152 REPORT 4, UNITED STATES ENTOMOLOGICAL COMMISSION. 



also in very dry weather, tlie proportion of J pound to 18 of the dilu- 

 ents is most to be recommended. This refers to very economical appli- 

 cation by means of a careful handling of the sieves. As the sifting is 

 generally done less economically, the following proportion is to be 

 recommended : One pound of the purple to about 45 pounds of diluents, 

 the hitter most advantageously consisting of 15 pounds of wood ashes 

 and 30 pounds of flour, including the usual amount of adhesive mate- 

 rials. This would give about 4 pounds of the purple to 1 barrel of flour. 

 As to the cost per acre of cotton, the remarks made under the head of 

 Paris green also hold true here, the low price of the purple rendering 

 its application of course so much cheaper. 



The expeiiments made by the agents of the Commission in applying 

 the purple without diluents have completely failed for want of machines 

 wherewith to apply evenly the very small quantity of the poison re- 

 quired for each plant, the results invariably being that the leaves were 

 considerably scorched. The invention of machines bringing about the 

 even distribution of very small quantities of poison will naturally open 

 a wide field for further experimentation. That even a very slight dust- 

 ing with the purple mixture mentioned above is fnlly efficient has been 

 proved by the experiments made in Texas in 1879; but such economic 

 application is impossible on a large scale, so long as we cannot dispense 

 with the sifting methods. 



Wet application. — Like Paris green, it is not soluble,* but is much 

 easier kept suspended in water than the former. If applied in this way 

 some care has to be taken in stirring it in the water, as it has a tendency 

 to form lumps, owing to its finely-powdered condition. Experiments 

 on a large scale with this material diluted in water gave the following 

 results : When used in the same proportion as Paris green, namely, 1 

 pound of the poison to about 40 gallons of water, one experimenter 

 reports that the leaves were slightly crisped, while four others report 

 perfect success, and no injury whatever to the plant. Experiments by 

 ourself and Mr. Schwarz in the year 1879 showed that when applied 

 in the proportion mentioned and thoroughly stirred up in the water the 

 leaves were partly crisped, though by no means so much as by arsenic, 

 even when applied in weaker solution. When used in smaller propor- 

 tion, or at the rate of f or J pound to 40 gallons of water, it did not burn 

 the leaves, and still proved efl'ectual in destroying the worms. Re- 

 peated experiments on a smaller scale confirmed these results obtained 

 on large fields, and also showed that the proportion may be still farther 

 reduced, and when applied with great care and in very dry weather J 

 pound to 40 gallons will kill. Still farther reduction in the proportion 

 of the powder used gave negative results. I would therefore recom- 

 mend the use of ^ pound of this powder to from 50 to 55 gallons of 

 water as the proportion most likely to give general satisfaction by 

 effectually destroying the worms without injuring the plants. 



* The manufacturers can render about 13 per cent, of it soluble if desired. 



