12 abstracts: phytopathology 



acid solutions of ferrous salt containing some ferric salt. The product 

 usually contained some crystals of disulphide. 



Troilite is only the end-member of the pyrrhotite series and not a 

 distinct mineral species. Thus far it has not been prepared free from 

 metallic iron. E. T. A. 



PHYTOPATHOLOGY.— The control of the chestnut bark disease. 

 Haven Metcalf and J. Franklin Collins. Farmers' Bulletin 

 U. S. Department Agriculture No. 467. Pp. 24, figs. 4. 1911. 



This bulletin describes the chestnut bark disease and recommends 

 methods for its control. This disease, caused by the fungus Diaporthe 

 parasitica Murrill, first came prominently to the public attention in 

 1904, and since that time has proved itself perhaps the most serious tree 

 disease known to science. First noted in the general vicinity of New 

 York City, it has now spread into at least ten States. It attacks the 

 American chestnut, the European chestnut, the chinquapin, and, rarely, 

 the Japanese chestnut; but so far has not been found growing parasiti- 

 cally outside of the genus Castanea. The total financial loss is now esti- 

 mated at $25,000,000. If the disease is not controlled thru human 

 agency, there appears to be no reason to doubt that the chestnut tree 

 will become largely extinct in North America within the next ten years. 

 The fungus gains entrance at any point where the bark is broken, 

 borers' tunnels forming the most common means of entrance. From the 

 point of entrance, the disease spreads primarily in the inner bark and 

 produces characteristic lesions which girdle the tree at the point attacked. 



Conspicuous symptoms are the development of bunches of sprouts 

 below the girdling lesions; the half-formed yellowish leaves in the spring 

 on the previously girdled branches; the reddish-brown leaves on branches 

 girdled in summer, and the yellow, orange, or reddish-brown pustules 

 of the fruiting fungus on the bark. It is practically useless to attempt 

 systematic location of the disease from October to April, inclusive. 



The spores may be carried considerable distances on chestnut nursery 

 slock, tan bark, and unbarked timber; also by birds, insects, squirrels, 

 etc., which have come in contact with the sticky spore masses. Water 

 quickly dissolves these spore masses and the minute spores are in this 

 way carried along with water, as, for instance, with rain water running 

 down a tree 



The only known practical way of controlling the disease in a forest 

 is to locate ami destroy the advance infections as soon as possible after 

 they appear and, if the disease is well established near by, to separate 



