94 



bulbs in the soil, and although it has been grown for fifteen 

 months in pure culture, no signs of an ascigerous stage (the 

 spores of which would, under natural conditions, presumably 

 be air-borne) has developed. Garden sanitation, rotation of 

 crops, and the use of soil fungicides, are therefore required for 

 its control. It is hoped to publish results in the spring. 



Potato Disease.— Miss Owen continued her investigation on 

 Skin Spot of the potato. The fungus was isolated and shown 

 to be quite distinct from Sp? car i : a, where it had been previously 

 placed. Froin reports received through the Plant Disease 

 Survey the disease was found to develop very widely during the 

 winter of 1917-18 on many varieties, and is apparently increas- 

 ing in abundance. The fungus, however, does not succeed in 

 reaching the inner part of the tuber, being kept to the surface 

 layers by the repeated formation of layers of wound-cork by 

 the potato plant. A paper on the subject will be published 

 shortly. 



The Experimental Ground. 



A further portion of the ground was laid out in 1918 and 

 replanted with young fruit trees. A large part was again kept 

 under potatoes, and a variety of vegetables was grown for 

 experimental purposes. A 10 -rod tfc allotment plot " was 

 marked out and planted in order to obtain exact figures of the 

 yield, in connection with statistics for the allotment movement. 



In addition to the work on fungus diseases, a portion of the 

 ground was used by the Entomologist of the Board of Agri- 

 culture for Erit Fly experiments, and for the testing of insecti- 

 cides on various fruit trees. 



Of the fungus diseases, mention may be made of the 



following : 



Rust. — With a view to testing the theory of 



mj 



badly affected with Cronartium ribicola, were purchased in the 

 autumn of 1917. No support for the theory was obtained. The 

 growth made by these bushes in the spring was clean and show r ed 

 no signs of any rust pustules, and microscopic examination of 

 the buds and twigs, carried out in the laboratory in winter, 

 failed to reveal any trace of mycelium. 



Plans had also been made to test the value of spraying mix- 

 tures for controlling black currant rust. Spraying experiments 

 were therefore arranged to be carried out on plots in a plantation 

 near Norwich, which was very badly attacked last summer, as 

 well as at Kew. By arrangement with other workers, 1 per cent. 



was selected as a fungicide, Bordeaux mix- 

 ture and lime sulphur being tested elsewhere. The first spraying 

 was given on the Norwich plots on June 13th, a week or so 

 previous to the time at which an outbreak might be expected. 

 The results of the experiments were, however, negative, since, as 

 mentioned above, there was practically no outbreak of Cronar- 

 tium last season and all the plots remained clean. It was. 

 however, ascertained that 1 per cent. Burgundy mixture caused 

 no leaf injury. 



mixture 



