisture Total arsenic (AsgOs) Wat or- sol. arsenic (As205) Water-soluble salts Arsenious oxide (AsgcO Acid insol. Alp0^, Fqo0~ Calcium oxide Magnesium oxide Cubic inches per pound pH value of 2/o susp. Percent Percent guaranteed found Sample 2 0.8 32.0 32.6 0.35 0.04 — _ wm 2.5 0.1 0.6 — 0.3 — 1.4 47.9 145 9.8 Percent Percent guaranteed found 0.7 40.0 41.0 0.35 0.10 r»— — 2.6 _-— 0.2 0.7 — 0.8 1.5 44.2 — _ 113 9.8 Dearborn in 1934 collected samples of magnesium arsenate insecticides and magnesium arsenate dusts for analyses. The results obtained are tabu- lated beiow. UBR&P r ^ATE PLANT BOARB - 10— Magnesium arsenate insecticides _ Ssmp:I e" : 1 Sample 2 Sample 3 Percent percent Percent Percent Percent Percent guaranteed found guaranteed found guaranteed found Moisture Total arsenic (A; Wat or- so ruble As Arsenious oxide Calcium oxide Magne s ium oxide Car ocn dioxide Insoluble in acid Loss on ignition 2V5 Oj 52.0 0.35- 1.09 33.09 32 . 0 0.29 0.50 none ~_ 1.96 — 45.6-1 — 1.04 — 0.18 — 16.39 — 1. ,36 38. ,17 0. none 1. ,96 46, ,99 0, , 83 0. ,10 17, ,01 Mexican "bean beetle destroyer Percent .Percent guaranteed found Moisture Total arsenic (AspOc) Arsenious oxide Water-soluble A32O5 Calcium oxide Magnesium oxide Carbon dioxide Loss 011 ignition Insoluble in acid — 0.13 8 . 00 10.24 — none 0.50 0.15 — 55.44 — 12.44 — 1.59 — 16.25 — 0. reported good control of the beetle in 1930, using magnesium arsenate. Cory, Sanders, and Eenerey (31) give a general account of the campaign carried out in Maryland in 1929 against the Mexican bean beetle. Tests of materials to determine whether they would render arsenicals less likely to injure the foliage showed an advantage from tne use of copper sulphate, lead monoxide, and zinc with calcium arsenate. Copper sulphate reduced injury both in dusts and sprays. Magnesium arsenate as a spray proved the most offective material for securing commercial control of the beetle. - 15 - Eddy and Clarke (50) in their circular consider that mag- nesium arsenate is the only arsenical that is effective in control- ling the Mexican dean dee tie and yet harmless to the plant. Howard (8G) in 1930 considered Magnesium arsenate, as a spray, the best known remedy for the protection of "beans against the Mexican dean deetle. Howard and Br anno n (87) doth consider that from the large number of remedies that have been tried, magnesium arsenate has given the "best control against the beetle. Knull (95) in 1930 recommended the use of magnesium arsenate for the control of the Mexican "bean beetle. If magnesium arsenate is not available, lead arsenate as spray or dust can be used. When used as a spray or dust, hydrate d lime is added. Greater injury to the bean plant was caused by calcium arsenate than by lead arsenate, List (101 ) in 1930 stated that in Colorado magnesium arsenate and zinc arsenite may be used safely on bean foliage, with good con- trol of the "beetle. Magnesium arsenate is more generally used in the eastern sections of the United States. Marlatt (105) in his yearly report stated that during 1930 experiments were conducted on attractants and repellents, using the Dean beetle in tests. Bean foliage sprayed with arsenicals was repellent, but not sufficiently so to prevent feeding. Lead arsenate was the most repellent, magnesium arsenate was less so, and calcium arsenate the least. Marlatt (.105) in 1930 reported that the results of further experiments with control measures agree closely with those obtained in previous years, and that magnesium arsenate is the best material to use for controlling the Me lean bean beetle. It did not injure bean foliage to any appreciable, extent in any of the sections where tested. Calcium arsenate resulted in injury in many instances. Lead arsenate caused heavy plant injury. Peairs (124) in 1930 mentioned the use of lead, calcium, and magnesium arsenates with lime as sprays or as dusts in controlling the Mexican bean beetle. Burdette (19) in 1931 tested several materials for the control of the Mexican bean beetle. Calcium arsenate in a large number of cases caused considerable injury to bean foliage. Magnesium arsenate caused no injury as a spray or dust and is recommended for control work. In 1931 the entomologist of the Connecticut station (140) drew conclusions from a study made in 1930 on the control of the beetle. He found that bean damage could be prevented by spraying or dusting combined with certain cultural practices. Spraying was - 16 ■- most effective when using magnesium arsenate with casein-lime. Friend and Turner (56) in 1931 stated, that the first material recommended for tlie "beetle control was paris green, but this injured the bean severely. Lead arsenate used in Colorado in 1921 and in New Mexico in 1907 was fairly satisfactory, although some damage resulted. Later investigations have shown that lead arsenate reduces, the yield of beans, in some cases up to 59 percent, even though no visible injury develops. Calcium arsenate was not quite so injurious; visible injury occurred in most cases, however. Magnesium arsenate caused no visible injury, but a reduction in yield occurred in three cases, one when the material was used alone, and the other two when diluted with hydrated lime. Hedrick (74) in 1931 stated that the Mexican bean "beetle had been known on Long Island since 1928. Experiments were commenced in 1930 to determine the relative value of recommended spray and dust mixtures, as indicated by the tolerance of bean plants to such sprays or dusts. It was foiind that both spray and dust mixtures containing lead or calcium arsenates were decidedly toxic to the plant. The burning effect was slightly reduced when the arsenical s were used with bordeaux mixture or copper-lime dusts. Magnesium arsenate and barium fluosilicatc appear to be noninjurious to the plants. Huckett (90) in 1931 made field tests with commercial brands of arsenicals, both as sprays and as dusts. Magnesiiam arsenate was the safest to use on bean foliage at the commonly recommended strengths. Lead and calcium arsenates caused considerable reduction in yield and serious injury to the foliage. Huckett (91) during 1931 conducted field tests with five ar- senicals to determine the amount of injury caused to hern foliage. They were applied as spray and as dust. Acid and basic lead ar- senate, calcium and magnesium arsenates, and zinc arsehite were used. Magnesium arsenate, both as snray and as dust, was the satisfactory material. Langford (97) in 1931 recommended the use of magnesium arsenate as a spray for the control of the Mexican bean beetle. Marlatt (106) in 1931 reported extensive tests conducted ?/ith barium fiv.osilicate, cryolite ,. and potassium fluoaluminate against the beetle. No conclusive results were obtained. The indications were that when used as dusts, these materials will not give such satisfactory control as docs magnesium arsenate or calcium arsenate, as they do not adhere to foliage as well as the arsenicals. Sherman (136) tested calcium and magnesium arsenates against the beetle. Magnesium arsenate gave the best results. - 17 - Swcetman (150) in 1931 recommended the use of magnesium arsenate as a dust or spray for the control ox the Mexican "bean "beetle. Bourne (11 ) in 1932 nade preliminary tests with various in- secticides for control of the Mexican "bean "beetle in Massachusetts. Magnesium arsenate either as spray or dust was found the safest and most dependable material on the market. Both lead and calcium arsenates caused severe "burning, in most cases killing the plant. Brannon' s (13) observati ons on the control of the Mexican bean "beetle on snap Deans, when heavily infested with the onion thrips, showed that magnesium arscrato caused plant injury, which was probably due to laceration of the e;oidc:.miis of the leaf by the thrips with subsequent entrance of the arsenical. If nicotine sulphate is added to the spray no arsenical injury results. Kuckctt (92) recommended in 1932 the following materials for the control of the Mexican lean beetle: Sprays Magnesium nrsonate, with Kay so or flour paste, or with skim milk and. hydratod lime. Calcium arsenate ,-,ith bordeaux mixture, or with hydratod lime. Dusts Magnesium arsenate with hydratod lime. Calcium arsenate with dehydrated copper sulphate and lime. Marlatt (107) in 1932 reported that magnesium arsenate as a spray remained, for most areas and conditions, the best means of controlling the beetle. Fluorine compounds do not give protection to the bean plant for so long a period as does magnesium arsenate. Sherman (13?) conducted further tests with magnesium arsenate for the control of the beetle. He showed that the arsencial is highly toxic to the beetle and at the same time has little or no injurious effects on the bean plant. Dusts were preferable. Sherman (138) in 1932 experimented with substitutes for magnesium arsenate in controlling the Mexican bean beetle. Conclusions were not drawn, but the cost of the substitutes was greater than that of magnesium arsenate. Turner (152) in 1932 found that magnesium arsenate was the most satisfactory material to use for the control of the beetle. - 18 - Eourne (12) in 1933 experimented with materials for controlling the "beetle. Manganar (manganese arsenate) with lime caused severe "burning of "bean foliage. Dutox ("barium fluosilicate) compound com-oared. favorably with magnesium arsenate, the standard material for controlling the Mexican "bean "beetle. Douglass (42) in 19-33 carried out experiments for controlling the Mexican bean "beetle in New Mexico. He used lead, calcium, and magnesium arsenates. In 1929 lead arsenate caused the greatest amount of injury, magnesium arsenate causing the least. In 1933, Howard, Brannon, and Mason (88) reported results of field tests on the control of the Mexican "bean "beetle, cover- ing a period of 3 years. They reported that there appears to "be no advantage in changing the current recommendations for the use of magnesium arsenate. Marlatt (108) in 1933 reported the continuation of field and laboratory tests in Ohio and Virginia against the "beetle. Fluorine compounds have not given satisfactory control when used, as dust'-. The use of magnesium arsenate, however, is still recom- mended. Turner and. Friend (155) in 1933 recommend.ed a spray con- sisting of 3 pounds of magnesium arsenate and. 2 pounds of casein-lime in 100 gallons water for controlling the Mexican "bean beetle. This mixture proved very satisfactory in 1933. Monohydrated copecr sulphate 19 percent, calcium arsenate 17 percent, and. hydrated lime 64 percent was the most satisfactory dur';. Turner and Friend (153) in 1933 reported further tests with materials for use against the Mexican bean beetle. A dust composed of monohydrated copper sulphate 19 percent, calcium arsenate 17 percent, and hydrated. lime 64 percent, proved highly satisfactory. It was superior in control to magnesium arsenate, but was more expensive. For spraying.,: magnesium arsenate with casein-lime is recommended.. For dusting, the above mentioned copjjcr-arscnic-lime mixture, magnesium arsenate with line, or barium fluosilicate with hydrated lime arc recommend.ed. Turner and Friend (154) in 1933 recommended the use of a spray consisting of magnesium arsenate .and calcium caseinate for the control of the beetle. Huckett (93) in 1934 successfully used dcrris dusts as a substitute for magnesium arsenate in the control of the Mexican bean beetle on snap and lima beans during the period of pod forma- tion. *- 19 -» 2. Bean leaf beetle (Ccrotona trifurcata (Forst.)) Eddy and Nettles (51) report work done on the control of the "bean leaf "beetle. Calcium arsenate and magnesium arsenate were used in experiments conducted at Clemson College. In these tests calcium and magnesium arsenates were -about equally effective in controlling the adult insect. Magnesium arsenate is recommended as a spray or dust in control measures. 3. Codling moth (Carpocapsa pomonella (L.)) Sanders (131) in 1919 stated that russeting of apple fruit due to bordeaux mixture may be avoided by the addition of lime. In ITova Scotia, russeting is prevented by using calcium or magnesium arsenate in place of bordeaux mixture as a spray. Dutton (46) in 1920 made a comparison of various sulphur- arsenate dust mixtures c£ leadarsonate , calcium arsenate, and magnesium arsenate. These materials were used on apple, cherry, plum, peach, currant, and potato foliage. Load arsenate was recommended for general use on all kinds of fruits, as it had given uniformly better results than any other arsenate. Calcium arsenate gave excellent results when used on potatoes and other similar crops, but was not always satisfactory on fruit trees. Magnesium arsenate caused severe foliage injury on peach and apple and failed to give satisfactory control of the codling moth.. Halligan (67) conducted tests in 1920 to determine the com- parative value of numerous arsenical compounds for controlling the codling moth. Lead arsenate proved to be the standard material for fruit spraying. Calcium arsenate, even with the addition of lime, caused severe foliage injury to apple and peach. Magnesium arsenate also proved unsatisfactory. Melander's (109) investigations into the best treatment for controlling the codling moth showed that calcium arsenate is inferior to lead arsenate, and magnesium arsenate still inferior to calcium arsenate. Fernald and Bourne (53) in 1922 found that calcium metarsenite, magnesium arsenate, and zinc arsenite were unsafe to use on fruit tree foliage. Melander (110) in 1923 reported results of spraying experi- ments against the codling moth. Calcium and magnesium arsenates were inferior to lead arsenate. ' Slightly better resxilts were obtained when calcium caseinate was added. - 20 - Newcomer, Yothers, and Whit cor. Id (119) in 1924 stated that magnesium arsenate, calcium arsenate, and Paris green have been "used as codling moth sprays, hut are not so desirable or so safe on the foliage as load arsenate. Howard- (81) in 1927- reported the use of substitutes for lead arsenate in orchard spraying, which included magnesium arsenate. Spuler (144) in 1927 conducted experiments against the codling moth with lubricating and drying oils to determine the value of the. latter as an adhesive for arsenical sprays, the value of lubricating oil as a combined adhesive end ovicide, and the possibility of substituting lubricating oil for lead arsenate. Fish oil was combined with calcium and magnesium arsenates. The result obtained by combining fish oil was better than when- calcium or magnesium arsenates was used alone, but their toxicity was not so good as obtained, with lead arsenate. Alden and. Yeomans (2) in 1928 experimented with non-lead arsenical sprays for controlling the codling moth. All gave poor results when compared, to lead arsenate, and most of them injured the foilage severely. Magnesium arsenate gave the best results of the now sprays, In the report of the committee of econc. .c entomologists (126) to formulate plans for investigating the codling moth (published in _ 1928) a summary of 4 laboratory and 32 field tests showed that magnesium arsenate was about one-half as effective as lead arsenate in controlling the pest. Severe injury to the foliage was recorded in several cases. Howard (82) in 1928 reported that the compounds tested against the codling moth v/ere considerably less effective than lead arsenate, and that some caused important foliage injury. Magnesium arsenate was one of the a-rsenicals used. Experimental work was conducted, in 1928 at the Washington Station (145) on codling moth control in Which the arsenates of manganese, calcium, and magnesium rvere used. None proved as efficient as lead arsenate. Newcomer and Yothers (118) conducted a series of laboratory a.nd orchard experiments in controlling the codling moth over the period 1919-29, The arsenates of lead, calcium, and magncsiiam were tested. None of the arseniCals tried in these tests in the laboratory equaled lead ars.cnato. i- - 21 - Spoiler (146) in 1929 tested a series of arsenical s against bhe codling moth. The arsenates of calcium, magnesium, manganese, and aluminum were used. Calcium and magnesium arsenates gave such poor results that tests were discontinued, at the end of the first "brood of the codling moth. Talbert, Hooker, and Startwout (151) tested in 1929 various sprays for the control of the codling moth. They ^ound that magnesium arsenate defoliated peacn trees, out only slightly in- jured apples in general and controlled the codling moth and plum curculio as well as did lead arsenate. Jonathan and Ingram apples suffered considerable burning from magnesium arsenate. Peairs (124) tested, promising insecticides in 1931 to find a substitute for lead arsenate. The insecticides tested included calcium and magnesium arsenates. The best results were obtained with magn e s ium ar s ena t e . Prist (57) in 1932 reported the results obtained from spraying and dusting experiments carried out in Pennsylvania over a period of 8 years on apples. He reported that slightly less injury oc- , curred in spraying than in dusting experiments. Calcium and mag- nesium arsenates were found to be as effective as lead arsenate. Magnesium arsenate combined with lime-sulphur caused no injury to foliage. Garman (52) carried out some experiments in 1933 on apple and peach trees. The arsenates of calcium, manganese (manganar) , magnesium, and zinc were used. Magnesium arsenate caused severe foliage injury to apple trees. The data were not extensive enough to warrant conclusion:;. On peach, magnesium arsenate caused severe d.cfolia.tion, fruit drop, and bark canker. Harma,n (70) conducted experiments in 19. 3 in western New York v/ith five cover sprays of various material s against the codding moth. The materials tested included lead, calcium, and magnesium arsenates. The: most effective mat .rial was lead arsenate which gave 80 percent uninjured fruit. Calcium arsenate with bordeaux mixture caused considerable yellowing end dropping of foliage. All of the arsenicals left a. residue in excess of permitted tolerance. Washing for 25-30 seconds in 1 percent hydrochloric acid solution at 59° C. , within 2 weeks after picking, effectivoiy rceluced arsenical residue, except on apples sprayed with manganese, magnesium, and lead arsenates. Outright (35) in 1934 tested five arsenicals against the codling moth on apples. Load and magnesium arsenates were the lea.st toxic to the foliage, but the latter gave poor control of the insect. Flint (55) in 1934 reported that Hutson in Michigan experimented with calcium, zinc, and magnesium arsenates for controlling the codling - ?9 . notL. They gave lower control than lead arsenate, and were not in- jurious to vigorous trees. In Ohio they made field tests' and reported their efficiency in the following order: Lead, zinc, calcium, and magnesium arsenates. • '■'.:..' Parrott (121) in 1934 conducted experiments with the most promising insecticides for controlling the codling moth in New York. lead, calcium', and magnesium arsenates were used. Lead arsenate, alone or with oil, proved to be the most effective. When tested in the orchard, none gave as good results as lead arsenate. The poor control of the nonlead arsenical s and the relatively high degree of injury resulting from their use practically eliminated all of them from further consideration. Spuler (147) in 1934 found that the addition of a semi- drying oil, such as fish oil, increases the efficiency of calcium and magnesium arsenates, which when used alone have not been satis- factory for controlling the codling moth. 4. Plum curculio (Conotrachelus nenuphar (Herbst)) Snapp (143) in 1928 made a study of the toxic value of a.rsenicals and fluosilicates on the plum curculio. Lead, calcium, and Magnesium arsenates were used. Lead arsenate Was more toxic than the other arsenates, the toxicity being in the following order: Lead, calcium, and magnesium arsenates. Talbert, hooker, and Startwout (151) in 1929, in testing various sprays, found that magnesium arsenate defoliated peach trees, but that it was only slightly injurious to apples in general and controlled the codling moth and the plum curculio as well as did lead arsenate. Jonathan and Ingram apple trees suffered considerable burning from the use of magnesium arsenate. • Studies in Connecticut (141) on substitutes for lead, arsenate in 1933 revealed, the fact that magnesium arsenate caused severe burning of peach foliage. The best control of the curculio. was obtained with lead arsenate with zinc sulphate corrective. Howard (81) in 1927 reported that extensive tests were made in Georgia to determine the relative toxicity of a number of arsenicals to the plum curculio on peach. The arsenates of tri-calcium, barium, ana zinc, in the order named, were found rather toxic to the insect. The arsenates of magnesium, manganese;, and aluminum were less toxic. Howard (82) in 1928 reported that in Georgia tests were made to determine the toxicity of a number of arsenicals against the plum curculio. Laboratory studies wore completed, on the effects of hydrogen-ion concentration upon the arsenates of acid lead, tri- calcium, and magnesium. Considerable correlation had. been found to - 23 - exist between the burning produced upon peach foliage and the speed with which these arsenates decompose in a solution having a pH equal to that of rain water or dew. 5. Japanese beetle (Popillia japonica (Newm. )) Leach (99) in 1926 discovered that the larvae of the Japanese, beetle died when they fed in soil containing a sufficient amount of certain arsenates. He experimented with the. basic and acid arsenates of lead, magnesium, and calcium. The basic arsenates of lead and magnesium were found to be nontoxic to the larvae as well as to the plants. Van Lecuwen (158 ) in 1932 tested a number of materials in the field for repelling the Japanese beetle. The materials tested were acid lead arsenate, acid lead arsenate mixed with other materials, basic lead arsenate, magnesium arsenate, and calcium arsenate. Foliage strayed with water was used as a check. A larger number of beetles left the trees sprayed with magnesium arsenate than from the unsprayed trees. Marlatt (106) in his report for 1931 says that experiments were conducted to determine whether stomach poisons would be effective insecticides against the Japanese beetle larvae, when introduced into the soil. Certain fluosilicates are effective when freshly applied, although much slower in action than acid lead arsenate. Magnesium arsenate was found to be almost equally effective. Basic lead arsenate proved to be of little value. The insecticide! action of the arsenates was only slightly lessened after being in soil for 1 year. 6, Rusty tussock moth (Notolophus antiqua (L. )) Crowley (32) conducted experiments on controlling cran- berry insects in 1927-28. He discovered that magnesium arsenate was much superior to lead arsenate as an insecticide against the tussock moth. Crowley (33) in 1929 carried on further experiments with magnesium arsenate. He found that the tussock moth was controlled ~oy magnesium arsenate, which proved to be a very efficient spray. Julmek (58) in 1929 made a study of the differences in toxicity of various arsenical insecticides, in Sumatra, on a number of caterpillars. Toxicity did not correspond with the percentage of arsenic oxide in the samples. In practice the following sequence was observed: Paris green, lead, calcium, zinc, and iron arsenates. Feeding experiments in Austria in 1927 with the caterpillars of Pieris brassicae L. revealed similar discrepancies. In 1928 tests were made with six arsenites and six arsenates on caterpillars of Notolophus antiqua (L. ), G-astropacha quercitolia (1. ), and Pieris brassicae (L.) In sequence of killing power the arsenites were magnesium; then lead, calcium, and copper of the same toxicity; iron, - 24 - and zinc. The arsenates were lead, copper, calcium, magnesium, zinc, and iron. The toxicity of the arsenites was superior to that of the arsenates. 7. Cranberry fireworm (Phopobota vacciniana (lack.)) Crowley (33) in 1927-28 experimented with magnesium arsenate spray in controlling the cranberry insect. It was found superior to lead arsenate, "but doubt was expressed whether it could "be used alone as a fireworm spray. 8. Potato flea-beetles (Spitrix cucumeris Harris and E. subcrinita Leconte) Hanson (69) conducted experiments with numerous arsenicals and nonarsenical materials in controlling the potato flea-beetle. The arsenicals used were calcium and magnesium arsenates and both acid and basic lead arsenate. The best control was obtained with calcium and a.cid lead arsenates, used as a dust and mixed with lime. Calcium arsenate was the most effective arsenical when used cither as a dust, a spray, or in combina.tion "1th bordeaux. Daniels (36) in experiments with the flea-beetle used calcium and magnesium arsenates. Both spray and dust experiments were made. The results with magnesium arsenate were discouraging, with no tubers entirely free from worm tra.cks. 9. Oriental pea.ch moth (Crapholitha molesta (Busck)) Peterson (125) in 1920 tested a number of arsenicals on peach folia^ge and twigs in experiments on controlling the peach moth. The arsenates of lead, calcium, and magnesium were used as sprays and dusts. None of the arsenical sprays stopped the larvae from entering the twigs. When the arsenicals were applied as dusts, the calcium and magnesium arsenates, alone or in com- bination with lime, killed approximately the same percentage of the larvae as did lead arsenate. 10. Boll weevil (Anthonomus grandi s (Boh.)) Walker and Mills (159) in 1927 tested over 100 poisons and poisonous mixtures against the cotton boll weevil in the laboratory. Magnesium and zinc arsenates showed weevil toxicity about equal to or greater than calcium arsenate, and caused little or no plant injury. 11. Cabbage insects Fulmek (58) in 1929 determined the toxicity cf a number of arsenates and arsenites, using the caterpillars of the cabbage moth and the leaf weevil. The order of the toxicity of the arsenates was found to be lead, copper, calcium, magnesium, zinc, and iron. .The arsenites were in the following order: Magnesium, lead, calcium - 25 - copper, iron, and zinc, Reid (123) in 1934 Rested numerous materials against, the cabbage loopcr (Autographa bra^sicae (Riley)), the diamond-back moth (Plutella maculipennis (Curtis)), and the imported cabbage worm (Ascia rapae (L.)). Calcium and magnesium arsenates were not so toxic as derris and pyre thrum powders. IS. Strawberry root weevils ( 3 rachy rhi nus o vat" a s (L. ) and 3. rugiirons ( Gyll . ) ) Icelander and Spuler (ill) in 1226 tested various poison baits. Calcium, magnesium, and lead arsenates, paris green, white arsenic, sodium fluoride, and paradichlorobenzone were used. Of these materials, magnesium arsenate proved most satisfactory. Melander, Webster, and Spuler (112) in 1926 investigated soil treatment for controlling the strawberry root weevils. The materials used were the arsenates of magnesium, calcium, and zinc; and sodium fluoride. Magnesium arson:. te proved to be the most toxic to the weevils. Downes (45) in 1927 experimented with a poisoned apple-waste "' t against the strawberry root "./-evils. He used sodium fluo- silicate and calcium and magnesium arsenates. All gave good results. Mote and Wilcox (117) in 1927 experimented with poison bait in controlling the strawberry rootweevils. Extensive field and laboratory tests were conducted in order to determine which poison would give the best results under varying conditions. The arsenates of calcium, lead, and magnesium wore used. Calcium arsenate was found to be the most effective in the tests. Urbahns (157) considers magnesium arsenate unsafe for spray- ing upon foliage, but states that it is coming into more general use in connection with poison bait for the control of strawberry root weevils, and possibly other forms, such as the vegetable weevils. 13. Beet webworm (Loxostegc sticticalis (L.)) Gillette (60) in 1913 reported experiments with paris green, and calcium, lead, and magnesium arsenates on controlling the webworm of the sugar beet. All these materials were satisfactory when applied in double the ordinary strength used for controlling ordinary leaf-eating caterpillars. Gillette and List (6l) in 1920 successfully controlled the webworm on sugar beet's by spraying with calcium, magnesium, and lead arsenates. - 26 - 14. Turnip webworm Bo'binson (130) in 1931 reported the use of 13 materials in tests to determine the' best control of the turnip webworffi. Five material?, including lead and calcium arsenate, when applied as a dust gave 100 percent kill of the larvae. The mortality from the other materials dusted, which included magnesium arsenate, were so low that no further tests were made with them. They wore tested as sprays and proved valueless. 15. Spotted Dlister beetle (Epicauta maculata (Say)) peairs (124) in 1331 found that magnesium arsenate applied £is a dust or spray gave good control of tno blister beetle 5pic.au.ta maculata on the fruit trees. 16. Black vine weevil ( Bra chy rhi nus sul c a tus (E. )) Smith (142) in 1927 made a study of the contaol of the black vine weevil in greenhouses and nurseries. lead arsenate as a soil insecticide offered some promise. Poisoned dried-apple waste baits containing 5 percent magnesium arsenate or lead arsenate were tested without much success. 17. European corn borer (Fyrausta, nubilalis (Kbn. ) ) Caffrey and Worthley (20) in 1922 concluded that the appli- cation of arsenical poisons had. not been found to protect growing corn plants from injury -"by the European corn borer. Lead, calcium, and magnesium arsenates were tested. Caffrey and Ku'oer-(2l) in 1928 reported experimental work covering 5 years. The materials tested alone or in various combinations as sprays or lusts were lead, calcium, and magnesium arsenates. No materials were recommended by them for practical use. 18. Blueberry maggot. (P-hag*. letis pomonella (Walsh)) Lathrop and Nickels (98) in 1932 reported dusting experi- ments with lead, calcium, and magnesium arsenates against the blue- berry maggot in Maine.. 19. Squash beetle (Soilachna boreal is (P.)) Underhill (156) in 1323 experimented with calcium, magnesium, ana lead arsenates in the control of this beetle, feeding on watermelons, Calcium arsenate gave the best control. All the compounds had a more or less repellent action. The larvae are more su.-.cptiblo than the beetle to the poisons. - 27 - 20. plum web-sawfly ( I" euro toma inconspicua (Norton)) Severin (135) in 1920 conducted spraying experiments with stomach and contact poisons on the control of the plum web-sawfly. The stomach poisons were much more effective. Calcium and magnesium arsenates caused considerable scorching to the trees. Lead arsenate gave satisfactory control; it was also effective as a dust. 21» Grapeberry moth (Polychrosis viteana (Clem.)) Howard (76) in 1921 reported the use of arsenical sprays against the "berry moth feeding on grapevines. Calcium arsenate can "be used on Concord grapes but burns the leaves of most other varieties. Magnesium arsenate is more injurious than lead arsenate, and can not be used on grape foliage. Howard (77) in 1922 reported the use of calcium and magnesium arsenates on grape foliage for controlling grape insects. They are not so safe to use as lead arsenate on the foliage. Howard (82) in his report for 1928 says that sprays of calcium and magnesium arsenates have been tested against grapevine insects. The results of experiments in 1927 show that the arsenates of calcium end magnesium give the same control cf the berry moth as does lead arsenate. 22. Green clover worm (plathypena scabr.a (P.)) Stirrett (148) gives the history and bionomics of this noctuid in North America. The first outbreak in Canada was in 1931. Control measures consisted in dusting or spraying with calcium or magnesium arsenate. Beneficial results were obtained in most cases, with no reports of foliage injury. 23. The pyralid Maruca t.estulalis (Geyer) Bruner (16) in 1931 described -,he larva, pupa, and adult of this pyralid, which burrows into p^as of lima beans in Cuba. Spray- ing with a mixture of lead arsenate and bordeaux mixture is far from satisfactory, Magnesium arsenate may prove more suitable. 24. Colorado potato beetle (Leptinotarsa dcccmlincata (Say)) Couturier (54) in 1933 experimented with sprays against the potato beetle. It was found that, based on an equal content of arsenic pentoxide, copper and aluminum arsenates were nearly as toxic as lead arsenate, and magnesium arsenate was more so. Pernald and Bourne (52) in 1919 made experimental spraying tests with lead, calcium, and magnesium arsenates, in combination with bordeaux mixture, on potatoes to control insects. The three arsenicals appeared to be equally good. 25. Red-1 egged grasshopper (Melanoplus f '. :mur-rubram (Leg.)) Ma.rcovitch and Standi 07 (103) in 1929 experimented with bran baits containing 0.5 percent' "by weight of various poisons against the red-legged grasshopper. The percentage of mortality obtained, in 30 hours with the materials was: barium fluosilicate, 95 percent; sodium fluosilicate, 100 percent; magnesium arsenate, 0 percent. 26. Lima, bean pod borer caterpillars (Ma. rue a testulalis (G-eyer), Fundclla cistiponnis (Dyar), and Etiella zinck- encll'a '(Treit. )) Wolcott (161) in 1935 gave- notes on the bionomics of the lima bean pod borers in Puerto Rico. Experiments with sprays of bordeaux mixture, with or without magnesium arsenate, failed to reveal any promising method of control. 27. Gypsy moth (Porthetria dispar (L.)) Marlatt (106) in 1931 reported that various insecticides were used to ascertain to what extent they were, toxic to the gypsy moth caterpillars". Laboratory tests were conducted, using sprigs- of foliage treated with the different poisons. With the lethal dose as a standard, the toxicities of the materials wore as follows: lead arsenate, 100 percent; calcium arsenate, 100 p-'cent; magnesium arsenate, 50 percent. 28. Miscellaneous- Austin (4) in 1927 reported the results of experiments with insecticides under Ceylon conditions. Lead and magnesium arsenates were used. -29- Literature Cited 1. Abegg, P. Handbuch der anorganischen Chemie. Vol. 3, pt. 3. 1907. (See pp. 540-542.) 2. Alden, C. H. , and Yeomans, M. S. Codling moth control in Georgia apple orchards. Jour. Econ. Ent. 21: 319-324. 1928. ■ 3. Association of Official Agricultural Chemists. Official and tentative methods of analysis. Ed. 3. 1930. (Magnesium arsenate, p. 47.) 4. Austin, G. D. Preliminary notes on the toxicity of some standard insecticides under Ceylon conditions. Ceylon Dept. Agr. Yearbook, pp. 49-53. 1927. 5. Barre, H. 71, Mexican jean "beetle. 37 Ann. Ppt. S. C. Agr. Expt. Sta. , pp. 45-46. 1924. 6. Barre, K. W. Investigation in insecticides. 41 Ann. Ppt. S. C. Agr. Expt. Sta., pp. 52-54. 1928. 7. Barre, K. W. Studies of insect pests. 42 Ann. Ppt. S. C. Agr. Expt. Sta., 1928-1929, pp. 57-70. 1929. 8. Bars tow, E. 0. Method of making magnesium arsenate, U. S. Patent Wo. 1,344,018. Piled Sept. 16, 1918; issued June 22, 1920. 9. Barstow, S. 0. , and Cottringer, P. Insecticide and method of making same. U. S. Patent No. 1,466,983. Piled Sept. 1, 1920; issued Sept. 4, 1923. 10. Blare z, Ch. Satu.ro.tion de l'acide arsenique normal par la magnesie, et formation de 1'a.rseniate ammoniaco-magnesien. Compt. Rend. 103: 1133-1137, 1886. 11. Bourne, A. I. Investigation of materials which promise value in insect control. Ann. Ppt. 1932, Mass. Agr. Expt. Sta. , Bull. 293: 28-30. 1933. 12. Bourne, A. I. Investigation of materials which promise value in insect control. Ann. Ppt. 1933, Mass. Agr. Expt. Sta. , Bull. 305: 31-32. • 1934. -30- 13. Brannon, L. W. Observations of the association of thrips with arsenical injury on snap beans. Jour. Econ. Ent. 25: 1112-1113. 1932. 14. Britton, W. E. The Mexican bean beetle in Connecticut. 29 Report Conn. State Entomologist" (1929) . Conn. Agr. Expt. Stc, Bull. 315: 531-585. 1930. 15. Britton, W. E. Distribution of Mexican bean beetle in ConnecMcut. 30 Report Conn. State Entomologist (1930). Conn. Agr. Expt. Sta. , Bull. 327: 577. 1931. 16. Brunei-, S. C. Inforrao del departamer.to do entomologia y fitopatologia 74 pp. Estac. Expt. Agron. , Santiago de las Vegas, Cuba. March 1931. "17. Burdette; R. C. . ; The Mexican bean beetle. 50th Ann. Ept. N. J. Agr. Expt. Sta., pp. 180-184. 1929. 18. Burdette, R. C. , The Mexican bean beetle. 51st Ann. Rpt. N. J. Agr. Expt. Sta. , p. 169. 1930. 19. Burdette, R. C. The Mexican bean beetle. 52d Ann. Rpt. N. J. Agr. Expt. Sta., p. 199. 1931. 20. Caffrey, D. J., and lorthley, L. H. : The European corn borer and its control. U. S. Dept. Agr. , Farmers' Bull. 1294. 1922. (See p. 35.) .'■ 21. Caffrey, D. J., and Huber, L. L. • The fundamental phases of European corn borer research. Jour. Econ. Ent. 21: 104-107. 1928. 22. Carter, ' R. H. " ' Compatibilities of insecticides, I. Eluosilicates and cryolite with arsenates. Jo\ir. Econ. Ent. 22: 814-618. 1929. 23. Cathcart, C. S. , and Willis, R. L. Analyses of materials sold as insecticides and fungicides during 1930-1933. N. J. Agr. Expt. Sta. Bull. 513: 5, 1.930; Bull. 530: 6, 1931; Bull. 548: 6, 1932; Bull. 556: 7, 1933. 24. Cecil, R. The Mexican bean beetle. N. Y. State Agr. Expt. Sta. Circ. 95. 1927. Geneva. -31- 25. Chapman, P. J. , end Gould, G. Z. The Mexican bean beetle in eastern Virginia. Va. Truck Expt. Sta. Bull. 65. 1928. 26. Chevron, L. , andDroixhe, A. Sur quelques phosphates et arseniates doubles. Bull. l'Acad. Roy. des Sci. , Lett, et Beaux-arts de Belgique (3rd sor.) 16: 473-493. 1886. 27. Cook, P. C. , and Mclndoo , N. Z. 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