MONTANA EXPERIMENT STATION. 207 



to state definitely the cause of the failure of remedial treatment, but 

 there is some reason to believe that in Montana a large majority of 

 the larvae arrive after the buds have opened enough to allow 

 them to crawl into the narrow cracks between the expanding leaves. 

 It is instinctive with these larvae to get out of sight as soon as pos- 

 sible, and once inside the opening buds with a few leaves tied to- 

 gether into a nest, sufficient food for the remainder of the larval life 

 is protected in such a wa}^ as to make it difficult, if not impossible, to 

 get the poison in contact with the food. ** 



If on arriving at the bud, the larvae finds its sufficiently open to 

 allow it to crawl in, in all probability very little food is taken from 

 the surface parts. If, on the other hand the bud is still closed, more 

 or less of the surface is eaten in boring to the center. If the part of 

 the bud through which the larvai eats its way is coated with a pois- 

 on, a fatal dose may be taken but at this season of the year the buds 

 are very rapidly swelling and a bud that is well coated one day may 

 two days later, on account of the expansion of the surface parts, be 

 so insufficiently covered as to be harmless to the larva that enters it. 

 As is well known to all fruit growers, some trees expand their leaves 

 earlier than others, and again peach buds open before most apple 

 buds. 



Again, after the bud may be said to be fully expanded the inner 

 terminal growing shoot continues to put forth new leaves. These 

 leaves are the ones that form the food of the larvae and they expand 

 within the nest where they are not easily reached with a spray. 



Considering how admirably the insect is protected by nature and 

 its own habits, its control when in its spring nest is at least un- 

 certain. 



The problem is less perplexing when only nursery trees or trees 

 in a young orchard are concerned. Under such circumstances hand 

 picking of the nests should be very satisfactor}^ In picking the 

 nests, however, care should be taken not to allow the larvae to es- 

 cape to the ground for they would probably return to the trees. A 

 pail, not a basket, shold be used in gathering the nests, which should 

 be burned or thoroughly saturated with kereosene oil. If left in a 

 pile at the side of the field, the chances are that some of the larvae 

 would complete their development to the moth and fly to the trees. 



