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Patented May 10, 1938, 2,117,158 UNITED STATES PATENT OFFICE 2,117,158 ' ' METHOD OF EXTERMINATING-CORN > BEETLES AND OTHER VEBMIN ' Werner Freyberg and Walter Haupt, Delitzsch/ Sachsen, Germany, assignors to Ernst Freyberg Chemische ‘ Fabrlk Delltia, Delituch/Sachsen, Germany v No Drawing. Application October 16,1935, se; $314 No. 45,368. In .Germany November 6, .7 Claims. ‘(Cl- .. 99—225) This invention relates to the extermination of never gas-tight cannot be ?lled with large quanti corn beetles and other vermin.- . ties of' phosphine since, apart from the large The damage caused by the corn beetle to grain quantity of phosphine which would be necessary. stored in the granary is only too well-known to the danger associated with its use would exclude 5 the persons concerned. The annual value of the the practical employment of such a process. grain which is destroyed by com beetles is It has now been unexpectedly found that the estimated to amount to about 100,000,000 reichs development of phosphine in a concentration mark for Germany alone. In spite of the extreme which is fatal to corn beetles and other vermin importance of the problem of exterminating corn can-be successfully obtained by placing solid sub 10 beetles and like vermin, no one has yet suc stances which evolve phosphine in theimmediate 10 ceeded in discovering an absolutely reliable neighbourhood of the grain, that is between or means for eradicating these and other pests from close beside or cum in the heaps of grain which grain-and other seeds. Sprays must, of course, are attacked by the corn‘beetles. ‘ be excluded from the start for this purpose as'the ‘ As the, solid substances which develop phos-- V 15 grain stored in the granary would be much phine, all._possible phosphides, such as calcium 15 damaged if these were used. Gassing the phosphide, barium phosphide, aluminimn phosa granaries with poisonous gases appeared to offer phide, magnesium phosphide and so forth are ' the greatest prospects of success but the note- I suitable for being used. These substances when worthy fact was discovered that the corn beetle they are introduced in 'a suitable packing into has a relatively high power .of resistance even to the stored grain gradually give .03 phosphine in O hydrocyanic acid, so that even this extremely continuously increasing amount owing to the poisonous gas, theme of which moreover is‘ asso moisture contained in the grain. The evolution ciated with much inconvenience and danger, can~ of gas is still further promoted owing to the fact not be said to be absolutely certain in its action. ‘ that grain which has been attacked by com 25 Thus, forv example, it is stated in a lea?et of "the beetles generally contains a higher percentage of Biologische Reichsanstalt of Berlin-Dahlem is moisture and is also of a slightly higher tem sued in June 1934, that “Absolutely reliable and perature'than sound grain. It is particularly im thoroughly e?ective‘ gassing means for checking ' portant that the phosphine should'be evolved the corn beetle have not yet been found up to the. gradually when the new process is employed. 30 present time.” I . On the one hand, the danger of self-ignition It is therefore an‘ object of the present inven— which might be present if a large quantity of ‘ tion to provide new methods of exterminating phosphine were suddenly evolved is obviated with corn beetles and other vermin in grain. certainty. On the other hand, it is just this slow It is another object of the invention to pro- " action of a, gradually increasing concentration of 35 vide a method for eradicating corn beetles and poisonous gas which appears to effect the killing other harmful vermin, 'as- well as their‘larva'e, of the corn beetles with absolute certainty, where from stored grain and other seeds. as the sudden action of large quantities ofthe It is a further object of the present invention poisonous gas appears to put the vermin into a to provide methods of ‘developing phosphine in state in which they are insensitive ‘to further 40 granaries in concentrations su?lcient to kill corn quantities of the‘ gas, without, however, being 40 beetles and their larvae. ' completely killed. 7 ' It is also an object of the-invention to provide’ In order to prevent as far as possible the escape methods of [evolving phosphine from calcium of the poisonous gas into the neighbouring atmos phosphide and other similar phosphides without phere and to ensure a gradual increase of the I 45 danger of self-ignition. \ concentration of the gas in the heaps of grain It is ?nally an object of the present invention which are attacked by the vermin, it is advisable to provide a method for gassing stored grain to cover the grain with sacks, tarpaulins, paper without using gas tight chambers. or the like during the treatment. ' Other objects and advantages of the invention It has been found that with this treatment will appear from the following description. the corn beetles and other harmfulinsects, as so The poisonous action of phosphine on corn well as their'larvae, which may be contained in beetles and other vermin is in itself well known, the grain are killed, although, if the dosage of ' , Nevertheless, it has not previously been possible the compound which evolves the phosphine be in practice to use this gas in granaries and the correct, afterri to 8 days hardly any smell of like. Naturally, granaries which are practically phosphine can be noticed in the granary, so that 2 2,117,15e the granary can then be entered as usual without of phosphine which may still be adhering to the danger and the residue of the vermin exterminat grain. ing agent can then be removed from the grain. As has already been mentioned, the most var The dead corn beetles and other insects can be ied phosphides such as calcium phosphide, bar separated from the grain in known manner, for ium phosphide, aluminium phosphide, magnesium example by winnowing whereby the grain simul phosphide and the like can be employed. The taneously becomes aerated‘ and the last traces most practicableform in which to use the phos of any odour of phosphine which may adhere phide is, of course, in the form of powder. A vto it are eliminated. ( powder can not only be easily measured out with a - vIn order to introduce into the heap of grain measuring vessel, spoon or ?lling machine but 10 the compound which evolves phosphine, the com the properties of a substance are also most uni pound must be packed in a suitable gas-pervious form when it is in powder form. It has been packing. It has been found advantageous for found,- however, that the pulverulent phosphide this purpose to wrap the phosphide in a dry bag compounds of' calcium, magnesium and barium made of paper, fabric or metal gauze which itself . are not very stable. They give oil? hydrogen 15 is contained .in a case which is made of ‘sheet phosphide in the sheet metal boxes which are metal, arti?cial material, porcelain or the like employed for their carriage or transport and may and is perforated and is again inserted in a sec thereby burst open the boxes. It has also been ond bag made of gauze.’ This packing is pref found by experience that phosphides in the form 20 erably provided with a thread to which a coloured of lumps or pieces keep better, so that they can 20 tab is attached so as to enable the bag to be easily be placed on the market in tightly closed sheet found in the heap of grain after the gassing has metal containers. , been completed. _ g I Calcium phosphide in the form of lumps or -When used'in practice thenew process is ex pieces, however has the disadvantage that it can 25 tremely inexpensive. Thus, under. favourable only be measured out into the form of doses with 25 conditions, it has been‘ found by experience that di?iculty. Pulverization by the user in a mor it is su?icient to .use about 30 grammes -of cal tar or the like‘ before use is out of the question cium phosphidevto each cubic metre, i. e. about because the pieces of calcium phosphide are very 15 hundredweight, ofigrain. ‘Under less favour 'hard. A further undesirable property of cal 30 able conditions, for example, when thetempera cium phosphide is that thecontent of phosphide 30 ture is lower, several times the amount indicated in the individual pieces varies. may, however, be employed. In' order that When gasifying the phosphides of calcium, quantities of the material which always evolve magnesium and, barium in the form of lumps, it the same amount of poisonous gas may always has been found thatvthe products of decomposi 35 be available, it is advisable to employ the calcium tion formed during the gasi?cation occupy a con phosphide in the form of tablets of standard side. siderably greater volume in comparison with the The new process has the great advantage that, ' original \material and this increase in volume in contradistinction to 'all the gassing processes may amount to up‘to about 30%. Consequently hitherto known, it is not necessary to employ gas the sheet metal containers which, for- example, tight chambers,- yet the vermin including their may be employed for the gassing may in some 40 larvae are destroyed with-absolute certainty. At cases be burst open so that the poisonous mate the same time, it has unexpectedly been found rial may escape.

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