172 REPOKT 



The practical application of such minute quantities in the open field is 

 out of the question, and so is the use of the undiluted powder on a large 

 scale, so long as its price is much higher than that of common flour. 

 Mr. Hubbard continUfes: 



Experiments in the fields witli the dry powder sifted upon the plants gave very 

 unsatisfactory results unless large quantities of the powder were used. On August 28, 

 a very windy day, I tried an application with the bellows, allowing the wind to carry 

 the powder in fine clouds iihrough the foliage, and using about one pound to the acre. 

 In this waj^, owing partly to the impossibility of securing an equal distribution, 

 some worms were affected at a distance of ten or fifteen feet, while others, much 

 nearer, were not affected at all. I have reason to believe that very few worms were 

 killed outright at this trial. Some recovered in a few hours. A number of those 

 which showed signs of pain, but had been very lightly dusted, I confined in vivaria, 

 and all completed their transformations in the usual time. At the time the fore- 

 going experiment was made the leaves were quite wet with recent rain, and another 

 heavy shower occurred later in the day. 



Prof. J. P. Stelle carried out, during his stay at Calvert, Texas, simi- 

 lar experiments with the same amount of undiluted powder and with 

 the same unsatisfactory results. Fortunately it has been found that if 

 unadulterated and fresh (which cannot be said in many instances of 

 the powder sold at retail by our druggists) it may be considerably di- 

 luted with other pulverized material without losing its deadly effect, 

 the use of the powder thus becoming much cheaper. Of the materials* 

 which can be used as diluents, common flour seems to be the best, but 

 finely-sifted wood-ashes, sawdust from hard wood, &g. — in short, any 

 light and finely pulverized material which mixes well with the pyre- 

 thrum powder — will answer the purpose. 



It has also been found that if the mixture of Pyrethrum and flour is 

 applied immediately after preparation it is always weaker in effect than 

 when left in a perfectly tight vessel for at least twenty-four hours be- 

 fore use. In the experiments made in 1879 we found that a mixture of 

 one part of Pyrethrum with ten parts of flour, applied immediately after 

 preparing, is sufficient to kill the average-sized worms with which it 

 comes in contact ; and that the mixture of one part of the powder to 

 sixteen parts of flour is equally efficient after being kept for some days 

 in a tight glass jar. The experiments made subsequently do not alter 

 these results to any considerable extent. It would be qiute superfluous 

 to mention here the experiments made with very strong mixtures of 

 Pyrethrum and flour, since they add nothing new to our experience, and 

 we shall refer rather to those which were made to ascertain the minimum 

 quantity of the powder necessary. The following series of experiments 

 was made at Selma, Ala., by Mr. Schwarz : 



Experiment 1, August 27. — Pyrethrum powder, one part, mixed with twenty parts 

 of flour, applied with the sieve immediately after preparing. Worms mostly more 

 than half-grown. Only a small proportion of the worms came in contact with the 

 mixture, though it was applied toward evening. These worms were affected within 

 the usual time, but upon examination, about ten hours afterwards, much more than 

 half the number had recovered. The mixture in this proportion, and applied with 

 the sieve, is evidently a failure. 



