BUREAU OF ENTOMOLOGY. 519 



southern Texas and in the southern parishes of Louisiana. Consid- 

 erable damage was done also in Mississippi. A conservative estimate 

 of the loss will be about $15,000,000. 



On account of the obviously greater difficulty of the boll-weevil 

 problem in the Mississippi Delta than elsewhere, as pointed out in 

 previous reports, a well-equipped laboratory was started at Tallulah, 

 La., where conditions characteristic of the whole delta region exist, 

 and during the j^ear substantial progress was made in the study of 

 new means of control. Especial attention was paid to the possibility 

 of utilizing parasites of the boll weevil. On account of the scarcity 

 of material for breeding parasites in Texas it was impossible to carry 

 the work as far as was desired. Nevertheless some practical indi- 

 cations of success have been obtained. 



An important series of experiments was begun to determine the 

 proper spacing of cotton plants in the field in order to obtain the 

 maximum benefits of the factors in the natural control of the pest, 

 including the parasites. These plats were located at five points in 

 Louisiana. 



The chain cultivator, perfected by the Bureau, was tested wdth 

 especial reference to its adaptability to the peculiar soil conditions 

 of the delta, and a study was made of the possibility of flooding the 

 fields to kill the weevils in their hibernating quarters. This method 

 will probably be practicable in some localities. 



In connection with the utilization of the parasites of the weevil a 

 study was made of the relative abundance of the flow of nectar with 

 the different varieties of the cotton plant. This nectar furnishes the 

 only food, so far as known, of the adult parasites. Therefore the 

 cotton varieties that secrete the most nectar may be supposed to at- 

 tract the parasites which will destroy the weevils. Also the cotton 

 varieties which hold the squares best have been found to be more 

 heavily parasitized than other varieties of cotton plants. Therefore 

 a study of varieties having this habit has been carried on. 



Extensive experiments were made in the effort to obtain definite 

 knowledge regarding the hibernation of the weevil in the delta. The 

 results obtained from these experiments will indicate the best time 

 to take the greatest step in the control of the boll weevil, namely, 

 the destruction of the cotton stalks in the fall. 



Efforts were made also to ascertain the exact effects of excessive 

 moisture on the hibernating insects, since it has been suggested that 

 the heavy precipitation in the delta region may be unfavorable to 

 the weevil during the hibernation period. 



On account of the apparent success of experiments made by the 

 Louisiana state crop pest commission with powdered arsenate of lead, 

 experimental Avork in this direction has been carried on by the 

 Bureau. Arsenate of lead is a very finely divided powder, and will 

 reach parts of the plants that can not be reached by Paris green or 

 other compounds hitherto used. An effort was made to ascertain 

 how many applications are most profitable and the proper interval 

 between applications. The experience of practical planters in using 

 the poison has been collated. Work of this character was also begun 

 in Texas. An important objection against the use of arsenate of 

 lead is its high price, and, moreover, recent experiments seem to 

 indicate that its effect upon the soil under some conditions may be 

 very deleterious. The Texas experiments include a study of arsenical 



