232 Report of the Horticulturist of the 



There are only a few diseases that are widely distributed in the 

 raspberry plantations of New York. Of this number, orange rust 

 and anthracnose are particulary troublesome. Orange rust is 

 easily recognized by the bright orange color that its masses of 

 spores give to the underside of the leaves or other growing parts 

 of the plant on which they chance to form. Anthracnose, how- 

 ever, is not so easily recognized and so is all the more dangerous. 

 Great confusion exists in regard to the appearance of this disease 

 and its effect on the plant, so a somewhat extended popular de^ 

 scription is given. 



What are plant diseases? — In order that we may more readily 

 grasp the discussion let us consider briefly the nature of plant 

 diseases. The fungi that cause plant diseases are minute plants 

 of low order that live as parasites on higher plants. It requires 

 the assistance of a powerful microscoi^e to make out the char- 

 acters of most of these tiny plants, yet they are just as truly 

 plants as are the trees upon which some of them live. They 

 have organs called mycelium that correspond to roots and modi- 

 fied branches of the mycelium bear minute bodies called spores, 

 that are similar to and perform the same office as seeds. Under 

 favorable conditions of moisture and temperature the spores are 

 borne in innumerable quantities and they readily germinate under 

 the same conditions. The spores are very small and light so are 

 borne on the slightest breath of air. Scattered by the winds or 

 other agencies the disease spreads rapidly when the weather 

 conditions are suitable. 



What is anthracnose? — The name anthracnose is a popular term 

 that has come to be applied to plant diseases that are caused by 

 one of the two groups of fungi known as Colletotrichum or 

 Gloeosporium. The anthracnose of the raspberry belongs to the 

 Gloeosporium group. The different species of this genus attack 

 their host plants differently. ^The one that lives on raspberries 

 may attack any part of the plant but is more commonly found on 

 the canes and it spreads principally by attacking the young 

 shoots. The fungus remains dormant during the winter on the 

 canes but as soon as suitable weather comes in the spring, spores 



