Screening Tests with Materials Evaluated as Insecticides, Miticides, and Repellents at the Orlando, Fla., Laboratory, April 1942 to April 1947, 1947; E-802, A Digest of In- The Inorganic formation on Toxaphene, by R. C. Roark. 1950. In Advances in Chemistry, volume i: Insecticides Organic Phosphorus Insecticides, by S. A. Hall, pages 150-159; Alkali-Stable ^ Poly- chloro Organic Insect Toxicants, Aldrin and R. H. Carter Dieldrin, by R. E. Lidov, H. Bluestone, S. B. Soloway, and C. W. Kearns, pages 175-^^3- 195O' Inorganic insecticides are of mineral In Chemistry and Industry: The Gamma- Isomer of Hexachlorocyclohexanc (Gam- origin, mainly compounds of antimony^ mexanc), by R. E. Slade, volume 40, pages arseniCj barium, boron, copper, fluo- 314-3^9- 1950. rine, mercury, selenium, sulfur, thal- In Science in Farming, Yearbook of lium, and zinc, and elemental phos- Agriculture 1943-1947: The Chemistry of phorus and sulfur. DDT, by H. L. Haller and Ruth L. Busbey, pages 616-622; Pests That Attack Man, by Antimonyl potassium tartrate, tar- E.F. Knipling, pages 632-642. 1947. tar emetic, K(SbO) G,H,Oo.i/2TLO, N. Y, State Flower Growers Bulletin 7, is a white powder soluble in water. It Revised Recommendations for Azobenzene, is sometimes used as the toxic agent in by W, E. Blauvelt, pages 15-16. 1946. ant poisons and for the control of United States Patents: 2,291,193, Insecti- cide, patented by Lloyd E. Smith, July 28, thrips. 1942 (U. S. Patent Office Official Gazette, Arsenical compounds are the most volume 540, page 827): 2,010,841, Chlori- widely used inorganic insecticides. nation, patented by Harry Bender, August Recommendations for their use date ^3> ^935 {volume 457, page 302). from 1681. They were probably used before that. The poisonous properties of arsenic trioxide were well known during the Middle Ages and it was a favorite instrument of murder as prac- ticed by the Borgias. This knowledge of the poisonous properties of arsenic compounds probably led to their use as insecticides. Arsenic trioxide, As^Os, also called arscnious oxide, is a wdiite crystalline material sometimes referred to as white or gray arsenic. It is the starting material in the manufacture of arseni- cal compounds used as plant insecti- cides and it is sometimes used in weed killers. It is obtained from the flue dust from copper smelters. Our supply comes from domestic and foreign sources. It is sometimes used as the toxic agent in baits to control grass- hoppers, cutworms, and other insects. The calcium arsenate that is sold commercially as an insecticide is not a single chemical compound but a com- This cylindrical fungus-feeding beetle is plex mixture of several calcium arsen- admirably suited for \i\'mg in round tun- ates and an excess of calcium hydrox- nels which it bores into forest trees for the> ide. The material is made from arsenic propagation of its food. trioxide by first oxidizing it to arsenic 218 The Inorganic Insecticides 219 pentoxide with nitric acid and then Both forms should contain very little reacting the solution of arsenic pen- water-soluble arsenic pentoxide in toxide or arsenic acid with a slurry of order to minimize plant damage. Gen- calcium hydroxide. The conditions of erally they are much less aptto burn temperature, concentration, and dura- plant fohage than is calcium arsenate tion of reaction are important because or paris green. The basic compound is of their influence on the physical na- safer to use on growing plants in some ture of the product. Commercial cal- localities (for example, the foggy re- cium arsenate generally is colored pink gions of California) than is the acid and is alkaline in reaction. It is a finely compound, but in general it is not so divided powder. It has been used ex- toxic to insects. tensively against certain insects affect- Acid lead arsenate is used exten- ing field crops, especially cotton. It can- sively to control chewing insects on not be used safely on apples, peaches, fruits, such as apple and pear, on beans, and some other crops because flowers, trees, and shrubs, and on vege- of its burning efí'ect on the foliage and tables, such as potato and tomato. It fruit. also has extensive use in treating soil Calcium arsenate-calcium arsenite to control Japanese beetle and Asiatic mixture is sold under the name london garden beetle larvae and related soil- purple. It has some use for poisoning infesting forms. insects on cotton. A number of United States patents Among the insecticidal materials cover processes for the manufacture of containing copper and arsenic, copper- magnesium arsenates for use as insec- aceto-arsenite (or paris green), 3 Cu- ticides. The magnesium arsenates (AsO,)2.Cu(C,H,0,),,'is by far the tested as insecticides consisted gener- most important. It has been used as an ally of the dimagnesium arsenate, insecticide since about 1870. For many MgHAsO^, the trimagnesium arsenate, years it was the most widely used insec- Mg3(As04)<,, or the pyroarsenate, ticide in the United States for control Mg2As^07, with varying amounts of of Colorado potato beetles. It has water of crystallization and excess mag- largely been supplanted by some of the nesium oxide or hydroxide. newer materials, but approximately 4 Magnesium arsenate has been tested million pounds are used annually by against a large number of insects af- farmers and gardeners. fecting fruits and vegetables and at one Copper arsenite, Cu-^iAsO.,) 2.XH2O; time was recommended for the control copper meta arsenite, Cu(As03)2- of the Mexican bean beetle, but its use H2O; and basic copper arsenate, Cu.r has declined. (As04)2.Cu(OH)2, have all been pro- A crude manganese arsenate once posed as insecticides but have not been was proposed as an insecticide for com- used to any extent. Compounds similar batting caterpillars on tobacco because to paris green made from organic acids its brown color made it less conspicu- other than acetic have also been tested ous on cured tobacco leaves than the but have not developed into commer- white lead arsenate. cial use. Sodium arsenite is formed by dis- Several chemically different com- solving arsenic trioxide in sodium pounds are known as lead arsenate. hydroxide solution. Depending on the Two of them are commonly used as in- ratios of the reacting materials, the secticides. Acid lead arsenate (dilead- products range from the monosodium ortho arsenate), PbHAsO,, is formed compound, NaAsOg, to the trisodium by the action of arsenic acid on litharge arsenite, Na;{AsO;i. A standard for- salt. It is a white powder, insoluble in mula for making so-called liquid so- water. Basic lead arsenate (lead hy- dium arsenite requires 4 pounds of droxy arsenate), Pbi(PbOK) (As04)3, white arsenic and i pound of sodium also is a white insoluble powder. hydroxide per gallon of solution. 220 Yearbook of Agriculture 1952 Sodium arsenite is not used as an and flowering plants. It is sometimes insecticide on field crops because of its used also as an cmulsifier for lubricat- corrosive action. It is used as an in- ing-oil sprays applied to fruit trees, gredient in poison baits for grasshop- such as apple, pear, quince, and peach, perSj crickets, roaches, ants, and other when they are dormant. insects, and in stock dips. It has been Several other copper compounds, used extensively as a weed killer. including the oxide, oxychloride, phos- Zinc meta arsenite, Zn(As02)25 is phate, quinolinolate, silicate, basic sul- formed when a soluble zinc salt is re- fate, and cyanide arc used as spray acted with arsenious acid or white materials. They have little insecticidal arsenic under carefully controlled con- value but are potent fungicides. ditions, as it is soluble in either acid or Hydrated lime, or calcium hydroxide alkaline solutions. Ga(OH)2, is used in the manufacture Zinc arsenite is used in wood pres- of lime-sulfur, calcium arsenate, and ervation but is not used in household bordeaux mixture. When limestone, insecticides or as a constituent of CaCOy, is heated, the carbon dioxide formulations to be used on field crops. is driven off, leaving the product Zinc arsenate, Zn3(As04) 2, has been known as quicklime, CaO. When proposed in place of lead arsenate in quicklime reacts with water, heat is codling moth control, principally be- evolved and the resulting product is cause it avoids lead residues. hydrated lime, Ca(OH)2. Hydrated Arsenates and arsenites of many of lime is not primarily an insecticide but the other elements have been investi- is used as a safener with some of the gated for insecticidal use but none has arsenical sprays. been developed into satisfactory mate- Calcium cynanide, Ga(GN) '>> reacts rials. Organic arsenicals have likewise slowly with moisture in the air to liber- failed to find a place as insecticides. ate hydrocyanic acid gas, a highly toxic Barium carbonate, BaCOj,, is a organic compound used as an insecti- white, finely divided powder which is cidal fumigant. sometimes used as the toxic agent in rat Compounds that contain fluorine poisons. have been in use as insecticides since Borax, Na2B407, and boric acid, about 1890. Barium fluosilicate, H3BO3, have been used in roach pow- BaSiFß, a white, finely divided powder, ders, but more effective compounds, has been tested extensively as a substi- such as sodium fluoride, DDT, and tute for arsenicals in the control of chlordane, are available now. fruit and vegetable crop insects. It has Bordeaux, or bordeaux mixture, is some value in the control of flea beetles, the name applied to the compounds blister beetles, Mexican bean beetle, formed by reacting dilute solutions of and others.