180 THE MONTHLY BULLETIN. 



ably be a safe guess that there is more than one Armillaria spot to 

 every ten acres of mature bearing orchard. There are some orchardists 

 who are still ignorant of the nature of the trouble and since there is 

 much changing of ownership and control, especially of smaller orchards, 

 it very frequently happens that a man comes into possession of an 

 orchard in which there is oak fungus trouble, who is not aware of the 

 nature of the trouble nor of the previous history of his land. Land is 

 high priced and must yield an income. The search for profitable crops 

 to plant in any small vacant area is one which seems to be very poorly 

 worked out in most situations, especially since a large part of the fruit 

 growers are unwilling to engage in the growing of vegetables or inten- 

 sive truck crops. It is perfectly natural that small vacant areas 

 should be planted into nursery, since this is one of the most intensive 

 and promising ways of utilizing small areas. For these reasons it is 

 particularly liable to come about that Armillaria spots may be used for 

 the growing of nurseries. 



HOW THE FUNGUS ATTACKS THE ROOTS. 



The Armillaria or oak fungus attacks the roots of perfectly healthy 

 trees by sending out dark brown, cord-like structures from decaying 

 wood in the soil. These cord-like bodies or rhizomorphs bear consider- 

 able resemblance to roots until they are closely examined. When they 

 come in contact with a living root the very minute fungous threads of 

 which they are composed grow out and penetrate into the substance 

 of the root. At first there is very little indication of anything wrong, 

 but soon the root in the immediate proximity to the rhizmorph becomes 

 stained and later begins to puff up and frequently there is exudation 

 of gummy material. If now the puffed and diseased root is cut into 

 or the bark lifted, white conspicuous mycelial bodies will be found 

 below the surface, and it will be seen that the tissue of the root is 

 being attacked and destroyed. This process, however, goes on rather 

 slowly, so that when nursery trees are planted in proximity to old, 

 infected roots in the soil the fungus may not come in contact with 

 the roots of the young trees for the first year, and after coming in 

 contact with them it works rather slowly so that not enough roots 

 will be destroyed to cause the death or even serious checking of the 

 growth of the "young trees for probably the first few years. But once 

 established in the roots it continues to grow and will not cease under 

 normal conditions until the tree has been killed, so that the infected 

 tree might easily be lifted and carried to a distant orchard, planted, 

 grow for one, two or several years, and then die with typical root rot. 



THE CRITICAL STAGE. 



It would seem possible by careful inspection to reject all infected 

 trees, but in examining infected roots I have come to the conclusion 

 that there is still a chance of transferring the disease in spite of most 

 competent and conscientious inspection. What seems to me to be the 

 critical stage is the early time of infection. Let us suppose that a 

 rhizomorph has come in contact with the root, that the delicate threads 

 of the fungus have commenced to penetrate into the bark but have 

 not yet caused a visible blistering or killing, but have established 

 themselves in the tissue of the root. It would be very easy indeed 



