August, '14] McGREGOR: RED SPIDER CONTROL 333 



"Wilt Proof," Toole, Peterkin, Broadwell, and Cook suffer most (in 

 the order named) from the attack of the pest, while Hite, Russell, 

 Summerour "Half and Half," and Cleveland showed the greatest 

 immunity of all the varieties investigated. Further investigation of 

 this feature of the problem will doubtless throw additional light on 

 the relative desirability of the common cotton varieties from the 

 viewpoint of immunity. 



Spacing. — It has been claimed by one investigator, who held that 

 intrafield dispersion occurred only directly from l^ranch to branch, 

 that wide spacing of the stalks, by preventing the interlacing of the 

 branches, would prevent the spread of the red spider through a field. 

 Experiments at Batesburg have shown that the red spider commonly 

 travels between plants upon the ground. Thus, although dispersion 

 might be slightly impeded through the adoption of wide spacing, the 

 futility of this measure becomes evident in view of the regular occur- 

 rence of terrestrial travel. 



Time of planting. — There is yet much doubt as to the relative 

 advantages of early and late planting. Extremely early planting 

 naturally permits the plants to develop a maximum growth of weed 

 and fruit by the time of serious mite appearance. It is noticeable that 

 plants of considerable size are rarely killed by the pest, nor are well- 

 advanced bolls commonly shed from infestation. On the other hand, 

 several fields about Leesville, S. C, which were planted as late as June 

 20, seem to have largely escaped the infestation which was so general 

 at that locality. Late planting, however, is almost universally objec- 

 tionable to the farmer, since in ordinary seasons it results in a reduction 

 of the jdeld. 



Rotation.— In an effort to test the rotational value of other crops, 

 numerous field crops have been planted in or near infested areas. In 

 addition, frequent examinations have been made of a great many 

 garden and vegetable crops in infested localities. Besides cotton, 

 red spiders are known to occur not at all uncommonly upon the fol- 

 lowing field crops: Cowqoeas, clover, corn, hops, and watermelon. 

 They are also found frequently on the following garden crops: Peas, 

 beans, onion, tomato, lettuce, okra, turnip, mustard, squash, beet, 

 sweet potato, and strawberry. A really acute infestation on corn 

 was seen at the height of the 1912 season. Cowpeas are particularly 

 attractive to the pest, and sweet potatoes have been noted to be badly 

 infested. Should an immune crop be found and employed, it is ex- 

 tremely probable that the pest would reinvade the fields upon the 

 return to cotton culture with as great ease and quickness as it has 

 done during any previous season, providing the sources of infestation 

 were at hand. Rotation, then, does not promise to contril)ute toward 

 the solution of the problem. 



