10 



These rhizomorphs are part of the vegetative body of the mushroom. 

 The disease spreads by the spores produced on the mushrooms and b\' 

 the rhizomorphs which grow along the roots of the affected trees and 

 thus reach adjoining trees. No remedy is known for the disease, 

 which is nearly always fatal, at least to prunes. The only real method 

 of control is to dig up the affected trees, roots and all, and burn them. 

 No new trees should be planted in the same spots for several years. 

 An affected tree, if not at once dug up, should be isolated from adjoin- 

 ing trees by a ditch a foot wide and two feet deep. In any case the 

 mushrooms should be gathered and destroyed when the}^ appear. This 

 particular kuid is edible. Some growers have tested the efficacy of 

 lime, placing it in considerable quantity about the roots of an affected 

 tree, and it is claimed that in some cases the trees recovered. There 

 is room for considerable investigation in testing the usefulness of 

 lime, of Bordeaux mixture, and of other substances in this manner, 

 though the chances are that none of them will prove satisfactory 

 remedies. 



In addition to the above, the prune especially is subject to two 

 obscure ailments which are not caused by either insects or fungi. One 

 of these is called "leaf curl," and is characterized by the leaf margins 

 rolling in loosely toward the midrib, and usually becoming more or 

 less 3''ellowish. In bad cases many of these leaves fall off, and some- 

 times, at least, man}^ of the prunes as well. The trouble usually occurs 

 in July and August and seems due primarily to drought. At least it is 

 common to see it in some orchards while absent from adjoining ones; 

 and, in the same orchard, it may f requentl}' be noticed that the trees 

 in moister situations are normal in their appearance while the rest 

 are affected b}" the "curl." This view is held b}" many orchardists, 

 and the fact that the prune is thus affected in eveiT part of the North- 

 west where it is cultivated lends considerable weight to the conclusion. 



It is a noticeable fact, however, that some individual trees are more 

 subject to the trouble than others. Where this is the case it is usually 

 easy to find some secondary cause, such as injury to the crown by 

 borers or b}^ the mushroom disease, partial girdling due to the bark 

 bursting, or an imperfect union of the scion and stock. 



The other trouble is locally known as bark bursting, and seems con- 

 fined to the Coast region. It was particular!}' prevalent in 1899. It is 

 characterized by the splitting of the bark in an irregularl}^ longitudinal 

 direction, and not rarel}^ being torn awaj' from the wood for some dis- 

 tance on each side of the split. So far as observed, this occurs only 

 in late winter or just })efore the buds burst in spring. 



A curi-ent idea in regard to the trouble is that it results from the 

 tree being bark bound, and a common practice based on this idea is to 

 slit the bark from the branches to the ground. It is also claimed that 

 leaf curl is a result of the tree's being bark bound and that the slitting 



