408 REPORT OF STATE BOARD OF HORTICULTURE. 



merely enters a resting stage to be again stimulated to renewed activity by 

 the fall rains, has as yet not been determined, although it has an important 

 bearing upon the means to be employed in controlling the disease as will be 

 shown later. 



THE FUNGUS THE CAUSE OF THE DISEASE, 



We have stated above that the disease is caused by the fungus Gloes- 

 porium malicorticis. It may be of interest to the orchardist to know upon 

 what evidence we base the assertion. It is not necessary to give at this 

 time all details of the work which have led us to the conclusion. In brief, 

 however, spores were induced to grow in artificial cultures. As they ger- 

 minated they were examined under the microscope, their positions carefully 

 marked, and when they had developed to such an extent that they could be 

 seen by the unaided eye, they were separated from all other growths and 

 transferred to tube cultures. This process was repeated many times and in 

 different ways to eliminate all sources of error. When convinced that no 

 other living organism was present in the tube 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 discolored areas 

 were observed about several of the points of infection, and in three weeks 

 these areas had developed all the characteristics of the disease as seen in 

 nature : being brown, distinctly depressed and separated from the surround- 

 ing living portions by the irregular ragged fissures. Having thus succeeded 

 in producing the disease by inoculating with the fungus, we are justified in 

 asserting that the fungus is the cause of the disease. 



REMEDIES. 



Before any experiments in controlling the disease could be intelligently 

 undertaken, it was necessary to know something of its nature. Having 

 shown that it is caused by a certain fungus, the question of most interest is, 

 can it be controlled ? And, if so, how ? My absence from the state, while 

 studying the fungus itself, necessarily prevented me from conducting any 

 experiments in controlling it, but from what I now know of the disease, I 

 believe that I may safely assert that it can be controlled. We have seen 

 that the spores are developed and probably distributed during the late sum- 

 mer and fall months, and that they undoubtedly germinate after the fall 

 rains begin. It is also known that bordeaux mixture and other copper 

 compounds prevent the germination of the spores of most fungi. We, there- 

 fore, infer, that if the trees be properly sprayed with bordeaux mixture, or 

 with the ammonical solution of copper carbonate, once soon after the fall 

 rains begin, and again as soon after the leaves fall as possible, the germin- 

 ation of the spores will be largely prevented and the spread of the disease 

 be thereby checked. It is not expected that such a process will exterminate 

 the disease, but it is believed that it will so reduce its ravages that it can no 

 longer be considered a menace to the a^jple-growing industry. For the 

 latter of the two applications mentioned above, bordeaux mixture, winter 

 strength, should be used. For the former, bordeaux mixture, summer 

 strength, may also be used, but if the fruit is on the trees it would be better 



