630 ANNUAL REPOBTS OP DEPARTMENT OF AGRICULTURE. 



spider and grow in the immediate vicinity of cotton fields were de- 

 stroyed by burning before the infestation of the cotton field had be- 

 gun. By this means the spider was destroyed and no infestation of 

 the cotton field occurred. Methods were also devised for use in cases 

 where it has not been possible to prevent the invasion of the fields. 

 In one experiment the first few cotton plants that became infested 

 were pulled out, carried from the field, and destroyed. In this way 

 a single field which had shown damage each season was kept clear. 

 In another experiment the plowing under of cotton planted broad- 

 CHSt rear the edge, which served to concentrate the spiders on their 

 migration from the original host plants to the cotton, checked the 

 invasion completely. It was also discovered that the use of a solution 

 of potassium sulphid in water is an economical and effective method 

 of destroying the spider when it has invaded a field. By this means 

 the agent engaged in this work prevented the spread of the red spider 

 by the application of a spray which cost only 75 cents per acre. 



The survey of several of the eastern cotton States to determine the 

 amount of damage caused by the red spider, to which reference has 

 been made, resulted in a determination of the fact that injury is 

 spread over a very wide territory. Throughout the States of North 

 Carolina, Georgia, Florida, Mississippi, and Alabama the spider was 

 found in the cotton fields. In many places in these States the injury 

 was as severe as in South Carolina. It has generally been overlooked 

 by planters or considered to be some sort of rust. 



BICE INSECTS. 



The work on rice insects was conducted at Crowley, La., where 

 excellent facilities were furnished by the Louisiana experiment sta- 

 tion. The main work on rice insects was with the so-called rice 

 water- weevil. In addition to the study of the life history of the pest, 

 considerable work was done in practical control by management of 

 the water. It was found that the weevil is checked to a very con- 

 siderable extent by such draining of the fields during the growing 

 season as is not sufficient to affect the rice materially. These observa- 

 tions have led to an extensive series of experiments to determine 

 exactly how the water used in flooding the fields may be manipulated 

 to check or greatly reduce the ravages of the weevil. 



Observations were made on a number of minor enemies of the nee 

 plant, some of which will eventually require careful consideration. 

 Up to the present time, however, it has been necessary to concentrate 

 the work on the principal species affecting the crop. 



MISCELLANEOUS. 



During the year an opportunity arose for testing various forms of 

 electricity, including Roentgen rays and high frequency currents, 

 for their possible utility in the destruction of injurious insects. The 

 work dealt largely with the determination of the possibility of steril- 

 izing insects by means of Roentgen rays, as it was to be assumed that 

 insects might be affected somewhat in the same manner as human 

 beings are known to be. A rather elaborate apparatus was placed at 

 the disposal of the bureau and tested at New Orleans. The results, 

 although extremely interesting from a scientific standpoint, did not 



