THE MEXICAN COTTON -BOLL WEEVIL. 



147 



REPRESSION. 



EFFECT OF BURIAL OF SQUARES AND WEEVILS. 



The effect of the burial of squares and weevils is of considerable 

 importance for the reason that some degree of burial can be practiced 

 in the ordinary processes of cultivation. If it were to be found 

 that the weevils could be killed by a depth of burial which could be 

 accomplished without interference with the root system of the 

 plants this process would be of vast importance. 



At Tallulah, La., in 1910, Mr. G. D. Smith conducted an exten- 

 sive series of burial experiments. The infested squares were placed 

 in screened cages in the field. In each of these cages 2,000 infested 

 squares were placed on October 10. A careful estimate showed 

 that there were 250 live weevil stages for each 2,000 squares. In 

 the first of the cages the infested squares were placed upon a sheet 

 of wire screen 2 feet above the ground. These squares were kept 

 constantly moist. In the second cage the squares were placed on 

 the surface of the ground. No artificial moisture was supplied. 

 In the third cage the squares were on the surface of the ground but 

 were kept moist constantly. In the fourth cage the squares were 

 buried to a depth of 2 inches and the ground was kept moist. In 

 the fifth cage the squares were buried 4 inches and the ground was 

 kept dry. The artificial moisture was applied three times each day 

 during the course of the experiment. The "dry" cages were cov- 

 ered with canvas so that rains could not reach the squares. The 

 soil in the locality was the typical "buckshot" of the Mississippi 

 Delta. Immediately before the institution of the experiments 

 several rains had made the soil moist. Observations on emergence 

 were made from October 10 until November 15. 



Table LXVII summarizes the results of these experiments. 



Table LXVII. — Summary of experiments in the burial of squares infested by the boll 

 weevil at Tallulah, La., October and November, 1910. 



Cage 1 . . . 

 Cage 2... 

 Cage 3 . . 

 Cage 4 . . 

 Cage 5.. 

 Cage 6.. 

 Cage 7 . . 



Conditions. 



2 feet above surface, moist 



On surface, dry 



On surface, moist 



Buried 2 inches, dry 



Buried 2 inches, moist 



Buried 4 inches, dry 



Buried 4 inches, moist . . . 



Emergence 

 (weevils). 



119 

 157 

 147 

 62 

 6 



18 

 



Emergence. 



Per cent. 



47.6 



62.8 



58.8 



24.8 



.2 



.7 



.0 



It will be noticed that the greatest emergence was from the two 

 cages in which the squares were placed upon the surface of the ground. 

 At 2 and 4 inches beneath the surface the emergence was very small. 

 When kept dry beneath 2 inches of the soil 24 per cent of the possible 

 emergence occurred, but at this depth when moisture was provided 

 less than 1 per cent emerged. At a depth of 4 inches 0.7 per cent 

 emerged in the dry cage, but none from the same depth where mois- 

 ture was provided. It may be concluded from these experiments 

 that burial beneath 2 or more inches of dry soil of the " buckshot" 

 variety will prevent the emergence of a large portion of the weevils. 

 If the soil is kept moist with burial at 2 inches or more below the 

 surface the emergence is practically negligible. This is shown most 

 clearly by comparing cages 4 and 5 in the table. 



