IHE RED SPIDER ON COTTON. 



59 



reaching the tip of the branch or leaf they fairly overrun one another 

 and become ensnared in the web spun by the later arrivals. In the 

 case of the perennial pea {Lathyrus latifolius) , the swarming con- 

 tmued until fully half of the area of the terminal leaflets was envel- 

 oped. A typical terminal leaflet was carefully exanuned and meas- 

 ured. The swarm was fomid to be built out to a thickness of 0.25 

 inch beyond the surface of the leaf, and all mites within the mass were 

 dead. One such swarm was found to contain about 15,000 mites. 

 Innumerable thousands of red spiders are eliminated in this manner. 





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Fig. 21.— Ideal outfit for spraying cotton fields: Barrel pump with douhle lead of hose mounted on 

 dismantled hayrake. (Original.) 



REMEDIAL MEASURES. 



PREVENTIVE. 



TituS; in 1905, was the first investigator to advocate the appHca- 

 tion of cultural methods as a means of controlling the red spider. He 

 suggested the rotation of crops, elimination of all plant, weed, and 

 grass growth near fields during the winter and early spring, and fall 

 or ^vint€r plowing to turn under aU vegetation. Worsham (1910) 

 also strongly recommended the destruction of all winter food plants 

 in proximity to infested cotton fields. 



W<; have already shown that red spiders readily establish them- 

 selve>^ on several of the native and dooryard plants. These hosts 

 serve as sources of dispersion. By destroying, during the winter and 

 early spring, pokeweed, Jerusalem oak, Jamestown weed, wUd black- 

 berry', wild geranium, and oth<'r plants which br<Hid the pest, much 

 good will be done. This plan has be(!n tested by the writer in sev- 

 eral instances and has given complet(^ immunity the following season. 

 Ewing nOH) states that this irh^a was tried in hop fields in Oregon, 

 with fh<'. result that the part of lh<i fn^ld that was W(^ll cleared of for- 



