76 AGRICULTURAL RESEARCH AND THE FARMER : 



" Die Back " of Plum Trees. — The die back of plums is a 

 serious disease which has also received some attention. Bacteria- 

 like bodies have been found in immense numbers in the diseased 

 tissue adjacent to the healthy region, and it may prove that 

 they play an important part in the production of the disease, 

 either directly or in association with a fungus which is also 

 frequently present. 



" Bud Rot " of Apple Trees. — Work is also in progress regard- 

 ing a disease of apple buds caused by a fungus of the genus 

 Fusarium, which is very destructive on certain varieties in 

 some districts. The trouble is not apparent until bud-bursting 

 time in the spring, and it has been generally supposed that 

 infection occurred about that time. It is now suspected that 

 infection takes place at a much eariier period, and accordingly 

 sprajdng experiments during the winter season have been initiated 

 for the control of this disease. 



" Shot-Hole Disease " of Peach and Other Stone Fruit Trees. — 

 A shot-hole leaf disease of peaches has during recent years been 

 prevalent and caused much damage to foliage. This has been 

 examined in some detail and found to be caused by Clasterosporium 

 carpophilum, a fungus hitherto unrecorded in this country. 

 Infection experiments have shown that this organism readily 

 produces similar leaf disease in other forms of stone fruits, such 

 as plums and cherries, and it is probable that it is relatively 

 common throughout the country. Control measures are under 

 investigation. Sulphur fungicides appear to be ineffective. 



Wilt of Michaelmas Daisies. — An obscure disease of Michael- 

 mas Daisies causing wilting and death of the shoots and serious 

 loss to raisers of these plants has been proved to be due to a 

 parasitic fungus which infects the woody parts of the stem. 

 The propagation from healthy stock has been found to be of 

 first importance in the control of this disease. 



School of Botany, Cambridge. 

 Silver Leaf Disease. — The ravages of this disease are so 

 serious and widespread that a special grant has for the last few 

 years been made by the Ministry to the Cambridge School of 

 Botany to defray the cost of an investigation of the subject. 

 The disease is caused by a fungus, Stereum purpureum, which 

 enters the tree through wounds, Uves in the stems, and by some 

 secretive action affects the living substances of the branch so 

 that the inner part of the leaves gets partially detached from 

 the epidermis, or " skin," thus causing an interference with the 



