FOOD SUPPLY 



59 



careful studies of the life history and habits of specific insects 

 have greatly extended the field of usefulness of the arsenical 

 insecticides. This is well illustrated by studies made on the 

 codling moth by Melander. This insect is a very important 

 enemy of the apple, within the fruit of which its develop- 

 mental stages are passed. It is usiudly controlled by spray- 



Fig. 28. Chart illustrating the effects of spraying with lead arsenate by different methods for the 

 control of the codling moth {Carpocapsu ■pomonella), a widespread and serious insect enemy of the apple. 

 In this case unsprayed trees yielded only 40 per cent of good fruit, while of the wormy fruit, 80 per cent 

 became wormy from larvae entering the fruit at the calj-x cup; when sprayed with a Vermorel nozzle 

 giving a mist spray, 85 per cent of the fruit was good, while of the wormy fruit 40 per cent became 

 wormy from larvae entering at the calji cup; when sprayed with a Bordeaux nozzle giving a forcible, 

 penetrating spray, 9i per cent of the fruit was good, while of the wormy fruit 25 per cent became wormy 

 from larvae entering at the calj-x cup; when sprayed with a Bordeaux nozzle set at the proper angle by 

 means of a crook. 97 per cent of the fruit was good, while of the wormy fruit 5 per cent became wormy 

 from larvse entering at the cal.\T cup; finally, when the latter spra>nng was done from a movable tower, 

 99 per cent of good fruit was obtained and no apples became wormy from larvte entering at the calyx 

 cup. (After Melander.) 



ing the young fruit with an arsenical, but the advantage 

 gained varies within very wide limits depending upon the 

 exact time at which the spray is applied, the method of appli- 

 cation, and the type of nozzle used. Slight modifications in 

 the form of calyx cup of the young apple, due apparently to 

 different climatic conditions, have in turn a profound influ- 

 ence upon the efficacy of the spray, and in some regions, 

 several sprayings must be substituted for the single one 

 found to be effective at other places (Fig. 28). 



