96 Report of State Board of Horticulture. 



the anthracnose spots is slow, but in the spring the mycelium 

 takes on a renewed activitj^ which is shown by the rapid 

 increase in size of the cankers. In May and June the fungus 

 reaches the fruiting stage and from that time on all its en- 

 ergies are devoted to the production of spores. The canksrs 

 then cease to increase in size and become surrounded by 

 ragged fissures. Soon the mycelium dies, the wound begins 

 to heal by the formation of new cellular tissue and in the 

 course of months the dead bark sloughs off, exposing the 

 ugly wound. 



PROOF OF ITS FUNGUS ORIGIN. 



We have stated above that the disease is caused by the 

 fungus Gloesporium malicorticis . It may be of interest to 

 orchardists to know something of the evidence upon which 

 w^e base the assertion. In brief it is as follows: Spores 

 were induced to grow in artificial cultures. As they germin- 

 ated they were examined under the microscope, and when 

 they had developed so that they could be seen by the unaided 

 eye, they were separated from all other growths and trans- 

 ferred to other artificial cultures. This has been repeated 

 many times and in different ways to eliminate all sources of 

 error. When convinced that no other living organisms were 

 present in the cultures a number of sections of apple limb 

 were inoculated with this "pure culture" of the fungus. In 

 about a week after these inoculations were made slightly dis- 

 colored areas were observed about several of the points oi 

 infection, and in three weeks these areas had developed all 

 the characteristics of the disease. This was the preliminary 

 work. Later, twenty young apple trees in the College orchard 

 were inoculated with similar cultures. Every tree developed a 

 typical case of anthracnose. Fig. 10 is from a photograph 

 of one of these trees which had been girdled by the disease 

 and the top killed. Fig. 7 is also a photograph of a section 

 of one of these trees taken about a year after the inoculations 

 were made, to show the wound and the formation of callular 

 tissue. These experiments have been repeated many times, 

 and almost invariably result in the development of typical 

 cases of anthracnose. 



