142 Bulletin 142. 



The above facts and observations lead us to believe that in applying 

 a poisonous spray soon after the blossoms fall, we deposit some arsenic 

 in the calyx cavity, where Nature kindly takes care of it for us until 

 ten days or two weeks later, when the little apple-worm includes it 

 in the menu of his first few meals. Furthermore, this poisoning of 

 these young worms, which enter the developing fruit in the spring, 

 seems to be the only way and the only time that the insect is or can 

 be most successfully reached with the spray ; as the worms sometimes 

 eat through into the calyx cavity from the outside at the base of the 

 lobes, and as some of the poison often, lodges here, possibly a few of 

 them get enough poison to kill them at this point. Not enough of the 

 spray can be made to stay on the surface of the fruits then or at any 

 subsequent time to reach one in a hundred of the worms which enter 

 elsewhere than at the blossom-end. Put in another way, the above 

 facts mean that we can hope to reach with a poison spray only those 

 apple- worms which enter the blossom- ends of the forming fruits in the 

 spring. To do this, the application must be made soon after the 

 blossoms fall, when the calyx is open, as shown in figure 145. If we 

 wait a few days until the fiiiit has reached the condition shown in 

 figm-e 146, or still later as at a and b in figure 131, it will be too late. 

 We can conceive of no possible way in which a majority of the 15 or 

 20 per cent, of the worms which enter the fruit at some other point in 

 the spring, and all of the worms of the subsequent broods, can be 

 effectively reached with the poison spray. 



Thus, while the spraying method is very effective, it can never 

 prove a perfect panacea, especially where there are two full broods or 

 more of the insect in a season. However, it is a great improvement 

 over the old banding method, for with the spray we kill the worms 

 before they fairly begin their destructive work, thus saving the fruit 

 they would otherwise ruin with an ugly worm-hole. Our observations 

 indicate that the httle worms do no feedincr on the outside of the fruit 

 except just enough to make a tiny entrance- hole into the flesh or into 

 the calyx cavity. If it were not for their habit of feeding in this blos- 

 som cavity for a few days, it is doubtful if spraying would be nearly 

 so effective as it is. It is thus a remarkable fact how much of our 

 success with a poison spray depends upon this habit of the little worms.* 



* We have never found any dead worms in the calyx cavity, and thus have 

 no absolute proof that they are killed by the poison there, but Munsou has 



