334 JOURNAL OF ECONOMIC ENTOMOLOGY [Vol. 7 



Effects of fertilizers. — A rather elaborate series of tests with fertilizers 

 has been conducted in an attempt to determine whether the various 

 apphcations assisted cotton to withstand the injurious effects of infesta- 

 tion. The result of these experiments have been negative and it has 

 been impossible to deduce any definite conclusions. 



Repression 



We have just discussed cultural measures which may help to prevent 

 infestation. We will now consider what may be done to combat the 

 pest when it has already gained entrance to a field. 



As before intimated, we beheve in the efficacy of prevention rather 

 than cure, in the case of the red spider. When once well established 

 in a cotton field the pest is a difficult one to wipe out. That it is 

 possible, however, to eradicate the pest from infested fields has been 

 demonstrated beyond doubt, but in many cases the task is so tedious 

 that only the most determined farmers will undergo the effort neces- 

 sary to accom^plish the extermination. 



Removal of infested plants. — The experiment has been thoroughly 

 tested of pulling up and destroying the first few plants which show 

 infestation. In such cases the operation must be repeated several 

 times. Great care should be observed in locating every plant which 

 shows the characteristic red spots, and these must be carefully taken 

 from the field and burned. If infestation has not advanced far, this 

 treatment is usually effective, and a red spider invasion often may be 

 thus "nipped in the bud" and entirely eradicated. 



Occasional observation of instances wherein infestation had abruptly 

 stopped at a much-traveled road suggested the idea of plowing a wide 

 swath just outside the l^oundary of infestation. This was attempted 

 in one case where the infestation had covered about two acres. A. 10- 

 foot ring was plowed around the spot, and all stalks, both in the swath 

 and in the inclosed area, were immediately burned. Unfortunately 

 the farmer did not make sure that he was beyond the outermost zone 

 of infestation, and, consequently, a sufl&cient number of affected plants 

 remained outside the pulverized barrier to continue, somewhat, the 

 dispersion of the pest. This idea should be given further tests, as it 

 seems there should be great efficacy in the operation, provided the 

 swath is kept stirred frequently. 



Insecticides. — In the course of the investigations on the cotton mite, 

 almost two score of spray combinations have been thoroughly tested 

 under conditions entirely natural. Since no substance was discovered 

 which could be safely used to destroy all eggs in one application, it 

 has been found necessary to spray twice, with an interval of six or 

 seven days, so as to destroy the hatching larvse. The killing ability 

 of all these sprays was computed, and the percentages ranged from 



