474 



ENCYCLOPEDIA OF PRACTICAL HORTICULTURE 



that all roots and stumps be carefully re- 

 moved from the earth in clearing, and 

 that before planting trees, the soil be de- 

 voted to other than orchard crops for 

 several years until the root-rotting fungus 

 has had a chance to die out. 



Evidence that much of the infection 

 takes place where trees are injured bj' 

 cultivation leads to the suggestion that 

 cultivation close to the tree be done with 

 greatest care to avoid injury. At the 

 same time thorough cultivation has been 

 advised in order to establish good aera- 

 tion of the soli, since this condition is 

 supposed by some to be unfavorable to 

 the progress of the disease while it un- 

 doubtedly promotes the vigor of the tree. 



When trees are once attacked by the 

 fungus, death, almost without exception, 

 is only a question of time. It seems use- 

 less, therefore, to retain in the orchard 

 trees which will be worthless to the own- 

 er and which may become a source of in- 

 fection for other trees. It has conse- 

 quently been considered best to grub up 

 at once any tree discovered to be diseased 

 and to remove it from the orchard, taking 

 out at the same time as much of the root 

 system as possible. It has also been ad- 

 vised not to plant another tree in its 

 place for at least three years. 



If it should seem desirable to retain 

 temporarily a tree known to be diseased, 

 it would perhaps be safest to dig a trench 

 about two feet deep around *he tree near 

 the tips of the roots in order to prevent 

 the rhizoniorphs. which rarel.y occur 

 deeper than this, from spreading to other 

 trees. Throw the dirt inside the ditch. 

 Where conditions are such that the dis- 

 ease appears to be spreading rapidly from 

 tree to tree, the heroic method of uproot- 

 ing healthy trees in advance of the zone 

 of infection has been suggested; but as 

 far as we know, the disease rarely as- 

 sumes such a condition in the Northwest 

 as to warrant so drastic a method of 

 treatment. 



On account of the possibility of infec- 

 tion from spores produced by the mush- 

 rooms, all fruiting bodies appearing at 

 the base of diseased or dead trees, or in 

 other places in the orchards and fields, 



should be collected while still in the but- 

 ton stage and destroyed by burning. 

 Knocking them over does not prevent 

 spore formation. 



The effect upon the disease of various 

 chemical substances worked into the soil 

 around a tree has never been thoroughly 

 tested out. This line of investigation may 

 prove to be worth while, and growers are 

 urged to make experiments upon trees 

 known to be affected. A record of the 

 exact treatment should be made and notes 

 kept regarding the effect in each case. 



Those who possess sufficient patience 

 and skill, and are willing to devote the 

 necessary time, may be able by the fol- 

 lowing method to save individual trees 

 that are not too far gone when the dis- 

 ease is discovered. This method has been 

 used in one Oregon apple orchard with 

 considerable success. Whether it can be 

 applied as well to other kinds of fruit 

 trees remains to be seen. At the first 

 sign of unhealthy foliage the tree Is ex- 

 amined for root rot. Where this is found, 

 the earth is removed from the base of the 

 tree and the main roots are exposed for a 

 foot or more. The soil is also removed 

 from beneath the roots. The air and sun- 

 shine have access in this way to the 

 crown and root bases. The dead portions 

 of the bark are carefully and completely 

 removed from trunk and roots. If a root 

 is girdled, it is taken out entirely. After 

 all the diseased parts of the tree are cut 

 out, the exposed surfaces are washed with 

 some disinfectant, such as Bordeaux mix- 

 ture or corrosive sublimate. When they 

 are dry, walnut grafting wax is applied. 

 Then, in order to restore as quickly as 

 possible the area of the trunk destroyed 

 by the fungus, bridge-grafting is resorted 

 to. A number of scions are inserted into 

 the healthy tissue of the trunk just above 

 the dead part, and their lower ends are 

 connected with healthy roots. This is a 

 delicate operation and the trees have to 

 be braced to prevent the scions from pull- 

 ing out. In an orchard recently visited 

 by the writer, a few young bearing apple 

 trees which were treated in this way two 

 years ago are now ai)parently free from 

 any trace of disease and as thrifty as any 



