12 



FARMERS BULLETIN 890. 



rollers. AVlien the lubber grasshoppers appear, control measures 

 must be taken immediately, because these insects can destroy a 

 plant very quickly. 



COTTON RED SPIDER.i 



One of the most destructive enemies of cotton is the red spider 

 (figs. 12-15), which is not an insect, but a mite. These mites can 



hardly be seen on the 

 cotton leaf, except 

 by a trained eye or 

 with the aid of a 

 magnifier, unless 

 very numerous, 

 when their minute 

 moving red bodies 

 make them distin- 

 guishable. They 

 multiply so rapidly 

 that they may 

 spread from a single 

 infested weed over 

 an entire cotton field 

 during the season. 

 The}^ suck the juices 

 and cause the leaf to 

 turn red and finally 

 kill the plant. They 

 usually work on the 

 underside of the leaf. 

 As the red spider is dependent on other idants tt) carry itthrough the 

 winter, it is apparent that weed control is a very important element 

 in reducing damage by this pest. Special bulletins are available for 

 those desiring complete information." 



The destruction of weeds, especially the 

 ])okeweed, and of cultivated plants such as the 

 violet, from which the mites make their way 

 to the cotton, and the destruction by plow- 

 ing up and burning of early infested cotton 

 ])lants are effective measures, which should 

 l)e used as primary means of control. 



When a cotton field is threatened by the red s])i(K'r it is often 

 advisable to spray. The following sprays are effective : (1 ) Potassium 

 sidphid (1 ounce to 2 gallons of water); (2) lime-sulphur solution 



Fig. 9.— Differential grasshopper: Above, adult male; below, adult fe 

 male. Twice natural size. (AValton.) 



(.;. 10.— Egg mas.s of differential 

 grasshopper. Enlarged. (San- 

 derson . ) 



1 Tetranychus telarius L. 



2 Department Bulletin 416, "The Red Spider ou Cotton."' and Farmers' Bulletin 831, 

 on Cotton and How to Control it." 



'The Red Spider 



