PLUM CURCULIO IN APPLES 



13 



from May 26 to June 1. ^'ery few curculios were in the trees before this time (Fig- 

 ure 3), and the dividing hne between eiTective and late control treatments was 

 May 28, as is indicated by the double line in Figure 5. 



Figure 5. — Relation of Maximum Daily Temperatures to the Activity of the 



Beetles During the Critical Period for Control of the Plum CurcuHo. 



Waltham, Mass., 1931 



?i 24 25 26 i7 2^29 3 0^1 (234 



MAY JUNE 



Average number of punctures per day by 10 beetles in insectary. 



Average maximum daily temperature in insectary. 



Worcester County, 1931 



The 1931 records from 38 orchards in Worcester County showed 20 per cent 

 better control in Baldwin orchards and 14 per cent better control in Mcintosh 

 orchards where the application was made on May 26, 27 or 28 than where the 

 sprays were applied after this date. It is interesting to note that with both vari- 

 eties of fruit the minimum infestation in orchards receiving a late application is 

 greater than the maximum infestation where a timely application was made. 



Table 8. — Percentage of Harvested Fruit Injured by Plum Curculio. 

 Worcester County, Mass., 1931 



Time of Application 



Infestation, Per Cent 



Variety 



Number of 

 Orchards 



Maximum Minimum 



Average 



May 26, 27, 28 

 May 29 to June 6 



/ Baldwin 

 (Mcintosh 



Baldwin 

 Mcintosh 



0.7 

 1.2 



12.6 

 7.3 



4.33 

 3.0 



24.85 

 17.88 



Middlesex County, 1931 



Similar records from 30 orchards in Middlesex County in 1931 showed a 

 gain of 14 per cent control in orchards sprayed on May 26, 27, or 28, compared 

 to those receiving later applications. No distinction between varieties is made 

 in these orchards, and there is considerable variation due, apparently, to location 

 and inconsistent thoroughness of application. 



