442 



ENCYCLOPEDIA OF PRACTICAL HORTICl'LTURE 



study many of the results of previous 

 workers have been confirmed and some 

 important points added to our knowledge 

 of the life history of the causal fungus. 



Early in the work a search was made 

 for a possible ascogenous stage in the 

 life history of the fungus. In November, 



1909, while studying the characters of 

 "two year old" cankers, that is, cankers 

 resulting from infection in the fall of 

 1907, the apothecia of a discomycete be- 

 longing to the family Mollisiaceae 

 were found occupying the position of the 

 acervulus of the previous season (1908). 

 (See Fig. 1-B.) Careful search revealed 

 the fact that the apothecia of this fun- 

 gus were nearly always found in the 

 dead bark of cankers one year after the 

 development of the conidial stage. The 

 writer has had this fungus under ob- 

 servation now for four seasons and has 

 never failed to find it in the bark of 

 cankers two years after infection in any 

 orchard in which he has searched at the 

 proper season. No other ascomycete has 

 been found at all constantly associated 

 with the cankers. We have also ob- 

 served the same discomycete in the old 

 bark of cankers on pear trees. 



Cultures obtained by most careful 

 methods from the germinating ascos- 

 pores were used to inoculate healthy 

 Spitzenburg apple trees. In all cases 

 cankers resulted which were character- 

 istic of apple tree anthracnose. The in- 

 oculations were made on December 12, 



1910, and in September. 1911, nine 

 months after the inoculation, cankers 

 resulting from the inoculation were ex- 

 amined and found to bear the typical con- 

 idia of this disease. In this way it was 

 proven that the fungus found in the old 

 cankers was the perfect or ascogenous 

 stage of the imperfect or conidial fungus. 

 Gloeosporium. malicnrticis. This ascomy- 

 cete was found to be undescribed and the 

 name Neofabraea malicorticis (Cordley) 

 was given to it by the writer (1913). 

 The economic importance of the discov- 

 ery of this perfect stage lies in the fact 

 that it proves that the old cankers are a 

 source of infection, as well as the new 

 cankers. It has also been shown that 



occasionally conidiospores are also de- 

 veloped on these same cankers, around 

 the edges of the apothecia of the perfect 

 stage. We have also determined that 

 conidia may be developed in the bark of 

 cankers three years after infection. 



Kinds of Trees Affected 



The disease was first recorded on the 

 apple, and for some time the fact of its 

 occurrence on other hosts was not ob- 

 served, or at least did not attract atten- 

 tion. Lawrence (1904) was the first to 

 record the occurrence of the disease on 

 the pear. He also produced the disease 

 by inoculation on this host. Cate (1908) 

 was first to record the disease upon the 



Fig. 3. Cankers on Pear Branches. 



quince. It has since been found to de- 

 velop abundantly upon the quince, though 

 recent developments indicate that the 

 fungus on that host may be due to a dif- 

 ferent species. It has been found not un- 

 common on the pear, particularly on the 

 Winter Nelis. though it is not to be con- 

 sidered a common or serious pear disease. 

 On account of the fact that the disease 

 under discussion is confined almost en- 

 tirely to the Pacific Northwest, it has been 

 assumed by a number of investigators that 

 there was a native host on which the 

 fungus occurred previous to the intro- 

 duction of cultivated fruit, and that when 

 the apple was introduced into the North- 



