46 MASS. EXPERIMENT STATION BULLETIN 315 



Efforts were continued to stimulate community action on the part of growers 

 within well-defined maggot control areas. Results again demonstrated the diffi- 

 culty of securing concerted action on the part of all the growers in any large area, 

 and that failure of any grower to carry out his assignment not only led to failure 

 to control the insect in his own orchard but did much to neutralize the efforts of 

 neighboring growers. 



There were several orchards where apple maggot appeared the past season for 

 the first time as a serious pest, in spite of thorough and supposedly well-timed 

 spraying. In most of these cases the trouble was directly attributable to the 

 removal of large numbers of neglected trees adjoining the orchards. Fruit from 

 these trees was badly riddled by maggot the previous season and led to the ap- 

 pearance of thousands of flies which necessarily moved into the commercial 

 orchards. In cases of such wholesale removal of neglected trees, it is essential 

 that in commercial orchards the complete spray program be carried out, at 

 least for the first season. Disposal of such trees, however, removes permanently 

 a very serious source of danger. 



In general there were three main factors which tended to increase the danger 

 of infestation of fruit in commercial blocks. 



1. A short crop, especially of Baldwins, due to winter injury and to the 

 heavy Baldwin crop of the previous year. 



2. The CWA project of removal of neglected trees adjoining orchards. 



3. The tendency on the part of many growers to apply a complete spray 

 program only to the trees in fruit. 



A combination of any or all of these factors rendered the control of apple 

 maggot particularly difficult this past season. Most of these, however, were 

 peculiar to the past season and would not normally be expected to exert so much 

 influence in 1935. 



Valuable data on the influence of different soil conditions and of exposure 

 upon the emergence of the adult flies were secured from cage experiments at the 

 Waltham Field Station by Professor Whitcomb. These are summarized as 

 follows: 



Date of Emergence of Apple Maggot Flies, Waltham, 1934 



In Sun In Shade 



Cultivated Sod Cultivated Soa 



Light Soil 



1st fly June 22 July 3 July 6 



25% flies July 9 July 15 July 16 



50' ; flies July 15 July 20 July 22 



75% flies July 18 July 25 July 27 



Heavy Soil 



1st fly July 1 July 14 July 9 July 10 



25% flies July 16 July 23 July 20 July 23 



50% flies July 19 July 26 July 24 July 26 



75% flies July 22 July 29 July 28 July 30 



These results show the difference to be expected in the emergence of the flies 

 in cultivated orchards and those in sod, and in heavy soil as compared with light 

 Flies appeared earlier from soil exposed to direct sunlight than from soil in shade. 

 These figures do much to explain the very uneven appearance of flies in commer- 

 cial orchards because of the removal of near-by neglected trees during the pre- 



