\(j'2 A Blossom Wilt avd Ckmher of Ajjjde Trees 



If the dead spurs are allowed to remain on the trees until the following 

 season the fungus appears at the surface of the spurs and over the 

 cankered areas during the winter and spring in the form of rounded 

 Monilia pustules which burst through the bark and produce numerous 

 chains of conidia (Fig. 1). 



The constant association of the Monilia with the Blossom Wilt and 

 the appearance of that fungus on the diseased spurs and cankers 

 obviously suggest that the . organism is responsible for the damage 

 done. The Monilia that is generally assumed by plant pathologists, 

 in this country and abroad, to attack the apple is Monilia fructigena 

 Pers. (= Sclerotinia fructigena Schroter). In its conidial form this is 

 the fungus that so readily attacks the ripening apple during the late 

 summer and often causes them to become "mummified." On such 

 apples the fungus is usually to be seen in the form of yellow pustules 

 which appear more or less in concentric circles over the diseased fiuit. 

 The form which I have hitherto always found to be associated with the 

 Blossom Wilt was found to be quite distinct from the typical Monilia 

 fructigena found on the fruit in summer and autumn, in the colour and 

 size of its pustules, in the dimensions of the conidia and in its habit 

 and growth on artificially prepared culture media. The pustules of 

 the Blossom Wilt fungus are in general smaller than in M. fructigena, 

 are grey rather than yellow in colour and the conidia they bear are 

 smaller. This grey Monilia of the apple conforms more nearly to 

 descriptions of Monilia cinerea Bon. (= Sclerotinia, cinerea Schroter) 

 which, according to those continental mycologists who recognise this 

 as a species distinct from M. fructigena. is the form responsible for the 

 majority of cases of Brown Rot in the "stone-fruit"' trees (i.e. plum, 

 cherry, damson etc.). 



II. Historical. 



In 1888 Sorauer(2i) pointed out that not only was Monilia destructive 

 to the apples themselves but that it could invade the woody tissue of 

 the twigs which were in consequence killed towards their tips, and since 

 that year frequent references to this "Zweigdiirre" have appeared in 

 continental phytopathological literature. This condition on apple trees 

 is generally attributed to M. fructigena, while a similar disease on cherry 

 trees is said to be caused by M. cinerea by those who recognise the two 

 as distinct species. 



Frank and Kruger(iO) in 1899 make reference to an outbreak of 

 Brown Rot on apple trees in the neighbourhood of Berlin ; on the 



