756 EXPERIMENT STATION RECORD. [Vol.43 



" In their physical properties there is considerable variation. By improving 

 the physical properties of the spray solution we are enabled to improve the 

 efficiency of the spray: (a) By increasing the wetting and covering power of 

 the spray solution; (b) by increasing its adhesiveness. . . . The spray solu- 

 tion, without the addition of a spreader, as normally applied to the waxy sur- 

 face of an apple finally rests as an irregular, blotchy coating of uneven thick- 

 ness and with interspaces but poorly coated or free from spray. The spray 

 solution, with a spreader, applied tp the surface of the apple, finally rests as 

 a smooth, even, inconspicuous covering, affording practically an equal and per- 

 fect protection for every surface. Materials showing value as spreaders in the 

 poison spray solution, given in the order of their merit, based on compatibility, 

 efficiency, availability, cost and ease of preparation, are caseinate, glue, gelatin, 

 soap bark, and oil emulsion. In preliminary experiments conducted thus far 

 these spreaders are not improved by the addition of phosphates and sulphates. 

 Methods have been developed for testing the comparative wetting values of 

 spreaders for the surface of the apple fruit by means of capillary tubes. 



" The improvement of the physical condition of any one of the three factors, 

 method of application, the spray solution, and the spray material, decreases 

 the relative importance of defects in the other two. The physical properties 

 of the spray material and of the spray solution are inversely prpportional to 

 the power and agitator effectiveness of the outfit. Where the agitator is faulty 

 or mediocre, where the pressure capacity is limited, or the spray nozzle defec- 

 tive, the efficiency value of improved solution and materials rapidly increases 

 in importance. The importance of the capacity of the outfit and physical quali- 

 ties of the material are inversely proportional to the wetting, covering, and 

 adhesive properties of the spray solution. The importance of the physical solu- 

 tion and capacity of outfit is inversely proportional to the fineness, uniformity 

 of division, powers of suspension, and adhesiveness^f the spray material. 

 Where the physical qualities of all three are developed to the highest possible 

 standard we should, in the hands of a careful manipulator, approach the ideal 

 protective covering sought for in a spray application. A fine, misty spray applied 

 in the calyx application for codling-moth control is equal in effectiveness to a 

 driving spray. 



" The total calyx worms in the commercial orchard in Oregon is usually less 

 than 50 per cent of the total worm infestation. In commercial orchards in 

 Oregon where a spray program is practiced, the worm infestation is normally 

 light until late summer. Data accumulated for a series of years shows that 

 it is the late summer brood of moths, giving rise to the worms which infest 

 the fruit during late Ailgust and early September, causing the costly ' Septem- 

 ber sting,' that is responsible for our heavy losses from wormy fruit. To 

 attach undue importance to the calyx application has not been found warranted 

 in our experiments. All applications are essentially of equal merit, and con- 

 scientious effort in their application is desirable. The last summer applica- 

 tion is particularly significant because of the difficulty in timing it properly. 



" The calcium arsenates have a high killing efficiency as a poison spray for 

 chewing insects. They are not so stable as are the corresponding lead salts, 

 and for use in commercial orchard spraying, under western Oregon conditions, 

 it is advisable to have an excess of lime present in the solution. Methods of 

 manufacture have not been standardized, and commercial brands of calcium 

 arsenate vary greatly in their chemical and physical properties. There is at 

 present probably no adequate reason for a wholesale abandonment of the lead 

 in favor of the calcium arsenate for orchard work. 



" Nicotin sulphate is a powerful repellant for tent caterpillars. They will 

 not ordinarily feed from choice on foliage sprayed with It. Where feeding does 



