14 



BULLETIN" 712, IT. S. DEPARTMENT OF AGRICULTURE. 



Washington section of the Weather Bureau show the following con- 

 ditions prevailing at Wenatchee during the period when spray in- 

 jury occurred: 



Measurable precipitation. 

 April, none. 



May, 1.77 inches, distributed over May 1, 2, 9, 10, 11. 14, 17, 23, 24, 27. 

 June, 0.21 inch, distributed over June 10, 11, 12, 23. 

 July, 0.28 inch, distributed over July 4, 8, 14, 26, 27. 



Mean maximum and minimum temperatures. 



Month, 1915. 



Maxi- 

 mum. 



Mini- 

 mum. 



Month, 1915. 



Maxi- 

 mum. 



Mini- 

 mum. 



April 



°F. 



70.3 

 68.2 



°F. 

 42.2 

 46.0 



June 



°F. 

 80.1 

 86.4 



°F. 

 53.5 



May 



July 



57.9 









The maximum temperature was between 80° and 90° F. on April 16, 17, 18, and 

 19, on May 4, 6, 7, and 8, on June 3, 6. 7, 13. 14, 15, 20, and 21, on July 5, 7, 8, 

 17, 18, 26, 29, and 30; between 90° and 100° on June 4, 5, 22, 23. 29, and 30. 

 and on July 1, 4, 19, 20, 24, 25, and 31 ; and above 100° on July 2, 3, 21, and 23. 



The above temperatures are shade temperatures. The tempera- 

 tures on fruits exposed to the direct rays of the sun were naturally 

 much higher. Tests made to indicate what this difference might be 

 showed that the temperature was 20 to 30 degrees higher in the 

 sun. From this it appears that the sun temperature ranged well 

 above 100° F. on five successive days (June 3-7) just before the 

 appearance of the fruit burning. No other excessive temperatures 

 were recorded between the date of the last spraying and the appear- 

 ance of the injury. With the continuance of the hot weather the 

 injury was observed to increase to some extent, but most of the fruit 

 exposed to direct sunlight was injured at the start. There was no 

 indication that the scanty precipitation had any effect on spray in- 

 jury either to fruit or foliage. The foliage injury appeared to be 

 the result of toxic action of the wet sprays, probably intensified by 

 the bright sunlight, since it began to appear so shortly after the 

 application. 



It was a rather difficult matter to arrive at an accurate or repre- 

 sentative measure of the control established, especially in the case 

 of infected leaves and twigs, which constitute the principal mani- 

 festation of the disease. The variation in the crops of fruit was so 

 great among the different plats that no data could be secured on 

 fruit russeting ; hence the results had to be measured by the condition 

 of the vegetative parts. An empirical estimate of the degree of infec- 

 tion is largely influenced by the personal equation, and an inspection of 

 all the foliage and twigs was manifestly impossible in an experiment 

 of this magnitude. Actual counts were therefore made to show the 



