1935 - Young, M. T. Boll weevil control with calcium arsenate on field plots in Madison 



Parish, Louisiana. U. S. D. A. Tech. B. 487, 24 p. 



An account is given of field tests to determine the effectiveness of calcium 

 arsenate dusts for the control of the cotton boll weevil. The tests took place from 

 1920 to 1934 in northeastern Louisiana, where conditions are favorable for the 

 insect. Calcium arsenate was generally used according to the standard method, 

 dusting being started when 10% of the squares were punctured and continued at 

 4 to 5 -day intervals so long as was necessary to keep the weevils under control, 

 particularly during fruiting period. Occasionally treatment was begun earlier and 

 continued longer. From 4 to 17 tests were made every year. Test plots and con- 

 trol plots were alongside one another. The area for picking, after the outer rows 

 had been rejected as a buffer, varied from about 0.2 to 0.5 acres. 



The average quantity of calcium arsenate applied per acre in one application 

 varied from 4.17 lbs. to 11.63 lbs. When it was necessary to start dusting early 

 in the season, more applications were required. Over the period of 15 years, the 

 average weekly infestation of cotton squares varied from about 10% in June, on 

 both treated and untreated plots, to about 47.5% on untreated and 22% on treated 

 plots in August. The average increase in yield per acre for the treated plots 

 ranged from 10 lbs. in 1924 to 742 lbs. in 1926, with an average of 356 lbs. or 

 30.2% over the complete period. In a few cases treated plots yielded less seed- 

 cotton than untreated ones. 



Tests made in 1920 showed that for early, intermediate, and late infesta- 

 tions the average increase in yield of treated over untreated plots was 43.9%, 

 34.5%, and 32.8%, respectively. With later infestations more cotton was produced 

 on both treated and untreated plots. 



Tests in 1927 on cotton planted at the usual time on unflooded land, and 

 planted late, after flood waters had receded from the fields, indicated that the 

 older cotton was first attacked and the young cotton became heavily infested only 

 when the weevils migrated. The average increase in yield of treated over un- 

 treated plots was greater on the cotton planted at the normal time. 



In 1928 the average infestation of squares on untreated plots was 5.0% to 

 22.1% less in fields planted with cotton for the first time than in those that had 

 also been planted with cotton in 1927. The percentage increase in yield of treated 

 over untreated plots was 36.1% in the first case and 45.7% in the second. 



In two special tests in 1932, dusting was begun much later, when migration 

 was in progress and the infestation of cotton squares was about 88%. Upon com- 

 pletion of 7 weeks of treatment, infestation was about the same on undusted plots 

 and 49% and 59% on the dusted ones. More calcium arsenate was used per acre as 

 the plants were larger. The increase in yield due to dusting was 75.7% and 319.3%. 



Dusting complete fields is more efficient than dusting separate plots, since 

 the weevils tend to migrate into the latter from untreated fields. The average 

 percentage increase in yield is closely correlated with the number of days that 

 have a precipitation of 0.3 inches or more, from the 21st of June to the 19th of 

 August, and to a lesser extent with the total precipitation during this period, and 

 the minimum temperature of the preceding winter. 



1936 - Strong, L. A. Report of the Chief of the Bureau of Entomology and Plant Quar- 



antine. U. S. D. A. 121 p. Wash. 



In cage tests of dusts against the cotton boll weevil, mixtures of calcium 

 arsenate with Paris green at the rates of 3:1 and 9:1 were more effective than 

 calcium arsenate alone; but in field tests, calcium arsenate alone gave better 

 results than these mixtures or than derris with sulphur (1% rotenone), Thio- 

 dipheylamine with sulphur (1:9), and calcium arsenate with lime (1:1). In a part 

 of South Carolina where infestation was not severe, the three best dusts tested in 

 order of profitable returns in control were: calcium arsenate with lime (1:2) 

 employed after the infestation had reached 10%; calcium arsenate with lime (1:1); 

 and calcium arsenate alone. Lime mixtures reduce the danger of soil poisoning 

 and heavy infestation with aphids. Experiments and experience over several years 

 indicate that the germination of the seed and survival of the seedlings of cotton, 

 maize, and soybeans are reduced in plots that have received heavy applications of 

 calcium arsenate against the weevil. 



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