No. 4.] FUNGOUS DISEASES. 91 



fungus pass uninjured through the alimentaiy canal of the 

 animals, are carried with the manure to the compost heap, 

 and thence are spread broadcast over our fields and orchards ; 

 and then we wonder that our summer treatment of the trees 

 with fungicides is of so little avail. The only reasonable 

 method to pursue is to gather carefully at the time of harvest, 

 and at once burn, all diseased fruit and leaves. 



But, as you know, fungi are not reproduced entirely by 

 their spores. In a great many cases the vegetative portion 

 exists perennially in the, twigs and branches attacked, as well 

 as in the discarded fruit, and is capable of propagating the 

 fungus upon the return of favorable conditions. In the 

 former case the unsparing use of the pruning knife is the only 

 reasonable cure. Familiar examples of such are the " black- 

 knot" of plum and cherry trees, in which case it is only 

 necessary to watch the growth of one of the ' ' knots " from 

 year to year to convince yourselves that it renews itself 

 annually from within the tissues of the branch ; the dreaded 

 " anthracnose " of raspberries, grape vines, etc. ; also all of 

 our more common " rust" fungi. Only by cutting out and 

 burning all diseased tissue can such diseases be eradicated. 

 The destruction of wild plants wdiich harbor dangerous para- 

 sites is another point of hygienic importance. Thus we can 

 best protect our cherries from "black-knot" by destroying 

 neigh])oring wild cherry trees infected with the disease, while 

 the ' ' rust " of apple leaves may be completely eradicated by 

 the destruction of adjacent red cedars, w^hich harbor, in a 

 peculiar form, the winter stage of the fungus. 



Furthermore, most fungi require a considerable degree of 

 moisture for their most rapid development. An unusually 

 warm, damp season is accompanied by great fungous activity, 

 and plants containing much water are peculiarly liable to 

 fungous attack. This is perhaps more noticeable, and at the 

 same time more readily controlled, in the greenhouse than 

 in the field. In such cases thorough drainage, and the train- 

 ing of the plants so as to secure free ventilation and the 

 access of air and sunlight, will do more to prevent diseased 

 conditions than any fungicide. 



I would also call 3'our attention, in this connection, to the 

 advisability of producing and selecting varieties of fruits, 



