TAVENTY-NINTH FRUIT-GROWERS' CONVENTION. 



165 



can be no doubt, therefore, that in some manner the poison that was 

 on the surface of the apple reaches the worm after having gained 

 entrance to the fruit. How this can be accomplished can be explained 

 in one or two ways: Possibly there is a gradual solition of the arsenical, 

 the material spreading itself over the surface of the fruit and some of 

 it finding its way into the burrow and there being eaten by the worm. 

 One would expect, if this were true, that the worms should show signs of 

 chronic poisoning rather than be killed outright, which appears to be 

 the case. The second possible explanation is that the worms after 

 entering the fruit get out to the surface again and obtain the poison in 

 larger quantities. According to our observations this seems the more 

 probable. A single particle of the green would, probably, be sufficient 

 in the young codling-moth to produce violent poisoning. It is a matter 

 of positive observation that comparatively large areas of this surface 

 immediately adjacent to these burrows are eaten off by the insect. This 

 is true of both sprayed and unsprayed trees, and it is only after the 

 insect has increased considerably in size that it penetrates deeply into 

 the fruit. A rather complicated burrow is made immediately beneath 

 the skin of the fruit, and while it lives in this surface burrow it feeds, 

 in part at least, upon the surface of the apple. It is during this period 

 of surface feeding that the destruction of the worm is liable to happen. 



A microscopical study of sprayed leaves shows that the particles of 

 green are really found only at rather distant intervals upon the surface 

 of the leaf and fruit, and unless the insect feeds over a comparatively 

 large area of the surface it is difficult to understand how it would 

 obtain the poison in sufficiently large number of cases to account for 

 the efficiency of spraying operations. The surface eaten over, however, 

 by a young codling-moth larva, as described above, is amply sufficient 

 to enable it in most cases to find one or more particles of the poison on 

 a well-sprayed tree. 



The practical bearing of these observations upon the spraying oper- 

 ations is that they emphasize (1) the advantage of filling the blossom 

 cup in any except in semi-immune areas, like a portion of the Pajaro 

 Valley; (2) the importance of covering the whole tree with poison in 

 order to reduce, as far as possible, the number of entrances, since each 

 entrance means a blemish on the fruit; (3) the benefit of continuous 

 work season after season, so as to keep the insects down to as low a 

 number as possible, to further diminish the number of entrances; and 

 finally, (4) during the whole period when the eggs are being laid the 

 need of extreme care in the spraying, so as to keep the fruit thoroughly 

 and uniformly covered with the poison. 



