Trees and Timber 



389 



surrounded by a border of dead tissue. Premature defolia- 

 tion results. The disease is prevalent in all parts of the 

 United States. 



FILBERT, HAZEL 



Blight '^'' (Bacteria). — A serious blight, which in many 

 respects resembles blight of pear, affects the filbert in Oregon. 

 It occurs on buds, shoots, leaves, and 

 as cankers on larger limbs. 



Black-knot ^^^ {Cryptosporella anom- 

 ala (Peck) Sacc.). — In 1892 Halsted 

 noted black-knot as destructive to sev- 

 eral hundred trees in New Jersey, and 

 in 1893 Humphry described the same 

 disease upon hazel canes in Massachu- 

 setts. It is characterized by numer- 

 ous small, elliptical, warty emergences 

 upon the bark of the diseased branches. 

 The diseased portions are sunken, 

 owing to the contraction of the inner 

 bark to a mere line. The girdling pro- 

 duced results in death of the affected 

 canes and general injury similar to 

 that produced by plum knot. Affected 

 branches should be cut and burned. 



Fig. 206. — Elm leaf- 

 spot. After Heald. 



HEMLOCK, WESTERN {Tsuga heter- 

 ophijlla) 



Heart-rot ^^^ (Echinodontium tindo- 

 rum E. & E.). — The fungus enters 

 through wounds, chiefly branch stubs, and produces a 

 stringy brown rot of the heartwood, which extends to all 

 parts of the tree. A single sporophore of the fungus on 

 the first 16-foot log of the tree trunk may be taken to indicate 

 that the heartwood is unmarketable in both the first and 

 second logs. The position of the largest sporophore usually 

 indicates the region of greatest decay. 



