146 Bulletin 142. 



and no injury resulted. The experiment was repeated later with the 

 same result. Next three sheep were kept till hungry, and then put in a 

 pen made under another tree which had just been sprayed. All of the 

 grass was eaten with no injurious results. This experiment was twice 

 repeated with the same result. Thus practical experiments confirm the 

 conclusions of the chemist. 



As no poison is usually sprayed on the fruit after it is half grown, 

 the rain and wind would naturally remove the last particle of it before 

 the fruit was picked. Chemical analyses have shown that there was 

 not the slightest trace of arsenic on the mature apples which had 

 been sprayed several times when they were small. 



JV/iy the spray may not be so effective on pears. — Several fruit- 

 growers have asked us to explain why they were unable to control the 

 codling-moth on pears as effectively as they do on apples. We can 

 only offer the following suggestions on this point. Our observations 

 on the young pears after the blossoms fall show that the calyx lobes 

 never draw together as they do on most varieties of apples (see figures 

 145 and 146). While it would thus be just as easy to lodge some 

 poison in the blossom-end of pears, the fact that the calyx cavity 

 remains open or unprotected would permit the poison to be easily 

 washed out by rains or blown out by winds. Whether the recently- 

 hatched apple- worm has similar habits when born on a pear as it does 

 on an apple, we cannot say from observation. Possibly, however, the 

 fact that the calyx cavity is open, may cause the worms to enter the 

 fruit at once, thus taking but few if any meals in the blossom end. 

 Thus the fact that it will doubtless be more difficult to keep a dose of 

 poison on pears, owing to the open calyx, may partially explain why 

 it may be more difficult to control the insect on this fruit. 



In 1874, Riley recorded that experiments in Illinois had shown that 

 pears were mostly injured by the second brood of the apple-worms. 

 Washburn recently reached a similar conclusion from his observations 

 in Oregon. As it has been shown that we can reach but few of the 

 worms of the second brood on apples with a poison spray, it is evident 

 that a similar treatment on pears would have httle effect, providing that 

 most of the injury to pears is done by the second brood of worms. 

 Perhaps we have been spraying too early for the insect on pears. 

 Wherever it does serious injury to pears, it would be well to make 

 some careful experiments with the poison sprays. 



