INDIANA HORTICULTUKAI, SOCIETY. 423 



"The most fertile source of infection is certainly found in the several 

 sorts of mycelial strands produced by this fungus. The subcortical my- 

 celium is an old stump or even a diseased tree may give rise to the pur- 

 plish-black rhizomorphic sti-ands, and these will grow out in the soil to 

 a considerable distance. In one case the author was able to trace these 

 subtei-ranean strands for a distance of about ten feet from a partially de- 

 cayed oak stump. One of these same strands was followed, at an average 

 depth under the surface of the soil of ten inches, where it was found 

 entering the cortex of a living 'Ben Davis' apple tree. None of the other 

 roots of this tree were diseased, and it was plain that the first entrance 

 of the mycelium had been made at this point, out on one of the smaller 

 roots at least six feet from the trunk of the tree. 



"Though the first entrance to the tree is generally made by the my- 

 celium through the cortex of a small root, yet cases were found in which 

 the mycelium had evidently entered the crown of the tree first, and then 

 spread out through the smaller roots and up into the trunk. As a rule, 

 the mycelium does not grow up in the trunk above three feet from the 

 crown. In fact, in many cases no trace of the mycelium can be detected 

 in the trunk more than five or six inches above the crown. 



"The greater part of our knowledge concerning the proper remedial 

 measures to be applied against this and other wood-destroying fungi is 

 derived from the wide experience of the foresters of Europe. Among the 

 strictly remedial measures none are of greater importance than the isolation 

 of diseased trees by ditching. If a single tree in the middle of the orchard 

 IS found to be diseased, a ditch should at once be dug around it to pre- 

 vent, if possible, the further spread of the disease by the subterranean 

 mycelial strands. This ditch should be dug at a distance of about ten 

 feet from the tree, i. e., with a diameter of about twenty feet. The ditch 

 should be about one foot wide and about two feet deep with vertical walls. 

 The same measures are to be adopted to protect a group of diseased trees 

 that are found in the orchard. In this case the ditch may be dug so as 

 to include all the trees in the gi'oup. It is possible that the burning of 

 brush in this ditch will kill the rhizomorphic strands and prevent further 

 spreading. So far as the author is aware this method has never been 

 practiced to any gi-eat extent in America, though in Europe it seems to 

 have proven effective in combating this and similar diseases. 



"It can not too strongly be insisted upon that all fruit trees that are 

 found to be diseased should at once be removed from the orchard. Care 

 must be taken in such cases to remove and burn not only the trunk, but 

 all the larger roots and especially all those diseased. Perhaps a tree will 

 bear salable fruit after the mycelium of this fungus has entered its root 

 system, but it is a near-sighted system and poor business to allow such a 

 tree to stand when it is remembered that thereby all the other trees in 

 the orchard are being endangered. 



