A BLOSSOM WILT AND CANKER OF 

 APPLE TPvEES. 



i 



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



{Mycological Department, South- Eastern Agricultural College, 

 Wye, Kent.) 



(With Plates XXII— XXIV.) 

 CONTENTS. 



PAGE 



I. Introduction ...... ... 159 



II. Historical 162 



III. The Disease as observed on naturally infected trees . . . 165 



(a) Observations made in 1915 ...... 165 



(b) Observations made in 1916 ....;. 168 



(c) Comparison with other diseases producing a similar con- 



dition 172 



IV. The Blossom Wilt Fungus compared with other Monilias of Fruit 



Trees 173 



(re) Cultural Studies of Monilias found in this country . 173 



(b) Dimensions of Conidia 177 



(c) American Strains of Monilia ...... 180 



(d) Continental Strains of Monilia ..... 181 



(e) Nomenclature of the various forms .... 183 



V. Inoculation Experiments with Pure Cultures .... 185 



(a) Inoculation of apple flowers in the greenhouse . . 186 



(6) Inoculation of apple flowers in the plantation . . 192 



(c) Inoculation of twigs through wounds .... 195 



(d) Inoculation of the fruit ....... 195 



VI. Control Measures 198 



I. Introduction. 



During recent years many varieties of apples have been seriously 

 attacked by a disease which causes the wilting and death of the blossom, 

 frequently kills the twigs, and may produce cankers on the branches. 

 From information received at Wye College from various localities in 



11—2 



