CONTROL OF DISEASE. 61 



scattered and harmless condition. Parasitic fungi and 

 mistletoes, on the other hand, develop rather slowly, 

 and spread their activity over long periods. Sudden 

 outbreaks of disease, regular epidemics, are rare. The 

 only sudden danger might come from leaf, twig, bark, 

 and root diseases. 



Prevention is the basis of control of parasitic fungi 

 and mistletoe. The greatest difficulty lies in the fact 

 that the spores of injurious fungi are found everywhere, 

 being carried long distances by air currents. It follows 

 that fruiting bodies of parasitic tree fungi should be 

 destroyed by fire, if possible, wherever found. A young 

 tree whose stem is affected with mistletoe can never pro- 

 duce a straight, sound trunk. It is therefore better to 

 destroy it, in order to make room for sound reproduc- 

 tion. A mistletoe-infested branch should be cut off 

 some distance from where the mistletoe appears, since 

 its roots may spread rather far toward the trunk in the 

 living bark. Trees with infected stems or trunks can 

 not be saved. 



The practice of cutting mistletoe-infected trees out- 

 side of timber-sale areas would, of course, be practicable 

 only along roads and trails. More systematic and valu- 

 able work can be done by every ranger around his 

 regular station. Just as the neatness and cleanliness of 

 an office would always speak for the quality of the 

 ranger who is in charge of it, so the clean and healthy 

 condition of the forest about the ranger station should 

 testify to the ranger's credit. Ranger sales and free 

 use are means by which the ranger can very materially 

 help in establishing healthy conditions on the forest 



