THE RED SPIDER ON COTTOISr, 



63 



field, to plow up all the affected portion in order to save the balance 

 of the field. The stalks should be piled up quickly and burned 

 with the assistance of straw or light trash. Such a severe measure, 

 however, should be resorted to only in extreme cases, and the planter 

 concerned must be the judge of its advisability. 



Since we have established by experimentation that red spiders are 

 unable to liberate themselves when buried 1 inch or more in soil, 

 the importance of plowing affected areas thoroughly is evident. 



INSECTICrDES. 



In the course of experiments with red-spider sprays 74 different 

 spray combinations have been tested. 



Table XXVII. — List of red-spider sprays employed with favorable results, Batesburg, 



S. C. 



1. Potassium sulphid. 



2. Kerosene emulsion. 



3. Lime sulphur (home-made). 



4. Lime sulphur (manufactured). 



5. A miscible oil. 



6. A water-soluble oil. 



7. Resin wash. 



8. Nicotine sulphate and miscible oil. 



9. Nicotine sulphate and fish-oil soap. 

 10. Fish-oil soap solution. 



In addition to these Successful sprays, special mention should be 

 made of potassium permanganate. In a 2 per cent solution this is 

 an excellent spray, but its cost is prohibitive, except in cases where 

 only a few plants are to be treated. 



Sulphur Preparations. 



Finely resublimed sulphur, both unadulterated and mixed with 

 dehydrated lime, was thoroughly tested on infested violets, dahlias, 

 roses, and cotton. It was applied with a dust gun during very warm 

 weather. Heavy infestation on prostrate violets was eradicated 

 by the sulphur dust; 60 per cent of the red spiders on dahlias were 

 killed; 25 per cent of those on roses were destroyed; and from 1 to 

 15 per cent mortality occurred on 4-foot cotton. Suspecting that 

 this variation in mortality came about through the agency of surface 

 radiation, th(; following test was made: A small area of ground sur- 

 face was thoroughly dusted with resublimed sulphur, and a heavily 

 infested potted violet plant was set into the center of this area, so 

 that no leaves touched the ground. The foliage, which had not 

 })een treated, was about 6 inches from the soil surface. Examina- 

 tion after 8 hours' (exposure im a vorj hot day showed that over 

 99 per cent of the mites had b(;en killed. When (elevated a distance 

 of 18 in(;he^s above the sulphured ground practically no mortality 

 occun'cd to infcsttnl violets. Tliis indicates that th(^ heat radiated 

 from th(! ground (acting on tlu; sulphur imm(uliately at hand) is the 

 chief factor whi(;h determines the mortality resulting from the use 



