20 THE RED SPIDER ON COTTON. 



In the course of npraying" tests against the red spicier on hops in 

 California, conducted by Mr. W. B. Parker/ of this bureau, it seems 

 to have been demonstrated that flour paste, used alone or combined 

 with caustic materials, is a valuable acaricide. The function of the 

 flour paste appears to be twofold : Used alone it glues the tiny mites 

 to the leaves, and when added to lime-sulphur, or other solutions, it 

 serves as a spreader to prevent the spray film from breaking up into 

 " beads " as it dries on the leaf. Mr. Parker recommends the follow- 

 ing formulas: 



I. Stock solution of flour paste. 



Mix cheap wheat flour witli cold water at the rate of 1 pound of flour 

 to 1 gallon of water. Boil to a paste. 

 II. Flour-paste spray. 



Use 8 gallons of the above stock-solution paste to each 100 gallons of 

 water. Keep constantly agitated while spraying. 

 III. Lime-sulphur and flour-paste mixture. 



Use 4 gallons of flour-paste stock solution to each 100 gallons of lime- 

 sulphur spray. 



During the recent season no serious effort was made to test addi- 

 tional insecticides. Further use of the sprays mentioned, however, 

 seems to establish the superiority of potassium sulphid, lime-sulphur 

 solution, and miscible-oil-tobacco solution. The last preparation 

 seems to possess better lasting qualities than the others, since, in the 

 absence of rain, one application will also suffice to kill a certain per- 

 centage of the hatching larvae. 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 mist spray, about sufficed to treat 

 an acre of average-sized cotton. 



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

 spraying 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 few 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 3 or 4 acres per day is readily obtainable with 

 this device. For safe work, however, this outfit should be used only 



1 Flour paste as a control for red spiders and as a spreader for contact insecticides, 

 Cir. 166, Bur. Ent., IT. S. Dept. Agr., January ^0, 1913; Tlie red spider on hops in the 

 Sacramento Valley of California, Bui. 117, Bur. Ent., U. S. Dept. Agr., 1913. 



