Page 10 



BETTER FRUIT 



August 



inert, or less active, or ptiysically un- 

 suitable for use, but not necessarily in- 

 jurious to the host of the parasite. 



Class D, incompatible chemically and 

 also incompatible on account of in- 

 jurious properties ("therapeutically" 

 or "physically" or both). Dangerous 

 mixtures. Mixtures in which important 

 chemical changes occur and render all 

 or a part of the original constituents 

 injurious to the host of the parasite. 

 It so happens that D stands for danger- 

 ous and the table has been so arranged 

 that dangerous mixtures are thus easily 

 recognized by associating the letter 

 which designates the class with the 

 word. 



Interpretation of the Table 



The point must be brought out and 

 strongly emphasized that it is not in- 

 tended to recommend any particular 

 mixture shown in the table in prefer- 

 ence to any other. That is not the pur- 

 pose of the table. For example, an A-1 

 mixture is not necessarily a better mix- 

 ture to use than an A mixture. The 

 comparison is not between the mixtures 

 themselves but is intended to be made 

 solely between the mixture and the 

 original ingredients of the mixture; the 

 classification is intended to show the 

 effect of mixing only. It is seen by 

 looking at the table that a parts green- 

 bordeaux combination is classed as A-1 

 and a neutral lead arsenate-bordeaux 

 combination is classed as A. This 

 classification is not intended to mean 

 that the first combination is safer to 

 use than the latter, but that the parts 

 green-bordeaux combination is safer to 

 use than parts green alone and that 

 neither benefit nor harm results from 

 the mixing of neutral lead arsenate and 

 bordeaux. 



Arsenical-Fungicide Combinations 



Bordeaux. — Again referring to the 

 table, it is seen that both parts green 

 and acid lead arsenate are improved 

 by mixing with bordeaux. This is on 

 account of the excess of lime in the 

 bordeaux as now commonly used. The 

 lime forms a fairly insoluble compound 

 with the soluble arsenic in parts green 

 and acts in the same capacity after 

 spraying if any soluble arsenic is 

 formed by the action of the weather 

 upon paris green or acid lead arsenate. 

 Calcium arsenite cannot be improved in 

 this way, as this arsenical is made with 

 an excess of lime and the additional 

 lime of the bordeaux could not make it 

 more safe to use. No safer arsenical is 

 known than neutral lead arsenate; 

 therefore no added safety would result 

 by admixture with bordeaux. Insuffi- 

 cient data is at hand to warrant the 

 classification of the zinc aisenitc-bor- 

 heaux combination. 



Lime-Sulphur. — Lime-sulphur is now 

 coming to be a very formidable rival 

 to bordeaux mixture and the other cop- 

 per fungicides, and is also extensively 

 used as a contact insecticide. Hence it 

 is often desirable to mix this valuable 

 remedy with an arsenical. For this 

 purpose the choice of arsenicals is lim- 

 ited to lead arsenate, and very likely 

 should be entirely restricted to the 



neutral type. Lime-sulphur is a very 

 unstable compound and is easily de- 

 composed by slight influences, and is 

 especially susceptible to change when 

 mixed with other spray materials. This 

 fact is evident when it is noticed that 

 only two of its combinations are in 

 class A. Its own decomposition prod- 

 ucts are quite harmless, but its effect on 

 its associates is very frequently of a 

 serious nature. Particularly is this 

 true of its effect upon the arsenites 

 (paris green, calcium arsenite and zinc 

 arsenite). The arsenites in general are 

 less stable compounds than the ar- 

 senates and are prone to yield soluble 

 arsenic in either alkaline or acidic solu- 

 tions. The acid lead arsenate is also 

 unstable in alkaline solutions. Lime- 

 sulphur is of an alkaline nature, and 

 therefore the various arsenical-lime- 

 sulphur mixtures must all be placed in 

 the dangerous class, with the exception 

 of the neutral lead arsenate, and pos- 

 sibly with the exception of the acid 

 lead arsenate under certain favorable 

 conditions. Instances are known in 

 which acid lead arsenate and even 

 paris green have been sprayed in com- 

 bination with lime-sulphur without ap- 

 parent injury to foliage, but it is 

 thought that cases of this kind are very 

 rare and must have been done under 

 unusually favorable climatic conditions. 

 The acid lead arsenate-lime-sulphur 

 combination is given a question mark 

 in the table for the reason that many of 

 the reports of experiments make no 

 mention of the type of lead arsenate 

 used. Where the distinction is made, 

 however, the neutral type is favored. 



Iron Sulfid. — The so-called iron-sulfld 

 fungicide is prepared by mixing a solu- 

 tion of iron sulphate with an excess of 

 lime-sulphur solution. There results a 

 mixed i)recipitate of insoluble iron 

 sulfid (black), free sulphur (yellow- 

 ish) and calcium sulphate (white). 

 The excess of lime-sulphur is washed 

 out and there is left a paste of the three 

 precipitates which are quite insoluble 

 and inert toward most ordinary re- 

 agents. The iron sulfid is black and 

 is present in sulticient quantity to mask 

 the presence of the other precipitates. 

 The free sulphur is believed to be the 

 only constituent of fungicidal value, 

 the others being merely incidental to 

 this economical manner of precipi- 

 tating free sulphur in a finely divided 

 form. The iron sulfid and calcium 

 sulphate also serve to prevent the min- 

 ute particles of sulphur from floccu- 

 lating (i. e., uniting to form coarser 

 grains). From the above description, 

 the iron sulfid being composed of fairly 

 insoluble and inert substances, it may 

 be inferred that this material may be 

 mixed with any of the arsenicals with- 

 out fear of materially affecting their 

 composition. In some cases the lia- 

 bility of arsenical foliage injury is re- 

 ported to be lessened by the presence 

 of the fungicide in question. 



Other Free Sulphur-Paste Prepara- 

 tions. — Recently there have come into 

 the market other forms of finely di- 

 vided free sulphur mixed with defloc- 

 culating agents, notably "atomic sul- 



phur" and "milled sulphur." These two 

 preparations are composed of free sul- 

 phur ground to an impalpable powder 

 in the presence of a small quantity of 

 some material to prevent the floccu- 

 lation of the particles and enough 

 water to form a jKiste. Sulphur in its 

 elementary form (free sulphur) is in- 

 soluble in most liquids except the 

 alkalies and is indifferent to the influ- 

 ence of most of the substances present 

 in the various sprays. The defloccu- 

 lating agents are in small quantity and 

 are believed to have no detrimental 

 affect. Being of so recent origin and 

 of the nature of proprietary prepara- 

 tions, these are not included in the 

 table. So far as shown in printed re- 

 ports and from personal observation, 

 it is thought that "atomic sulphur" and 

 "milled sulphur" may be used with 

 safety in combination with the differ- 

 ent arsenicals. 



Potassium and Sodium Sulfids (Liver 

 of Sulphur, Sulphide of Potash, Soda, 

 etc). — Solutions or fusions of sulphur, 

 in soda or potash lyes, have long been 

 known as efficient fungicides and have 

 been more or less used as dormant 

 sprays. Their causticity has prevented 

 their very wide application as a foliage 

 spray and few attempts are reported to 

 combine materials of this nature with 

 the arsenicals. As noted in the reports 

 that are at haml, however, the results 

 of such combinations have been dis- 

 astrous, as might be expected, consider- 

 ing the susceptibility of most arsenicals 

 to the influence of alkalies. Interest in 

 fungicides of this class has recently 

 been somewhat revived through the in- 

 troduction into the state of a projjrie- 

 tary preiiaration known as "Soluble 

 .Sulphur," ofl'ered as a substitute for 

 lime-sulphur. This preparation is very 

 similar in composition to liver of sul- 

 phur, the chief difference being that the 

 former is combined with a sodium base, 

 while the latter is combined with a 

 potassium base. From a consideration 

 of the nature of the materials in (pies- 

 tion (potassium and sodium sulfids, 

 variously known as livei' of sulphur or 

 sulphide of potash anil sulphide of 

 soda, and "soluble sulphur") a combi- 

 nation spray composed of any of these 

 sulfids and any arsenical except the 

 neutral lead arsenate would be very 

 injurious when applied to foliage. It is 

 thought that the only possible arsenical 

 to use with these alkali sulfids is the 

 neutral lead arsenate, and even this 

 oi)inion is not given with absolute cer- 

 tainty in the absence of definite data. 



Arsenical-Contact Insecticide 

 Combinations 



Tobacco. — So far as known the vari- 

 ous forms of tobacco preparations are 

 compatible with the arsenicals, ])aris 

 green being a possible exception. (See 

 Tobacco-Bordeaux.) 



Soaps. — As previously noted in the 

 discussion of arsenicals-limc-sulpliur, 

 llie aisenites and the acid lead arsenate 

 are all unstable in the presence of al- 

 kalies. The alkalies of soaps, there- 

 fore, i)i-ohibit tlicir use with the ar- 

 Contimied cm \va'^c 35 



