260 



Black Currant Eehvorm 



Experiments dealing with the infection of probable host plants. 



Having thus ascertained the lines along which migration proceeds, 

 it became possible to deal with the infection of probable host plants. 



The hosts chosen for the purpose were red currant and gooseberry, 

 which bush fruits are normally grown in a mixed plantation. From 

 a practical point of view, the question of interchange of hosts among 

 surrounding trees is important, for if such interchange could be proved, 

 it would necessitate remedial measures being extended to such hosts. 



It must be noted here that in point of time this series of experi- 

 ments was undertaken after the work on migration was complete. 

 It was not until the month of January that the experiments were 

 started and thus different conditions due to the advancing spring 

 were unavoidably introduced. 



The results obtained from such work are not entirely convincing. 

 Some features however are fairly consistent throughout the series 

 and they may therefore be of some value if they are not isolated from 

 observations made at the same time in the field. 



For the purposes of this experiment gooseberry and red currant 

 seedlings were raised under the sterile conditions of the previous experi- 

 ments and kept in the laboratory greenhouse under the conditions 

 found to favour migration, (i) in excessive moisture under bell- jars, 

 and (ii) uncovered and sprayed twice daily with a spray producer. 

 The number of buds experimented on and the duration of the experi- 

 ment were also those of the previous experiment, but inoculation was 

 restricted to the soil. 



At the termination of the experiment an examination of both 

 species of Kibes shewed that infection had taken place in much the 

 same proportion in both hosts. It was found that approximately 25 

 per cent, of infected buds occurred in those seedlings kept under the 



