150 THE MEXICAN COTTON-BOLL WEEVIL. 



owing to the peculiar habits and life history of the weevil, the poison 

 can in>t be so applied as to reach the immature stages at all, and it can 

 not reach the adults so as to cause sufficient mortality to result in any 

 considerable benefit to the crop. Much work has been done in thor- 

 oughly testing the effect of Paris green. The most important results 

 of this work have already been published in Farmers' Bulletin No. 211 

 of the Department of Agriculture. They will be described briefly on a 

 subsequent page. 



Among 40 other compounds tested, none proved worthy of even 

 passing consideration for field use. As a fumigant for seed, among 

 the eight gases or vapors tested, carbon bisulphid was found to 

 possess considerable value when applied in the special manner 

 described on pages 162, 163. 



POWDERED ARSENATE OF LEAD. 



In 1909 Messrs. YVilmon Newell and G. D. Smith, then of the 

 Louisiana Crop Pest Commission, published the results of certain 

 work with powdered arsenate of lead as a remedy against the boll 

 weevil. This work was done in central Louisiana during the season 

 of 1909. The principal experiments were located on three different 

 plantations on plats provided for the purpose. From 1 to 10 appli- 

 cations were made, consisting of a total amount of poison of from 1 to 

 51 pounds per acre. The treated cotton yielded an average of 71 per 

 cent more than similar cotton which was not treated. In all except 

 one of the plats there was a net profit from the use of the poison (that 

 is, after deducting the cost of the poison and of the labor from the 

 value of the increased yield) of from 27 cents to $23.54 per acre. In 

 the one exception there w T as a loss of $7.07 per acre. 



These striking results led to extensive work on powdered arsenate 

 of lead by the Bureau of Entomology. The services of Mr. G. D. 

 Smith, who was directly connected with the Louisiana work to which 

 reference has been made, were obtained. The bureau instituted 

 numerous experiments in Louisiana, including several which dupli- 

 cated the previous work in that State. This investigation has now 

 extended through two seasons in Louisiana, and considerable work 

 has also been done at Victoria, Tex., by Mr. J. D. Mitchell. 



In the experiments of 1910, 32 plats were utilized on plantations 

 at Livonia, Shaw, and St. Joseph, La., and Victoria, Tex. In the 

 work in Louisiana there w T as a profit from the use of the poison on 20 

 of the plats and a loss on the 12 remaining plats. The average loss 

 on the plats which failed to show a profit was $6.99 per acre. The 

 average profit on the remaining plats was $5.83 per acre. Twenty- 

 two of the 32 plats showed an increased yield of from 35 pounds to 403 

 pounds of seed cotton per acre. A striking result was the fact that 

 invariably the plats upon wlrich small amounts of the poison were 

 applied snowed profits. The work at Victoria, Tex., in 1910, con- 

 '1 of four experiments. In only one of these experiments was a 

 gain in yield obtained, and this amounted to only 59 pounds of seed 

 cotton per acre. In all of the experiments at this place there was a 

 1' >ss from the application of the poison of from $1.55 to $6.52 per acre. 



In L911 the work on powdered arsenate of lead was continued. In 

 some respects the results were contradictory of those obtained pre- 

 viously, but there w as agreement in that profits were obtained on all 



