THE CODLING MOTH IN" THE YAKIMA VALLEY. 



37 





Fig. 22.— Seasonal history of the codling moth at Yakima, Wash., 1920. 

 SEASONAL HISTORY STUDIES OF 1921. 



The life-history studies of the codling moth were continued in 

 1921 in much the same manner as in the two previous seasons, and 

 considerably more material was handled, especially in the studies 

 of the spring brood. Complete data on wintering larvse were obtained 

 for the first time. No third-brood larvae were hatched in the in- 

 sectary. 



The development of the codling moth corresponded closely to 

 that of 1919. Minimum temperatures of 26° and 29° F. on April 

 24 and 30, respectively, delayed the blooming period of apples so 

 as to extend it over the period from April 26 to May 7. These 

 abnormally low temperatures froze many blossoms, but did not 

 cause a noticeable loss in the apple production of the valley. How- 

 ever, pupal development of the spring brood was interrupted, and 

 two periods of pupation resulted. High temperatures during the 

 time from May 30 to June 6 greatly hastened the development of 

 the codling moth, and many orchardists were late in applying the 

 first cover spray. The remainder of the growing season was favor- 

 able and the precipitation was only slightly below normal. 



