340 MAINE AGRICULTURAL EXPERIMENT STATION. I9IO. 



cussion of the various insect parasites of Maine orchards and 

 the means by which they may be controlled the reader is referred 

 to a circular recently published by this Station on the Apple 

 Tree Insects of Maine. 



In this State fungi are responsible for the major part of the 

 loss from the diseases under consideration. Fungi are low 

 forms of plant life made up of threads of microscopic size. 

 These threads constitute the mycelium of the fungus, which 

 penetrates into the tissues of the host, causing the death of the 

 cells which compose these tissues and living upon their con- 

 tents. The conspicuous portions of the fungus which are seen 

 on the surface of the host are in most cases the fruiting organs. 

 Instead of seeds these fruiting organs produce various forms 

 and in various ways, often in vast numbers, more simple bodies 

 which are known as spores. 



In combatting apple diseases caused by fungi, the chief object 

 is to prevent the formation of these spores, or if they are formed 

 to destroy them before they can germinate and gain a foothold 

 upon healthy fruit, foliage, or wood. This is more frequently 

 brought about by destroying the diseased portions as soon as 

 observed and by coating or spraying the healthy parts with some 

 substance which will prevent the germination and destro}' the 

 spores if by chance they fall thereon. 



The threads of many fungi are colorless, while others are 

 more or less colored or darkened, but all are devoid of the green 

 coloring matter which enables the higher plants to manufacture 

 their food substances, through the aid of energy obtained from 

 sunlight, from the simpler compounds which they get from the 

 air, soil and water. Hence fungi and bacteria which are also 

 deficient in green coloring matter must depend upon more com- 

 plex organic bodies to supply their food materials. Through 

 the action of various ferments which they produce, parasitic 

 fungi can break down and destroy, with varying degrees of 

 ability, the tissues of their host plants. The results of this 

 decomposition furnish them the food materials necessary for 

 their maintenance and growth. The threads of a wood destroy- 

 ing fungus may be penetrating deep into the interior tissues of 

 an apple tree, causing their death and decay with very little 

 evidence of disease upon the surface. In fact the conspicuous, 

 external symptoms do not as a rule appear till the fungus has 



