lO MAINE AGRICULTURAI, EXPERIMENT STATION. 



more effective is a spring treatment of the young oyster shell 

 bark scale which can be killed in June and early July by spray- 

 ing with kerosene emulsion, strong tobacco solutions, or other 

 materials of like nature. These are not designed for internal 

 poisons but kill the insects by contact. Hence in their applica- 

 tion it is the insects themselves and not the tree or the foliage 

 or fruit that the substance must reach. It requires greater care 

 to apply insecticides for sucking than for eating (chewing) 

 insects. The apple plant louse does large damage in many 

 Maine orchards. Many insecticides have been tried. Kerosene 

 emulsion is eft'ective but unless properly made and applied under 

 favorable conditions it discolors the fruit, and is likely to do 

 serious damage to the foliage. The aim is to get an insecticide 

 that will kill the aphids and leave as little trace of itself on 

 fruit and foliage as possible. Tobacco solutions come the near- 

 est to meeting these requirements of any thing tried. 



Studies of Apple Diseases. 



The diseases of the apple other than those produced by 

 insects naturally divide themselves into two classes — those 

 which are caused by plant parasites such as fungi and bacteria, 

 and those which are of a non-parasitic nature, that is physi- 

 ological diseases or those produced by unfavorable conditions 

 of the environment. For convenience a discussion of what 

 this Station has done in the study of the latter class of diseases 

 will be given first. 



non-parasitic diseases. 



Winter Injury. The first observations recorded by this Sta- 

 tion on winter injury were made in 1900 and 1901. This was 

 the coldest winter known here for twenty years. The mercury 

 on one occasion went to — 36° F., while the mean temperature 

 for December was 12° -F. In the preceding season trees on 

 the warm, rich soils failed to mature new growth. Consequently 

 when the severe winter weather followed trees which should 

 be hardy in our climate were either killed or severely checked. 



At this time, it was pointed out that an all important requisite 

 of hardiness is that wood should complete its growth early and 

 become well matured before cold weather. Therefore, orchards 



