- 7 - 



Notes on Plum Curculio and Apple Maggot 



The season of 1938 was most unusual in its relation to the activity of 



the plum curculio. For three weeks after the first beetles were collected on 

 May 9 the maximum temperature exceeded 75° only on May 24. High temperatures 

 v/hich stimulated curculio activity did not occur until June 5 to 12, and even 

 then the period was interrupted by two days in the 60 's with generally cool nights. 

 This critical period of curculio activity which normally occurs about 10 days after 

 the calyx spray is applied was about three v/eeks later in 1938 » Although the 

 beetles were slow in appearing, the total number collected exc-eded that in 1^-37 

 and 1936. Due to the delayed activity of the curculio, nearly all trees were 

 sprayed before they were attacked and in spite of the abundance of beetles the 

 damage to apples is generally less than usual. 



The first apple maggot fly emerged in cagus at VValtham June 22. In 1934 

 the first fly w&s also found on Juno 22. The average date is June 28. This in- 

 dicates that the flies vifill be present early in July and sprays for their con- 

 trol should be applied at the recommended dates. It is not believed that the 

 maggot v;ill bo abundant this season but it seems to be a year of surprises and 

 anything can happen. (W. D. liVhitcomb) 



\ 



/'X 



/ 



Curculio beetle emergence 



A /' 



\ 



Maximum temperature - / \ '* ^' ^ ^ 





I 



. A- 



/ ; 



/ 





/ ^\ / ' 







\ 

 \ 

 \ 



\ 

 \ 



/ 



\- _ ' May Jy'}^ 



10 20 30 10 20 



