340 



Bulletin 263. 



Atkinson ('01) has shown that some fungi producing heart rot can- 

 not gain entrance to the tree except the hving layer be removed, as in 

 the case of a wound. The heart wood of a tree is dead and it is in 

 this that the semi-parasite gets a footing. Longitudinal and cross sec- 

 tions of an old diseased grape stem (Figs. 54, 55) show that the fungus 

 has developed in a very similar way ; very slowly and each year adding 

 a new circle of diseased wood. The cambium layer or growth area 



tries to heal over the wound, but is 

 irritated by the action of the fungus 

 and develops the corky excrescences 

 instead. Eventually, the stem is com- 

 pletely girdled and the vine dies, but 

 during this process exhibits some one 

 or all of the various phases mentioned 

 under signs of the disease. 



Distribution through diseased stock 



But now comes an even more seri- 

 ous consideration. It has been possible 

 to obtain pure cultures of the Fusi- 

 coccum by stripping back the bark of a 

 green shoot and removing under ster- 

 ile conditions a bit of the diseased tis- 

 sue to sterilized stems (Fig. 53). It 

 would seem quite probable then that 

 the fungus might readily live over 

 the winter in such places and continue 

 its growth the following year. If such 

 is the case and diseased canes were used for cutting they would even- 

 tually yield diseased vines. 



Some nurserymen practically trim a vineyard for the privilege of 

 carrying away the brush for cuttings, while in other cases owners make 

 the cuttings and sell to the nurserymen by the thousand. In either case, 

 no attempt is made to sort out the diseased canes, since the spots on 

 the canes are not regarded as having any connection with a disease. 

 Thus it is to be expected that the nurserymen often use diseased mate- 

 rial for stock. This is also more probable when the very general dis- 

 tribution of this disease is noted. The progress of this disease is 



Plioto. June 22. 1908 



Fig. 56. — Concord. An apparent- 

 ly healthy renewal, four years 

 old. The old trunk, which was 

 diseased, was pruned off last 

 winter. 



Vox) Atkinson, G. F. Studies of some Shade Tree and Timber Destroying 

 Fungi. Cornell Univ. Agr. Exp. Sta. Bull. 193: 199-235. 1901. 



