57 



pyrethrum was made by simply digesting the powder iu kerosene for three or four hours. 

 The resulting emulsion is good, and it is about as effective on the Oabbage Worm as he 

 claimed it to be on the Cotton Worm. Mr. Gillette's mixture I made with the same 

 proportion of soap, kerosene and pyrethrum as the first mixture contained. * * * 

 The emulsion was made in the usual manner, and then it was diluted with the kerosene 

 tea. When Dr. Menke's mixture was diluted equally, there was no difference between 

 the two in appearance or odor. In using dilutions of the strength, fewer worms survived 

 the application of Mr. Gillette's solution, but the difference was immaterial, as when I 

 applied the mixture without knowing which I was using, I could not always tell which 

 of the two I had employed. Such in brief are the conclusions I have reached after a 

 considerable number of experiments with the two. I shall not be satisfied, however, 

 without further trial of these mixtures upon different worms. One thing that has dis- 

 turbed my satisfaction with these experiments is, that in many cases where [ had applied 

 a dilution of a given strength to larvge of different age, the younger larvfe seemed less 

 affected than the older. Concerning the difference between an aqueous extract of 

 pyrethrum made into an emulsion with kerosene and soap, and a kerosene extract of 

 pyrethrum made into an emulsion with soap and water, there is no practical difference. 

 It may be of some slight interest to scientific people to know that the aqueous extract 

 and the kerosene extract are technically different. As far as their use is concerned these 

 two are absolutely one. If there is any practical difference between them, the aqueous 

 extract emulsion is preferable. I have never made any public claim to having originated 

 the idea that kerosene would dissolve the insecticide principle of pyrethrum. What I 

 wanted to announce the discovery of was, that the two insecticides, kerosene and pyreth- 

 rum, could be combined in an emulsion which would be more effective than either. 

 When I was assured by Mr. Mally (an agent of the Division) that he had made such a 

 mixture while working with Mr. Gillette, my personal interest in the matter ceased. Dr. 

 Menke claims to have discovered an " entirely new " insecticide which is remarkable for 

 its cheapness. 1 think 1 have shown that it is composed of the same materials which 

 may be used in the same proportions, so that the difference between his emulsion and Mr. 

 Gillette's is in method of preparation, and in this respect his method is decidedly the 

 inferior. The chief difficulty in the use of pyrethrum in kerosene emulsion is the cost 

 when compared with the cost of the arsenites in the form of powder or in solution. 

 ****** 



Mr. Smith had tried the kerosene-pyrethrum combination according to Menke's 

 formula, but had found it of no use against the Rose Chafer. 



In response to a question by Mr. Smith, Mr. Alwood stated that he buys imported 

 powder for from 38 to 40 cents per pound at wholesale in New York For buhach he has 

 to pay 75 cents per pound and considers that one is as good as the other. He finds that 

 he can keep the powder in bulk for two or three years, with care. 



Mr. Webster stated that he could buy it by the 10 or 20 pounds in Lafayette, Ind., 

 at 30 cents per pound. 



Mr. Alwood stated that in his opinion this powder must be adulterated on account of 

 the cost of production in Dalmatia. 



Mr. Smith buys in Philadelphia for 25 cents per pound. 



Mr. Weed had found kerosene combined with pyrethrum perfectly useless against the 

 Harlequin Cabbage Bug. Kerosene emulsion is also ineffective against the same insect. 



Mr. Alwood, however, had found it effective for this insect. 



Mr. Weed stated that he had killed the plants but not the bugs. He has found the 

 eggs of this insect to hatch in three days in Mississippi (first brood), those of the second 

 brood hatching in two days, and those of the later brood in four days. These periods, how- 

 ever, are not definite, and considerable variation occurs. 



Mr. Smith finds this species in southern New Jersey, but never upon cabbages. 



Mr. Doran stated that the bugs can be caught upon Mustard before the cabbages are 

 set out. 



