188 MASS. EXPERIMENT STATION BULLETIN 170. 



practiced. All fertilizers should be ai)plied evenly. Spreading b}^ hand 

 is at best a poor method, as shown by the dark green plots of grass on 

 lawns where nitrate of soda has been applied in this way; but when 

 fertilizer spreaders cannot be had the hand method must be used. Another 

 factor to be considered when applying fertilizers to lawn trees is that the 

 grass roots will obtain their full share. Turning under the sod and cul- 

 tivation of the soil around the tree is of 

 the . greatest importance from the very 

 considerable amounts of organic matter 

 added to the soil. Fertilizers applied 

 under these conditions, or, far better, 

 stable manure well incorporated into the 

 soil at the rate of 20 to 30 cords per acre, 

 are of the greatest benefit to the tree, 

 even if it becomes necessary to reseed 

 immediately. In cases where it is incon- 

 venient or undesirable to disturb the 

 soil around a tree, and when the applica- 

 tion of fertilizer to the surface does not 

 accomplish the desired results, holes 1 or 

 2 feet apart and 15 inches deep may be 

 made with an iron bar and then filled at 

 different times with a liquid fertilizer. 



There are a numl^er of fertilizer mix- 

 tures prepared for shade trees that are 

 undoubtedly of value, but some of them 

 are apparenth^ not based on any expert 

 knowledge of the tree's special require- 

 ments. 



Fici. 61. — Reenforced wire cloth 



tree guard, showing edge stiffen- DISEASES OF TrEES. 



ing with nail holes for attaching 



to tree. (From the Wright Wire Trees, like other living organisms, are 



Company.) very liable to attacks from disease, and a 



tree of any maturity is seldom found 

 perfect in all respects. A disease may be defined as a disorder caused bj^ 

 any failure in or diversion of the normal phvsiological activities of the 

 organism. 



The diseases of plants with which plant pathologists have to deal may 

 be divided into three classes: First, those caused by parasitic fungi; 

 examples, — rust, smut, etc. Second, those brought about by functional 

 irregularities wliich induce saprophytes (dead wood fungi) or parasites 

 to thrive, such as "damping off," mildew, etc. Third, those of a purely 

 functional nature, pathogenic organisms not necessarily being present; 

 examples, — dropsy or cedema of tomatoes, malnutrition and others. 

 All these tj^pes of diseases are found in trees, but the first and second are 

 most common. 



