86 



about two weeks later, when the majority of the larvae are entering 

 the fruit. There has been much discussion recently in regard to dis- 

 pensing with the spraying immediately after the blossoms hav^e fallen. 

 It has been found that the larvae enter the fruit from one to two 

 months after the blossoms have fallen. In cases of bad infestation, 

 where preventive measures have been neglected, or there is an abun- 

 dance of the insect, it might be well to make three sprayings while the 

 second generation is entering the fruit. This period varies with the 

 locality and with the seasons in the same locality; but there are a few 

 methods ])y which the time can be approximated with sufficient accu- 

 racy, and in view of the fact that the time is variable the writer does 

 not wish to recommend that the spraying be dispensed with until each 

 locality is studied. Sprajdng may be begun immediately after the 

 first new entrance holes of the second generation are found, or about 

 twenty days after the date the maximum of the tirst-generation larvae 

 are found under the bands ready to spin their cocoons. The larvae of 

 the second generation in southern Idaho usually begin to enter the 

 fruit the last week in July, but the majority enter in August, and 

 but few in September. The number of sprayings to be made against 

 this generation depends entirely upon the success achieved against the 

 first generation. It has been found quite definitely that the injur}- due 

 to the second generation is much greater than that from the first gen- 

 eration; and if the injury due to the first generation is from 2 to 5 per 

 cent the writer advises a third spraj'ing for the second generation; 

 but if the injur}^ has been only 1 per cent or less, two sprayings will 

 be found sufficient. The quantity of lime used in these late sprajdngs 

 should }>e reduced to a minimum, as lime on the fruit depreciates its 

 market value. 



Light showers wash but little of the spray from the tree; but if 

 there is a heavy shower or continued rain, a large amount will be 

 removed, and it will be necessary to repeat the sprajangs as soon as 

 possible. Lead arsenate is less aflfected by rain than the other spray- 

 ing compounds. 



HOW THE POISON KILLS THE INSECTS. 



Though Paris green has been used for spraying purposes for manj^ 

 j^ears with success against the codling moth, it is only recently that 

 any serious effort has been made to ascertain how the poison is 

 obtained by the larvffi. Slingerland was the first to answer this ques- 

 tion with any degree of accuracy. According to him the spray lodges 

 in the saucer-like calyx when the }■ oung fruit is erect after the blos- 

 soms have fallen, and upon the segments or leaves of the calj^x clos- 

 ing the poison is held there for some time. As about 80 per cent of 

 the larva' of the first generation enter the fruit through the cal3'x, it 

 is easily seen how the majority of them would obtain some poison. 



