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A ''WITHER TIP" OF PLUM TREES 



By H. WORMALD, M.Sc. (Lond.), A.R.C.Sc. 



{Mycological Department, South-Eastern Agricultural College, 



Wye, Kent.) 



(With Plates VII— IX.) 

 CONTENTS. 



PAGE 



I. General Observations ....... 28 



IT. The Fungus 31 



(«) Annual Cycle 31 



(h) Cultural Studies .... . 32 



(r) Dimensions of the Conidia ..... 34 



((/) Identity of the Fungus 3B 



III. Inoculation Experiments ....... 37 



(«) Inoculation of plum leaves ..... 3S 



{!>) Inoculation of plum flowers ..... 38 



(c) Inoculation of plums .44 



{(l) Inoculation of apple flowers ..... 49 



(e) Deductions from results of inoculation experiments . 53 



IV. Control Measures ........ 55 



V. Summary and Conclusions ...... 57 



I. GENERAL OBSERVATIONS. 



In the summer of 1916, during the course of an investigation into the 

 cause of, and means of controlling, a "Blossom Wilt" of apple trees 

 which proved to be due to Monilia cinerea Bon., the attention of the 

 writer was directed to the presence of a Monilia on certain withered 

 leaves and dead twigs of Victoria plum trees in the fruit plantation at 

 Wye College. On microscopic examination it was found that the fungus 

 was morphologically similar to that producing the " Blossom Wilt and 

 Canker" disease of apple trees. The colour of the pustules was the same 

 and the dimensions of the conidia when the two forms were found under 

 similar conditions were also in approximate agreement, but since the 

 mode of attack was quite different in the case of plum twigs it was 

 decided that the disease demanded special study. 



Observations made on the affected trees showed that loaves actually 

 bearing pustules of the fungus were not of very frequent occurrence, but 



