94 



Report of State Board of Horticulture. 



and the writer since the fungus has been found to be the cause of serious 

 losses of apples kept in both common and cold storage. Pathological 

 work with rots of the fruit of the quince done the past season established 

 the relation of one of the rots of the quince to blackspot canker rot. 



The results of the investigations relative to the development and 

 action of the parasite, gives numerous important facts concerning the 

 disease which may be summed up as follows: 



Young cankers appear on the bark of the apple tree during November 

 and later, first appearing on the tender twigs, water sprouts and more 

 succulent two-year-old stems, later becoming conspicuous on the older 

 portions, appearing between early November and early February, 

 although the greater number do appear late in November to the middle 

 of December or a little later. The source of the infection is spore forms. 

 The spores, both ascospores (winter) and the conidia (summer), are 

 apparently responsible for these infections. A large series of germin- 

 ation tests with the conidia show, while they may mature and will 

 germinate the latter part of May and later throughout the season, that 

 germination seldom takes place under ordinary field conditions but may 

 be induced to do so at almost any time after the conidia are mature in 

 size by providing the necessary moisture and maintaining a suitable 

 temperature, which it is apparent these spores must have. The temper- 

 ature and moisture conditions present in November and later are appar- 

 ently the conditions best suited to the fungus as is evidenced by the 

 appearance of a greater or lesser number of minute, round, somewhat 

 depressed and dark colored areas which extend through the bark into 

 the sap wood beneath. The investigations of Professor Jackson have 

 also shown that the ascospores of this fungus are matured in the same 

 cankers in which the conidia develop, but following the development of 

 the conidial stage. It was proven that both conidia and ascospores thus 

 developed in their Order do induce the typical cankers. The relative 

 value of the two kinds of spores as distributive agents has not been 

 determined but it is evident that both play their part and are jointly 

 effective in the continuation of the disease on infested trees, the spread 

 to the bodies and fruit of other apple trees, the fruit of the quince, the 

 trunks and limbs of the prune, plum, pear and cherry. 



Of the facts discovered in the recent investigations, the occurrence 

 of the disease on stored fruit from orchards in which anthracnose canker 

 do not occur is the most surprising. 



The following count made by Mr. B. B. Pratt, of the Bureau of 

 Plant Industry, United States Department of Agriculture, on eight boxes 

 of extra fancy spitzenburgs gives a very good idea of how severe the 

 disease may become even upon fruit taken from well kept orchards as are 

 the orchards from which these apples were taken. 



Lot 



First inspection 



January 12 . 

 February 17 

 Maren 26 ... 

 May 10 



January 12 . 

 February 17 

 Maren 26 ... 

 May 10 



Percent 

 Deca.ved 



8.3 



62.5 

 69.2 

 89.1 



0.0 

 5.0 



16.4 



Second inspection 



Percent 

 Decayed 



Jauary 22 : :«».6 



February 27 ' 88.3 



April 5.. I 81.7 



May 20 '• 95.0 



January 22 5.0 



February 27 1 8.3 



April 5 I 7.1 



May 20 i's.i» 



