54 A " Wither Tip " of FJma Trees 



against four treated with the apple "blossom-wilt" form, and the conidia 

 of the culture used in the inoculations were more abundant, so there could 

 be no doubt therefore that conidia were successfully applied to the 

 stigmas. 



The progress of the disease was almost the same for both (the 

 "blossom- wilt" strain advanced a little more rapidly than the "wither 

 tip" strain) until the base of the pedicel was reached, then in the one 

 case the infected flower fell off without causing- any further injury, in the 

 other the flower not only remained in position hut the disease extended 

 from it into the tissues of the spur and affected the whole cluster of 

 flowers and leaves. 



In this connection it is to be remarked that Woroni)i(i2) in his 

 inoculation experiments with Monilia cinerea and M. frucligena was 

 unable to produce with M. cinerea any infection of apple flowers except 

 on the stigmas themselves. Thus he states^ : " Die Gonidien der Sclerotinia 

 cinerea wachsen auch unter der Einwirkung des Narbeiisaftes in Keim- 

 f aden aus, dieselben konnen aber nur den GrifTel etwas angreif en und sind 

 gar nicht im Stande weiter in die Apfelbliithe einzudringen." It is 

 probable therefore that Woronin worked with a strain of M. cinerea 

 obtained from either cherry or plum, since I have had no difficulty 

 whatever in infecting flowering spurs and branches of apple trees by 

 inoculating the stigmas of the flowers with a strain of M. cinerea from 

 an apple tree. 



Whether other strains of Monilia cinerea found on "stone-fruit "trees 

 behave as the "wither tip" strain used in the experiments has not yet 

 been determined and it is proposed to carry out other ex])eriments 

 to ascertain whether there are strains occurring on plums and cherries 

 capable of infecting the spurs of the apple through the flowers. The 

 economic aspect of this problem is involved in the fact that plum trees 

 are often interplanted with apple trees in mixed orchards and the 

 possibility of the former proving sources of infection for the latter or 

 vice versa is a point of importance to the fruit grower. 



As already stated the "wither tip" strain used was one which usually 

 remains quite hyaline when growing on prune-juice agar; others which 

 have been isolated have more nearly approached the apple "blossom- 

 wilt" form in that they produce a brown coloration when growing on 

 that medium; one in particular (strain g of the table on p. 35) is in 

 this respect practically indistinguishable fiom the apple strains. The 

 "wither tip" strains which have been isolated and cultivated all produce 



^ Loc. cit. p. 25. 



