August, '14] MCGREGOR: RED SPIDER CONTROL 335 



100 to 0. The large majority of the compositions proved to be en- 

 tirely ineffective against the red spider. A few proved to be deadly 

 to the mites but were eliminated owing to the fact that they were 

 injurious to the foliage. About eight sprays in all have weathered 

 this process of elimination and can be recommended with confidence 

 as efficient acaricides. These effective sprays are: (1) Potassium sul- 

 phid (3 lbs. to 100 gals.), (2) home-made lime-sulphur solution, (3) 

 kerosene emulsion, (4) resin-wash, (5 and 6) miscible oil (uncombined 

 and combined with "Black Leaf" tobacco extract), (7) "Sulfocide, " 

 and (8) flour-paste solution (diluted 1 to 8). From a rather extended 

 use of these compositions it seems established that if one of these were 

 to be used in preference to all others, it would probably be potassium 

 sulphid. This insecticide commends itself from every standpoint — 

 cheapness, simplicity of preparation, ability to kill quickly, and safety 

 of foliage. Altogether it seems to be an ideal red-spider spray. It 

 was found that 100 gallons, when applied as a misty spray, about 

 sufficed to treat an acre of average-sized cotton at a cost of about 75 

 cents for the material. 



Spraying outfits. — The sort of outfit to be used for red-spider spray- 

 ing depends mainly upon the extent of the occurrence. Some have 

 sprayed their score or so of affected plants with a 75-cent tin atomizer. 

 While this instrument is very economical of liquid and throws a misty 

 spray which penetrates and blows to all parts, it is not economical of 

 time. The bucket pump and knapsack pump come into use in cases 

 of considerable scattered infestation or for the treatment of a iew high 

 plants. The most economic outfit for a severe case involving several 

 acres consists of a barrel pump carried through the field on a wagon. 

 One man drives, one pumps, and one handles each sprayer (of which 

 preferably there should be two). Thorough treatment of three or 

 four acres per day is readily obtainable with this device. For safe 

 work, however, this outfit should be used only on cotton of average or 

 loAV size, as the passing wagon will injure large plants. 



Necessity for thorough spraying. — Some dissatisfaction has been 

 experienced among certain of those who have undertaken to check the 

 ravages of the red spider by spraying. This can be understood on 

 account of the extreme care which must be exercised in order to secure 

 effective results. In the case of insects which devour the plant tissue, 

 even the careless application of Paris green or lead arsenate to the top 

 of the foliage is often effective. This is explained by the fact that 

 such pests are constantly moving from leaf to leaf and will eventually 

 eat some of the poisoned tissue. Moreover, these insects often eat 

 entirely through the leaf, and hence it matters httle whether the poison 

 falls upon one side or the other. With the red spider, however, it is 



