ECONOMIC ZOOLOGY ENTOMOLOGY. 



757 



pi. 1, figs. 3; ahs. in Jour. Econ. Eiit., 3 {1910), 'So. 2, pp. 2,73-255 ) .—The en- 

 courasing results obtained from cage experiments with powdered arsenate of 

 lead during tlie spring of 190S as previously noted (E. S. R., 20, p. 1150), led 

 the authors to inaugurate field tests. Small fields of cotton in a number of 

 localities were treated with the poison during the early summer of 1908, but 

 most of these were destroyed by overflows, etc. One series of experiments at 

 Mansfield, however, was carried out and is here reported. 



On May 28, powdered arsenate of lead was applied to approximately one-half 

 of a 0-acre field by means of a Champion dust sprayer, 1 lb. per acre being 

 used and pains being taken to force the powder well into the buds and terminal 

 leaves. Careful counts, made on July G, of infested squares and bolls in the 

 I)()isoned and nonpoisonod plats did not indicate any pronounced advantage in 

 the poisoned plat, but when the cotton was picked 5,008 lbs. was taken from the 

 poisoned plat of 4.83 acres, against 4,082 lbs. from the uonpoisoned plat of 

 4.712 acres. 



In experiments with a liquid spray of lead arsenate the gain was found to 

 be too small to justify the expense. In order to determine whether any con- 

 siderable number of weevils could l)e killed when squares and bulls were present 

 on the plants, cage experiments with powdered arsenate were made during July 

 and August in a field near Alexandria. The percentage of weevils killed by the 

 arsenate on fruiting cotton was considerably smaller than the percentage killed 

 on small cotton in the budding stage, but the outcome of these experiments 

 indicated that something might be accomplished by continuing the applications 

 of powdered arsenate for a time after the first s(piares appear on the plants in 

 spring. These results led to exi)eriments during 100!), 8 at Lakeland, Pointe 

 Coupee Parish, 1 at Woodside, Avoyelles Parish. 2 at Shaw. Cimcordia Parish, 

 and 1 at Mansfield, I)e Soto Parish. All of the field experiments were located 

 in localities where conditions were thought to be most favorable to the weevils, 

 in order that the poison could be given the severest possible test. The various 

 experiments are described in detail ; powdered arsenate of lead was used in all, 

 being applied by means of the Champion dust gun. The results have been 

 summarized in the following table : 



Hummanj of field experiments ivith powdered arsenate of lead. 



Experiment. 



Mansfield, 1908... 

 Lakeland A, 1909. 

 Lakeland B, 1909. 

 Lakeland C, 1909. 

 Lakeland D, 1909 

 Lakeland E, 1909. 

 Lakeland F, 1909. 

 Lakeland G, 1909. 

 Lakeland H, 1909. 

 Woodside, 1909... 



Shaw A, 1909 



Shaw B, 1909 



Mansfield, 1909. . . 



Number of 



applica- 

 tions pow- 

 dered 

 arsenate. 



Total 



amount of 



arsenate 



used per 



acre. 



Pounds. 



1.0 



2.2 



4.7 



7.0 



10.6 



14.5 



23.3 



51.0 



50.8 



44.0 



48.0 



26.5 



17.0 



Cost of 

 poisoning 

 per acre. 



SO. 42 



.04 



1. .33 



2.02 



2.90 



3.99 



6.16 



12.99 



12.94 



n.41 



12.39 



6.88 



4.54 



Yield of seed cotton 

 per acre. 



Poisoned 

 cotton plat. 



Pounds. 



1,049.0 



240. 3 



485.7 



208.7 



672.7 



342.9 



281.7 



392.0 



198.0 



533.7 



692.7 



1,167.5 



1,255.3 



Check plat 



Pounds. 

 993.0 

 82.1 

 180.3 

 101.6 

 127.9 

 103.1 

 79.8 

 76.0 



130.2 

 342.5 

 567.2 

 807.1 



Net profit 

 per acre. 



82.00 

 7.34 



13.55 

 .27 



23.54 

 7.69 

 3.63 

 2.35 

 7.07 

 8.16 

 4.68 



22.32 



17.22 



In practically every instance where the powdered arsenate was applied with 

 a Champion dust gun in the right manner, the right amount, and at the right 

 time, the outcome was profitable. As is shown in the above table, the highest 



